反射01 Class类的使用、动态加载类、类类型说明、获取类的信息
0 Java反射机制
反射（Reflection）是 Java 的高级特性之一，是框架实现的基础。
0.1 定义
Java 反射机制是在运行状态中，对于任意一个类，都能够知道这个类的所有属性和方法；对于任意一个对象，都能够调用它的任意一个方法和属性；这种动态获取的信息以及动态调用对象的方法的功能称为 Java 语言的反射机制。
一般而言，当用户使用一个类的时候，应该获取这个类，而后通过这个类实例化对象，但是使用反射则可以相反的通过对象获取类中的信息。
通俗的讲反射就是可以在程序运行的时候动态装载类，查看类的信息，生成对象，或操作生成的对象。它允许运行中的 Java 程序获取自身的信息，自己能看到自己，就像照镜子一样。【源自gitChat】
1 Class类的使用
1.1 扫盲知识点
在Java的世界里，万事万物都是对象【PS: 类也是一个对象】。
坑01：java语言中，静态成员、普通数据类型不是对象
技巧01：普通的数据类型虽然不是对象，但是普通的数据类型都有对应的包装类来让其转化成一个对象
技巧02：静态的成员是属于类的而不是属于对象的，所以静态的成员不是对象
技巧03：所有的类都是java.lang.Class的实例对象【there is a class name Class：Class类的实例就是所有的实例对象所属的类】
1.2 Class类实例的创建
任何一个类都是Class类的实例对象，Class类的实例对象有三种表示方式；
类也是一个实例对象，是Class类的实例对象，这个对象我们称为该类的类类型；
例如：我们创建一个名为Foo的类，Foo类就是Class类的实例对象，假设Foo类对应的Class类的实例名为c1，那么我们就称c1是Foo类的类类型
总结：类类型就是Class类的一个实例，而且一个类只能有一个类类型，也就是所一个类只能和一个Class对应；虽然可以通过三种方式创建一个Class实例，但是针对一个类而言这三种方式创建得到的Class实例都是相等的，因为一个类的类类型只能和一个Class的实例对象。（即：一个类通过三种方式创建的类类型其实是一样的）
技巧01：不同的类对应的类类型都不一样，同理，不同的类对应的Class类实例都不一样
技巧02：同一个类只有一个类类型，同理，同一个类只和一个Class类实例对应；所以，同一个类通过不同方式创建的类类型都是一样的
1.2.1 利用class创建
任何一个类都默认拥有一个名为class的静态成员变量，该类可以利用class静态成员去创建该类的类实例。
例如：创建了一个名为Foo的类，执行 Foo.class 就会创建一个 Class 的实例，我们把得到的Class实例命名为c1，这个c1就是Foo类对应的类类型
1.2.2 利用实例对象创建
如果已经得到了某个类的实例，那么可以调用这个实例的成员方法getClass去创建该实例所属类的类类型
例如：创建了一个名为Foo的类，根据Foo创建了一个Foo的实例对象foo，我们可以利用foo去调用getClass来创建Class类的一个实例c2，这个c2就是foo所属类Foo的类类型
1.2.3 利用Class类创建
Class类有一个静态方法forName，Class类可以利用这个静态方法创建一个Class实例；forName方法的参数是一个类的全名
例如：创建了一个类Foo，该类的全名为 demo06_reflect.case01_class.Foo ，那么就可以利 Class.forName("demo06_reflect.case01_class.Foo")
去创建一个Class类的实例c3，这个c3就是Foo类的类类型
package demo06_reflect.case01_class; /**
* @author 王杨帅
* @create 2018-08-03 21:43
* @desc Class的使用
**/
public class Demo01_Class { public static void main(String[] args) { // 创建Foo类的一个实例foo, Foo是foo的实例类型，foo是Foo的一个实例
Foo foo = new Foo(); // Class实例创建01：利用静态成员calss创建
Class c1 = Foo.class; // Class实例创建02：利用实例成员ngetClass创建
Class c2 = foo.getClass(); // 因为一个类只和一个Class实例对应，所以结果为true
System.out.println(c1 == c2); // Class实例创建03：利用Class类的静态成员forName创建
try {
Class c3 = Class.forName("demo06_reflect.case01_class.Foo");
System.out.println(c1 == c3);
} catch (ClassNotFoundException e) {
e.printStackTrace();
} } } class Foo {
public String name = "warrio";
public void pirnt() {
System.out.println("foo");
}
}
1.3 Class类实例的作用
可以利用Class类实例去创建对应类的实例
例如：c1是Foo类对应的Class实例（即：c1是Foo类的类类型），那么可以调用c1的实例方法newInstance去创建一个Foo实例foo，此时Foo类就称为foo实例的实例类型
技巧01：通过Class实例创建该实例对应类的实例是必须进行类型转换，因为Class实例创建出来的实例类型都是Object类型的；而且还必须进行异常处理
技巧02：Class实例对应的类必须拥有无参构造器【PS: 有参构造器会覆盖默认的无参构造器】
package demo06_reflect.case01_class; /**
* @author 王杨帅
* @create 2018-08-03 21:43
* @desc Class的使用
**/
public class Demo01_Class { public static void main(String[] args) { try {
Foo foo = (Foo) Foo.class.newInstance();
foo.print();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} } } class Foo {
public String name = "warrio";
public void print() {
System.out.println("foo");
} public Foo() {
} public Foo(String name) {
this.name = name;
}
}
1.4 代码汇总
package demo06_reflect.case01_class; /**
* @author 王杨帅
* @create 2018-08-03 21:43
* @desc Class的使用
**/
public class Demo01_Class { public static void main(String[] args) { // Foo实例的表示
Foo f1 = new Foo(); // Foo也是一个实例对象【Foo类是Class类的实例对象】 /**
* 任何一个类都是Class类的实例对象，Class类的实例对象有三种表示方式
*/
// Class实例的表示01：任何一个类都有一个隐含的静态成员变量class
Class c1 = Foo.class; // Class实例的表示02：任何一个实例对象通过getClass方法就可以创建出一个Class类的实例
Class c2 = f1.getClass(); /**
* c1 c2 表示了Foo类的类类型（class type）
* 类也是一个实例对象，是Class类的实例对象；这个对象我们成为该类的类类型
* 【类类型就是Class类的一个实例对象，而且一个类类型只能和一个Class的实例对应】
*/ // c1 和 c2 都代表了Foo类的类类型，一个类只可能是Class类的一个实例对象
System.out.println(c1 == c2); // Class实例的表示03：直接利用 Class 类的 forName 静态方法实现
try {
Class c3 = Class.forName("demo06_reflect.case01_class.Foo");
} catch (ClassNotFoundException e) {
e.printStackTrace();
} // 04 可以利用该类的类类型创建该类的对象【通过c1/c2/c3创建Foo的实例】
// 前提：Foo类必须拥有无参数的构造方法
try {
Foo f2 = (Foo) c2.newInstance();
f2.print();
} catch (InstantiationException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} Class c = Foo2.class;
System.out.println(c1 == c); } } class Foo {
void print(){
System.out.println("foo");
}
} class Foo2 {}
2 动态加载类
2.1 扫盲知识点
Class.forName("类的全名") 不仅表示了类的类类型，还代表了动态加载类；
编译时刻加载类是静态加载类，运行时刻加载类是动态加载类 。
2.2 静态加载测试
2.2.1 需求
根据主函数中的参数创建对应的实例，并调用实例的方法
2.2.2 代码实现
public class Office {
public static void main(String[] args) {
System.out.println("Hello Boy");
if ("Word".equals(args[0])) {
Word word = new Word();
word.start();
}
if ("Excel".equals(args[0])) {
Excel excel = new Excel();
excel.start();
}
}
}
Office.java
2.2.3 编译
进入到存放源文件的文件夹，执行 javac "源文件名.java" 就可以对源文件进行编译
2.2.4 编译报错原因
在源代码中需要用到 Word 和 Excel 两个类，所以这两个类必须存在，而且必须经过编译
技巧01：因为源代码中是利用 new 关键字进行实例创建的，这种方式是静态加载类的方式，所以用到的类必须存在而且编译好的
技巧02：执行 javac Office.java 时会自动编译 Word.java、Excel.java 两个文件【PS: 前提是存在】
public class Word {
public void start() {
System.out.println("Word start...");
}
}
Word.java
public class Excel {
public void start() {
System.out.println("Excel start...");
}
}
Excel.java
2.2.5 运行测试
运行 Office 时，传入 Word 或者 Excel ，查看效果：
例如： java Office Word
2.3 静态加载的缺点
需要进行静态加载的类必须存在，如果有一个不存在的话就会导致整个代码编译失败
例如：删掉Excel类，再次执行 javac Office.java
2.4 动态加载类的作用
技巧01根据类的全名去动态加载类是在运行期间进行的
2.4.1 需求
根据不同的类名称去动态加载不同的类，让后调用该类的实例【PS: 这里的不同类指的是实现了同一接口的不同实现类】
2.4.2 思路
》定义一个OfficeAble接口，让Word和Excel都实现这个接口
》通过Class.fromName来动态加载类得到的类类型
》通过类类型去创建实例，将的到的实例类型指定为OfficeAble类型
》利用多态的特性去调用实例的方法
2.4.3 代码改进
技巧01：动态加载用到的类需要提前编译好，不然运行时会找不到需要的文件
技巧02：动态加载类可以根据不同的参数动态加载不同的实现类
public interface OfficeAble {
void start();
}
OfficeAble.java
public class Word implements OfficeAble {
public void start() {
System.out.println("Word start...");
}
}
Word.java
public class Excel implements OfficeAble {
public void start() {
System.out.println("Excel start...");
}
}
Excel.java
public class OfficeBetter {
public static void main(String[] args) {
try {
Class c = Class.forName(args[0]);
OfficeAble officeAble = (OfficeAble)c.newInstance();
officeAble.start();
} catch (Exception e) {
e.printStackTrace();
}
}
}
OfficeBetter.java
2.5 动态加载使用场景
业务功能更新，某个业务需要更新时，只需要一个重新实现了该业务接口的类，将其进行编译后，程序调用时修改调用的类名即可，这样就可以通过类的动态加载来实现局部业务的更新。
3 类类型说明
除了类拥有类类型外，基本的数据类型也拥有类类型。
技巧01：基本类型和基本类型对应的包装类型各自都有各自的类类型
package demo06_reflect.case03_method; /**
* @author 王杨帅
* @create 2018-08-05 22:25
* @desc 基本类型和void都有类类型
**/
public class Demo01 { public static void main(String[] args) {
Class c1 = int.class;
System.out.println(c1.getName()); Class c2 = Integer.class;
System.out.println(c2.getName()); Class c3 = void.class;
System.out.println(c3.getName()); Class c4 = Void.class;
System.out.println(c4.getName());
} }
4 获取类的信息
通过一个类的类型可以获取到该类的所有信息，详情可以参见Class源码
/*
* Copyright (c) 1994, 2014, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*
*/ package java.lang; import java.lang.reflect.AnnotatedElement;
import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.GenericDeclaration;
import java.lang.reflect.Member;
import java.lang.reflect.Field;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.lang.reflect.Constructor;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.AnnotatedType;
import java.lang.ref.SoftReference;
import java.io.InputStream;
import java.io.ObjectStreamField;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Set;
import java.util.Map;
import java.util.HashMap;
import java.util.Objects;
import sun.misc.Unsafe;
import sun.reflect.CallerSensitive;
import sun.reflect.ConstantPool;
import sun.reflect.Reflection;
import sun.reflect.ReflectionFactory;
import sun.reflect.generics.factory.CoreReflectionFactory;
import sun.reflect.generics.factory.GenericsFactory;
import sun.reflect.generics.repository.ClassRepository;
import sun.reflect.generics.repository.MethodRepository;
import sun.reflect.generics.repository.ConstructorRepository;
import sun.reflect.generics.scope.ClassScope;
import sun.security.util.SecurityConstants;
import java.lang.annotation.Annotation;
import java.lang.reflect.Proxy;
import sun.reflect.annotation.*;
import sun.reflect.misc.ReflectUtil; /**
* Instances of the class {@code Class} represent classes and
* interfaces in a running Java application. An enum is a kind of
* class and an annotation is a kind of interface. Every array also
* belongs to a class that is reflected as a {@code Class} object
* that is shared by all arrays with the same element type and number
* of dimensions. The primitive Java types ({@code boolean},
* {@code byte}, {@code char}, {@code short},
* {@code int}, {@code long}, {@code float}, and
* {@code double}), and the keyword {@code void} are also
* represented as {@code Class} objects.
*
* <p> {@code Class} has no public constructor. Instead {@code Class}
* objects are constructed automatically by the Java Virtual Machine as classes
* are loaded and by calls to the {@code defineClass} method in the class
* loader.
*
* <p> The following example uses a {@code Class} object to print the
* class name of an object:
*
* <blockquote><pre>
* void printClassName(Object obj) {
* System.out.println("The class of " + obj +
* " is " + obj.getClass().getName());
* }
* </pre></blockquote>
*
* <p> It is also possible to get the {@code Class} object for a named
* type (or for void) using a class literal. See Section 15.8.2 of
* <cite>The Java™ Language Specification</cite>.
* For example:
*
* <blockquote>
* {@code System.out.println("The name of class Foo is: "+Foo.class.getName());}
* </blockquote>
*
* @param <T> the type of the class modeled by this {@code Class}
* object. For example, the type of {@code String.class} is {@code
* Class<String>}. Use {@code Class<?>} if the class being modeled is
* unknown.
*
* @author unascribed
* @see java.lang.ClassLoader#defineClass(byte[], int, int)
* @since JDK1.0
*/
public final class Class<T> implements java.io.Serializable,
GenericDeclaration,
Type,
AnnotatedElement {
private static final int ANNOTATION= 0x00002000;
private static final int ENUM = 0x00004000;
private static final int SYNTHETIC = 0x00001000; private static native void registerNatives();
static {
registerNatives();
} /*
* Private constructor. Only the Java Virtual Machine creates Class objects.
* This constructor is not used and prevents the default constructor being
* generated.
*/
private Class(ClassLoader loader) {
// Initialize final field for classLoader. The initialization value of non-null
// prevents future JIT optimizations from assuming this final field is null.
classLoader = loader;
} /**
* Converts the object to a string. The string representation is the
* string "class" or "interface", followed by a space, and then by the
* fully qualified name of the class in the format returned by
* {@code getName}. If this {@code Class} object represents a
* primitive type, this method returns the name of the primitive type. If
* this {@code Class} object represents void this method returns
* "void".
*
* @return a string representation of this class object.
*/
public String toString() {
return (isInterface() ? "interface " : (isPrimitive() ? "" : "class "))
+ getName();
} /**
* Returns a string describing this {@code Class}, including
* information about modifiers and type parameters.
*
* The string is formatted as a list of type modifiers, if any,
* followed by the kind of type (empty string for primitive types
* and {@code class}, {@code enum}, {@code interface}, or
* <code>@</code>{@code interface}, as appropriate), followed
* by the type's name, followed by an angle-bracketed
* comma-separated list of the type's type parameters, if any.
*
* A space is used to separate modifiers from one another and to
* separate any modifiers from the kind of type. The modifiers
* occur in canonical order. If there are no type parameters, the
* type parameter list is elided.
*
* <p>Note that since information about the runtime representation
* of a type is being generated, modifiers not present on the
* originating source code or illegal on the originating source
* code may be present.
*
* @return a string describing this {@code Class}, including
* information about modifiers and type parameters
*
* @since 1.8
*/
public String toGenericString() {
if (isPrimitive()) {
return toString();
} else {
StringBuilder sb = new StringBuilder(); // Class modifiers are a superset of interface modifiers
int modifiers = getModifiers() & Modifier.classModifiers();
if (modifiers != 0) {
sb.append(Modifier.toString(modifiers));
sb.append(' ');
} if (isAnnotation()) {
sb.append('@');
}
if (isInterface()) { // Note: all annotation types are interfaces
sb.append("interface");
} else {
if (isEnum())
sb.append("enum");
else
sb.append("class");
}
sb.append(' ');
sb.append(getName()); TypeVariable<?>[] typeparms = getTypeParameters();
if (typeparms.length > 0) {
boolean first = true;
sb.append('<');
for(TypeVariable<?> typeparm: typeparms) {
if (!first)
sb.append(',');
sb.append(typeparm.getTypeName());
first = false;
}
sb.append('>');
} return sb.toString();
}
} /**
* Returns the {@code Class} object associated with the class or
* interface with the given string name. Invoking this method is
* equivalent to:
*
* <blockquote>
* {@code Class.forName(className, true, currentLoader)}
* </blockquote>
*
* where {@code currentLoader} denotes the defining class loader of
* the current class.
*
* <p> For example, the following code fragment returns the
* runtime {@code Class} descriptor for the class named
* {@code java.lang.Thread}:
*
* <blockquote>
* {@code Class t = Class.forName("java.lang.Thread")}
* </blockquote>
* <p>
* A call to {@code forName("X")} causes the class named
* {@code X} to be initialized.
*
* @param className the fully qualified name of the desired class.
* @return the {@code Class} object for the class with the
* specified name.
* @exception LinkageError if the linkage fails
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails
* @exception ClassNotFoundException if the class cannot be located
*/
@CallerSensitive
public static Class<?> forName(String className)
throws ClassNotFoundException {
Class<?> caller = Reflection.getCallerClass();
return forName0(className, true, ClassLoader.getClassLoader(caller), caller);
} /**
* Returns the {@code Class} object associated with the class or
* interface with the given string name, using the given class loader.
* Given the fully qualified name for a class or interface (in the same
* format returned by {@code getName}) this method attempts to
* locate, load, and link the class or interface. The specified class
* loader is used to load the class or interface. If the parameter
* {@code loader} is null, the class is loaded through the bootstrap
* class loader. The class is initialized only if the
* {@code initialize} parameter is {@code true} and if it has
* not been initialized earlier.
*
* <p> If {@code name} denotes a primitive type or void, an attempt
* will be made to locate a user-defined class in the unnamed package whose
* name is {@code name}. Therefore, this method cannot be used to
* obtain any of the {@code Class} objects representing primitive
* types or void.
*
* <p> If {@code name} denotes an array class, the component type of
* the array class is loaded but not initialized.
*
* <p> For example, in an instance method the expression:
*
* <blockquote>
* {@code Class.forName("Foo")}
* </blockquote>
*
* is equivalent to:
*
* <blockquote>
* {@code Class.forName("Foo", true, this.getClass().getClassLoader())}
* </blockquote>
*
* Note that this method throws errors related to loading, linking or
* initializing as specified in Sections 12.2, 12.3 and 12.4 of <em>The
* Java Language Specification</em>.
* Note that this method does not check whether the requested class
* is accessible to its caller.
*
* <p> If the {@code loader} is {@code null}, and a security
* manager is present, and the caller's class loader is not null, then this
* method calls the security manager's {@code checkPermission} method
* with a {@code RuntimePermission("getClassLoader")} permission to
* ensure it's ok to access the bootstrap class loader.
*
* @param name fully qualified name of the desired class
* @param initialize if {@code true} the class will be initialized.
* See Section 12.4 of <em>The Java Language Specification</em>.
* @param loader class loader from which the class must be loaded
* @return class object representing the desired class
*
* @exception LinkageError if the linkage fails
* @exception ExceptionInInitializerError if the initialization provoked
* by this method fails
* @exception ClassNotFoundException if the class cannot be located by
* the specified class loader
*
* @see java.lang.Class#forName(String)
* @see java.lang.ClassLoader
* @since 1.2
*/
@CallerSensitive
public static Class<?> forName(String name, boolean initialize,
ClassLoader loader)
throws ClassNotFoundException
{
Class<?> caller = null;
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
// Reflective call to get caller class is only needed if a security manager
// is present. Avoid the overhead of making this call otherwise.
caller = Reflection.getCallerClass();
if (sun.misc.VM.isSystemDomainLoader(loader)) {
ClassLoader ccl = ClassLoader.getClassLoader(caller);
if (!sun.misc.VM.isSystemDomainLoader(ccl)) {
sm.checkPermission(
SecurityConstants.GET_CLASSLOADER_PERMISSION);
}
}
}
return forName0(name, initialize, loader, caller);
} /** Called after security check for system loader access checks have been made. */
private static native Class<?> forName0(String name, boolean initialize,
ClassLoader loader,
Class<?> caller)
throws ClassNotFoundException; /**
* Creates a new instance of the class represented by this {@code Class}
* object. The class is instantiated as if by a {@code new}
* expression with an empty argument list. The class is initialized if it
* has not already been initialized.
*
* <p>Note that this method propagates any exception thrown by the
* nullary constructor, including a checked exception. Use of
* this method effectively bypasses the compile-time exception
* checking that would otherwise be performed by the compiler.
* The {@link
* java.lang.reflect.Constructor#newInstance(java.lang.Object...)
* Constructor.newInstance} method avoids this problem by wrapping
* any exception thrown by the constructor in a (checked) {@link
* java.lang.reflect.InvocationTargetException}.
*
* @return a newly allocated instance of the class represented by this
* object.
* @throws IllegalAccessException if the class or its nullary
* constructor is not accessible.
* @throws InstantiationException
* if this {@code Class} represents an abstract class,
* an interface, an array class, a primitive type, or void;
* or if the class has no nullary constructor;
* or if the instantiation fails for some other reason.
* @throws ExceptionInInitializerError if the initialization
* provoked by this method fails.
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*/
@CallerSensitive
public T newInstance()
throws InstantiationException, IllegalAccessException
{
if (System.getSecurityManager() != null) {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), false);
} // NOTE: the following code may not be strictly correct under
// the current Java memory model. // Constructor lookup
if (cachedConstructor == null) {
if (this == Class.class) {
throw new IllegalAccessException(
"Can not call newInstance() on the Class for java.lang.Class"
);
}
try {
Class<?>[] empty = {};
final Constructor<T> c = getConstructor0(empty, Member.DECLARED);
// Disable accessibility checks on the constructor
// since we have to do the security check here anyway
// (the stack depth is wrong for the Constructor's
// security check to work)
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Void>() {
public Void run() {
c.setAccessible(true);
return null;
}
});
cachedConstructor = c;
} catch (NoSuchMethodException e) {
throw (InstantiationException)
new InstantiationException(getName()).initCause(e);
}
}
Constructor<T> tmpConstructor = cachedConstructor;
// Security check (same as in java.lang.reflect.Constructor)
int modifiers = tmpConstructor.getModifiers();
if (!Reflection.quickCheckMemberAccess(this, modifiers)) {
Class<?> caller = Reflection.getCallerClass();
if (newInstanceCallerCache != caller) {
Reflection.ensureMemberAccess(caller, this, null, modifiers);
newInstanceCallerCache = caller;
}
}
// Run constructor
try {
return tmpConstructor.newInstance((Object[])null);
} catch (InvocationTargetException e) {
Unsafe.getUnsafe().throwException(e.getTargetException());
// Not reached
return null;
}
}
private volatile transient Constructor<T> cachedConstructor;
private volatile transient Class<?> newInstanceCallerCache; /**
* Determines if the specified {@code Object} is assignment-compatible
* with the object represented by this {@code Class}. This method is
* the dynamic equivalent of the Java language {@code instanceof}
* operator. The method returns {@code true} if the specified
* {@code Object} argument is non-null and can be cast to the
* reference type represented by this {@code Class} object without
* raising a {@code ClassCastException.} It returns {@code false}
* otherwise.
*
* <p> Specifically, if this {@code Class} object represents a
* declared class, this method returns {@code true} if the specified
* {@code Object} argument is an instance of the represented class (or
* of any of its subclasses); it returns {@code false} otherwise. If
* this {@code Class} object represents an array class, this method
* returns {@code true} if the specified {@code Object} argument
* can be converted to an object of the array class by an identity
* conversion or by a widening reference conversion; it returns
* {@code false} otherwise. If this {@code Class} object
* represents an interface, this method returns {@code true} if the
* class or any superclass of the specified {@code Object} argument
* implements this interface; it returns {@code false} otherwise. If
* this {@code Class} object represents a primitive type, this method
* returns {@code false}.
*
* @param obj the object to check
* @return true if {@code obj} is an instance of this class
*
* @since JDK1.1
*/
public native boolean isInstance(Object obj); /**
* Determines if the class or interface represented by this
* {@code Class} object is either the same as, or is a superclass or
* superinterface of, the class or interface represented by the specified
* {@code Class} parameter. It returns {@code true} if so;
* otherwise it returns {@code false}. If this {@code Class}
* object represents a primitive type, this method returns
* {@code true} if the specified {@code Class} parameter is
* exactly this {@code Class} object; otherwise it returns
* {@code false}.
*
* <p> Specifically, this method tests whether the type represented by the
* specified {@code Class} parameter can be converted to the type
* represented by this {@code Class} object via an identity conversion
* or via a widening reference conversion. See <em>The Java Language
* Specification</em>, sections 5.1.1 and 5.1.4 , for details.
*
* @param cls the {@code Class} object to be checked
* @return the {@code boolean} value indicating whether objects of the
* type {@code cls} can be assigned to objects of this class
* @exception NullPointerException if the specified Class parameter is
* null.
* @since JDK1.1
*/
public native boolean isAssignableFrom(Class<?> cls); /**
* Determines if the specified {@code Class} object represents an
* interface type.
*
* @return {@code true} if this object represents an interface;
* {@code false} otherwise.
*/
public native boolean isInterface(); /**
* Determines if this {@code Class} object represents an array class.
*
* @return {@code true} if this object represents an array class;
* {@code false} otherwise.
* @since JDK1.1
*/
public native boolean isArray(); /**
* Determines if the specified {@code Class} object represents a
* primitive type.
*
* <p> There are nine predefined {@code Class} objects to represent
* the eight primitive types and void. These are created by the Java
* Virtual Machine, and have the same names as the primitive types that
* they represent, namely {@code boolean}, {@code byte},
* {@code char}, {@code short}, {@code int},
* {@code long}, {@code float}, and {@code double}.
*
* <p> These objects may only be accessed via the following public static
* final variables, and are the only {@code Class} objects for which
* this method returns {@code true}.
*
* @return true if and only if this class represents a primitive type
*
* @see java.lang.Boolean#TYPE
* @see java.lang.Character#TYPE
* @see java.lang.Byte#TYPE
* @see java.lang.Short#TYPE
* @see java.lang.Integer#TYPE
* @see java.lang.Long#TYPE
* @see java.lang.Float#TYPE
* @see java.lang.Double#TYPE
* @see java.lang.Void#TYPE
* @since JDK1.1
*/
public native boolean isPrimitive(); /**
* Returns true if this {@code Class} object represents an annotation
* type. Note that if this method returns true, {@link #isInterface()}
* would also return true, as all annotation types are also interfaces.
*
* @return {@code true} if this class object represents an annotation
* type; {@code false} otherwise
* @since 1.5
*/
public boolean isAnnotation() {
return (getModifiers() & ANNOTATION) != 0;
} /**
* Returns {@code true} if this class is a synthetic class;
* returns {@code false} otherwise.
* @return {@code true} if and only if this class is a synthetic class as
* defined by the Java Language Specification.
* @jls 13.1 The Form of a Binary
* @since 1.5
*/
public boolean isSynthetic() {
return (getModifiers() & SYNTHETIC) != 0;
} /**
* Returns the name of the entity (class, interface, array class,
* primitive type, or void) represented by this {@code Class} object,
* as a {@code String}.
*
* <p> If this class object represents a reference type that is not an
* array type then the binary name of the class is returned, as specified
* by
* <cite>The Java™ Language Specification</cite>.
*
* <p> If this class object represents a primitive type or void, then the
* name returned is a {@code String} equal to the Java language
* keyword corresponding to the primitive type or void.
*
* <p> If this class object represents a class of arrays, then the internal
* form of the name consists of the name of the element type preceded by
* one or more '{@code [}' characters representing the depth of the array
* nesting. The encoding of element type names is as follows:
*
* <blockquote><table summary="Element types and encodings">
* <tr><th> Element Type <th> <th> Encoding
* <tr><td> boolean <td> <td align=center> Z
* <tr><td> byte <td> <td align=center> B
* <tr><td> char <td> <td align=center> C
* <tr><td> class or interface
* <td> <td align=center> L<i>classname</i>;
* <tr><td> double <td> <td align=center> D
* <tr><td> float <td> <td align=center> F
* <tr><td> int <td> <td align=center> I
* <tr><td> long <td> <td align=center> J
* <tr><td> short <td> <td align=center> S
* </table></blockquote>
*
* <p> The class or interface name <i>classname</i> is the binary name of
* the class specified above.
*
* <p> Examples:
* <blockquote><pre>
* String.class.getName()
* returns "java.lang.String"
* byte.class.getName()
* returns "byte"
* (new Object[3]).getClass().getName()
* returns "[Ljava.lang.Object;"
* (new int[3][4][5][6][7][8][9]).getClass().getName()
* returns "[[[[[[[I"
* </pre></blockquote>
*
* @return the name of the class or interface
* represented by this object.
*/
public String getName() {
String name = this.name;
if (name == null)
this.name = name = getName0();
return name;
} // cache the name to reduce the number of calls into the VM
private transient String name;
private native String getName0(); /**
* Returns the class loader for the class. Some implementations may use
* null to represent the bootstrap class loader. This method will return
* null in such implementations if this class was loaded by the bootstrap
* class loader.
*
* <p> If a security manager is present, and the caller's class loader is
* not null and the caller's class loader is not the same as or an ancestor of
* the class loader for the class whose class loader is requested, then
* this method calls the security manager's {@code checkPermission}
* method with a {@code RuntimePermission("getClassLoader")}
* permission to ensure it's ok to access the class loader for the class.
*
* <p>If this object
* represents a primitive type or void, null is returned.
*
* @return the class loader that loaded the class or interface
* represented by this object.
* @throws SecurityException
* if a security manager exists and its
* {@code checkPermission} method denies
* access to the class loader for the class.
* @see java.lang.ClassLoader
* @see SecurityManager#checkPermission
* @see java.lang.RuntimePermission
*/
@CallerSensitive
public ClassLoader getClassLoader() {
ClassLoader cl = getClassLoader0();
if (cl == null)
return null;
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
ClassLoader.checkClassLoaderPermission(cl, Reflection.getCallerClass());
}
return cl;
} // Package-private to allow ClassLoader access
ClassLoader getClassLoader0() { return classLoader; } // Initialized in JVM not by private constructor
// This field is filtered from reflection access, i.e. getDeclaredField
// will throw NoSuchFieldException
private final ClassLoader classLoader; /**
* Returns an array of {@code TypeVariable} objects that represent the
* type variables declared by the generic declaration represented by this
* {@code GenericDeclaration} object, in declaration order. Returns an
* array of length 0 if the underlying generic declaration declares no type
* variables.
*
* @return an array of {@code TypeVariable} objects that represent
* the type variables declared by this generic declaration
* @throws java.lang.reflect.GenericSignatureFormatError if the generic
* signature of this generic declaration does not conform to
* the format specified in
* <cite>The Java™ Virtual Machine Specification</cite>
* @since 1.5
*/
@SuppressWarnings("unchecked")
public TypeVariable<Class<T>>[] getTypeParameters() {
ClassRepository info = getGenericInfo();
if (info != null)
return (TypeVariable<Class<T>>[])info.getTypeParameters();
else
return (TypeVariable<Class<T>>[])new TypeVariable<?>[0];
} /**
* Returns the {@code Class} representing the superclass of the entity
* (class, interface, primitive type or void) represented by this
* {@code Class}. If this {@code Class} represents either the
* {@code Object} class, an interface, a primitive type, or void, then
* null is returned. If this object represents an array class then the
* {@code Class} object representing the {@code Object} class is
* returned.
*
* @return the superclass of the class represented by this object.
*/
public native Class<? super T> getSuperclass(); /**
* Returns the {@code Type} representing the direct superclass of
* the entity (class, interface, primitive type or void) represented by
* this {@code Class}.
*
* <p>If the superclass is a parameterized type, the {@code Type}
* object returned must accurately reflect the actual type
* parameters used in the source code. The parameterized type
* representing the superclass is created if it had not been
* created before. See the declaration of {@link
* java.lang.reflect.ParameterizedType ParameterizedType} for the
* semantics of the creation process for parameterized types. If
* this {@code Class} represents either the {@code Object}
* class, an interface, a primitive type, or void, then null is
* returned. If this object represents an array class then the
* {@code Class} object representing the {@code Object} class is
* returned.
*
* @throws java.lang.reflect.GenericSignatureFormatError if the generic
* class signature does not conform to the format specified in
* <cite>The Java™ Virtual Machine Specification</cite>
* @throws TypeNotPresentException if the generic superclass
* refers to a non-existent type declaration
* @throws java.lang.reflect.MalformedParameterizedTypeException if the
* generic superclass refers to a parameterized type that cannot be
* instantiated for any reason
* @return the superclass of the class represented by this object
* @since 1.5
*/
public Type getGenericSuperclass() {
ClassRepository info = getGenericInfo();
if (info == null) {
return getSuperclass();
} // Historical irregularity:
// Generic signature marks interfaces with superclass = Object
// but this API returns null for interfaces
if (isInterface()) {
return null;
} return info.getSuperclass();
} /**
* Gets the package for this class. The class loader of this class is used
* to find the package. If the class was loaded by the bootstrap class
* loader the set of packages loaded from CLASSPATH is searched to find the
* package of the class. Null is returned if no package object was created
* by the class loader of this class.
*
* <p> Packages have attributes for versions and specifications only if the
* information was defined in the manifests that accompany the classes, and
* if the class loader created the package instance with the attributes
* from the manifest.
*
* @return the package of the class, or null if no package
* information is available from the archive or codebase.
*/
public Package getPackage() {
return Package.getPackage(this);
} /**
* Determines the interfaces implemented by the class or interface
* represented by this object.
*
* <p> If this object represents a class, the return value is an array
* containing objects representing all interfaces implemented by the
* class. The order of the interface objects in the array corresponds to
* the order of the interface names in the {@code implements} clause
* of the declaration of the class represented by this object. For
* example, given the declaration:
* <blockquote>
* {@code class Shimmer implements FloorWax, DessertTopping { ... }}
* </blockquote>
* suppose the value of {@code s} is an instance of
* {@code Shimmer}; the value of the expression:
* <blockquote>
* {@code s.getClass().getInterfaces()[0]}
* </blockquote>
* is the {@code Class} object that represents interface
* {@code FloorWax}; and the value of:
* <blockquote>
* {@code s.getClass().getInterfaces()[1]}
* </blockquote>
* is the {@code Class} object that represents interface
* {@code DessertTopping}.
*
* <p> If this object represents an interface, the array contains objects
* representing all interfaces extended by the interface. The order of the
* interface objects in the array corresponds to the order of the interface
* names in the {@code extends} clause of the declaration of the
* interface represented by this object.
*
* <p> If this object represents a class or interface that implements no
* interfaces, the method returns an array of length 0.
*
* <p> If this object represents a primitive type or void, the method
* returns an array of length 0.
*
* <p> If this {@code Class} object represents an array type, the
* interfaces {@code Cloneable} and {@code java.io.Serializable} are
* returned in that order.
*
* @return an array of interfaces implemented by this class.
*/
public Class<?>[] getInterfaces() {
ReflectionData<T> rd = reflectionData();
if (rd == null) {
// no cloning required
return getInterfaces0();
} else {
Class<?>[] interfaces = rd.interfaces;
if (interfaces == null) {
interfaces = getInterfaces0();
rd.interfaces = interfaces;
}
// defensively copy before handing over to user code
return interfaces.clone();
}
} private native Class<?>[] getInterfaces0(); /**
* Returns the {@code Type}s representing the interfaces
* directly implemented by the class or interface represented by
* this object.
*
* <p>If a superinterface is a parameterized type, the
* {@code Type} object returned for it must accurately reflect
* the actual type parameters used in the source code. The
* parameterized type representing each superinterface is created
* if it had not been created before. See the declaration of
* {@link java.lang.reflect.ParameterizedType ParameterizedType}
* for the semantics of the creation process for parameterized
* types.
*
* <p> If this object represents a class, the return value is an
* array containing objects representing all interfaces
* implemented by the class. The order of the interface objects in
* the array corresponds to the order of the interface names in
* the {@code implements} clause of the declaration of the class
* represented by this object. In the case of an array class, the
* interfaces {@code Cloneable} and {@code Serializable} are
* returned in that order.
*
* <p>If this object represents an interface, the array contains
* objects representing all interfaces directly extended by the
* interface. The order of the interface objects in the array
* corresponds to the order of the interface names in the
* {@code extends} clause of the declaration of the interface
* represented by this object.
*
* <p>If this object represents a class or interface that
* implements no interfaces, the method returns an array of length
* 0.
*
* <p>If this object represents a primitive type or void, the
* method returns an array of length 0.
*
* @throws java.lang.reflect.GenericSignatureFormatError
* if the generic class signature does not conform to the format
* specified in
* <cite>The Java™ Virtual Machine Specification</cite>
* @throws TypeNotPresentException if any of the generic
* superinterfaces refers to a non-existent type declaration
* @throws java.lang.reflect.MalformedParameterizedTypeException
* if any of the generic superinterfaces refer to a parameterized
* type that cannot be instantiated for any reason
* @return an array of interfaces implemented by this class
* @since 1.5
*/
public Type[] getGenericInterfaces() {
ClassRepository info = getGenericInfo();
return (info == null) ? getInterfaces() : info.getSuperInterfaces();
} /**
* Returns the {@code Class} representing the component type of an
* array. If this class does not represent an array class this method
* returns null.
*
* @return the {@code Class} representing the component type of this
* class if this class is an array
* @see java.lang.reflect.Array
* @since JDK1.1
*/
public native Class<?> getComponentType(); /**
* Returns the Java language modifiers for this class or interface, encoded
* in an integer. The modifiers consist of the Java Virtual Machine's
* constants for {@code public}, {@code protected},
* {@code private}, {@code final}, {@code static},
* {@code abstract} and {@code interface}; they should be decoded
* using the methods of class {@code Modifier}.
*
* <p> If the underlying class is an array class, then its
* {@code public}, {@code private} and {@code protected}
* modifiers are the same as those of its component type. If this
* {@code Class} represents a primitive type or void, its
* {@code public} modifier is always {@code true}, and its
* {@code protected} and {@code private} modifiers are always
* {@code false}. If this object represents an array class, a
* primitive type or void, then its {@code final} modifier is always
* {@code true} and its interface modifier is always
* {@code false}. The values of its other modifiers are not determined
* by this specification.
*
* <p> The modifier encodings are defined in <em>The Java Virtual Machine
* Specification</em>, table 4.1.
*
* @return the {@code int} representing the modifiers for this class
* @see java.lang.reflect.Modifier
* @since JDK1.1
*/
public native int getModifiers(); /**
* Gets the signers of this class.
*
* @return the signers of this class, or null if there are no signers. In
* particular, this method returns null if this object represents
* a primitive type or void.
* @since JDK1.1
*/
public native Object[] getSigners(); /**
* Set the signers of this class.
*/
native void setSigners(Object[] signers); /**
* If this {@code Class} object represents a local or anonymous
* class within a method, returns a {@link
* java.lang.reflect.Method Method} object representing the
* immediately enclosing method of the underlying class. Returns
* {@code null} otherwise.
*
* In particular, this method returns {@code null} if the underlying
* class is a local or anonymous class immediately enclosed by a type
* declaration, instance initializer or static initializer.
*
* @return the immediately enclosing method of the underlying class, if
* that class is a local or anonymous class; otherwise {@code null}.
*
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of the enclosing class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the methods within the enclosing class
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the enclosing class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of the enclosing class
*
* </ul>
* @since 1.5
*/
@CallerSensitive
public Method getEnclosingMethod() throws SecurityException {
EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo(); if (enclosingInfo == null)
return null;
else {
if (!enclosingInfo.isMethod())
return null; MethodRepository typeInfo = MethodRepository.make(enclosingInfo.getDescriptor(),
getFactory());
Class<?> returnType = toClass(typeInfo.getReturnType());
Type [] parameterTypes = typeInfo.getParameterTypes();
Class<?>[] parameterClasses = new Class<?>[parameterTypes.length]; // Convert Types to Classes; returned types *should*
// be class objects since the methodDescriptor's used
// don't have generics information
for(int i = 0; i < parameterClasses.length; i++)
parameterClasses[i] = toClass(parameterTypes[i]); // Perform access check
Class<?> enclosingCandidate = enclosingInfo.getEnclosingClass();
enclosingCandidate.checkMemberAccess(Member.DECLARED,
Reflection.getCallerClass(), true);
/*
* Loop over all declared methods; match method name,
* number of and type of parameters, *and* return
* type. Matching return type is also necessary
* because of covariant returns, etc.
*/
for(Method m: enclosingCandidate.getDeclaredMethods()) {
if (m.getName().equals(enclosingInfo.getName()) ) {
Class<?>[] candidateParamClasses = m.getParameterTypes();
if (candidateParamClasses.length == parameterClasses.length) {
boolean matches = true;
for(int i = 0; i < candidateParamClasses.length; i++) {
if (!candidateParamClasses[i].equals(parameterClasses[i])) {
matches = false;
break;
}
} if (matches) { // finally, check return type
if (m.getReturnType().equals(returnType) )
return m;
}
}
}
} throw new InternalError("Enclosing method not found");
}
} private native Object[] getEnclosingMethod0(); private EnclosingMethodInfo getEnclosingMethodInfo() {
Object[] enclosingInfo = getEnclosingMethod0();
if (enclosingInfo == null)
return null;
else {
return new EnclosingMethodInfo(enclosingInfo);
}
} private final static class EnclosingMethodInfo {
private Class<?> enclosingClass;
private String name;
private String descriptor; private EnclosingMethodInfo(Object[] enclosingInfo) {
if (enclosingInfo.length != 3)
throw new InternalError("Malformed enclosing method information");
try {
// The array is expected to have three elements: // the immediately enclosing class
enclosingClass = (Class<?>) enclosingInfo[0];
assert(enclosingClass != null); // the immediately enclosing method or constructor's
// name (can be null).
name = (String) enclosingInfo[1]; // the immediately enclosing method or constructor's
// descriptor (null iff name is).
descriptor = (String) enclosingInfo[2];
assert((name != null && descriptor != null) || name == descriptor);
} catch (ClassCastException cce) {
throw new InternalError("Invalid type in enclosing method information", cce);
}
} boolean isPartial() {
return enclosingClass == null || name == null || descriptor == null;
} boolean isConstructor() { return !isPartial() && "<init>".equals(name); } boolean isMethod() { return !isPartial() && !isConstructor() && !"<clinit>".equals(name); } Class<?> getEnclosingClass() { return enclosingClass; } String getName() { return name; } String getDescriptor() { return descriptor; } } private static Class<?> toClass(Type o) {
if (o instanceof GenericArrayType)
return Array.newInstance(toClass(((GenericArrayType)o).getGenericComponentType()),
0)
.getClass();
return (Class<?>)o;
} /**
* If this {@code Class} object represents a local or anonymous
* class within a constructor, returns a {@link
* java.lang.reflect.Constructor Constructor} object representing
* the immediately enclosing constructor of the underlying
* class. Returns {@code null} otherwise. In particular, this
* method returns {@code null} if the underlying class is a local
* or anonymous class immediately enclosed by a type declaration,
* instance initializer or static initializer.
*
* @return the immediately enclosing constructor of the underlying class, if
* that class is a local or anonymous class; otherwise {@code null}.
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of the enclosing class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the constructors within the enclosing class
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the enclosing class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of the enclosing class
*
* </ul>
* @since 1.5
*/
@CallerSensitive
public Constructor<?> getEnclosingConstructor() throws SecurityException {
EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo(); if (enclosingInfo == null)
return null;
else {
if (!enclosingInfo.isConstructor())
return null; ConstructorRepository typeInfo = ConstructorRepository.make(enclosingInfo.getDescriptor(),
getFactory());
Type [] parameterTypes = typeInfo.getParameterTypes();
Class<?>[] parameterClasses = new Class<?>[parameterTypes.length]; // Convert Types to Classes; returned types *should*
// be class objects since the methodDescriptor's used
// don't have generics information
for(int i = 0; i < parameterClasses.length; i++)
parameterClasses[i] = toClass(parameterTypes[i]); // Perform access check
Class<?> enclosingCandidate = enclosingInfo.getEnclosingClass();
enclosingCandidate.checkMemberAccess(Member.DECLARED,
Reflection.getCallerClass(), true);
/*
* Loop over all declared constructors; match number
* of and type of parameters.
*/
for(Constructor<?> c: enclosingCandidate.getDeclaredConstructors()) {
Class<?>[] candidateParamClasses = c.getParameterTypes();
if (candidateParamClasses.length == parameterClasses.length) {
boolean matches = true;
for(int i = 0; i < candidateParamClasses.length; i++) {
if (!candidateParamClasses[i].equals(parameterClasses[i])) {
matches = false;
break;
}
} if (matches)
return c;
}
} throw new InternalError("Enclosing constructor not found");
}
} /**
* If the class or interface represented by this {@code Class} object
* is a member of another class, returns the {@code Class} object
* representing the class in which it was declared. This method returns
* null if this class or interface is not a member of any other class. If
* this {@code Class} object represents an array class, a primitive
* type, or void,then this method returns null.
*
* @return the declaring class for this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and the caller's
* class loader is not the same as or an ancestor of the class
* loader for the declaring class and invocation of {@link
* SecurityManager#checkPackageAccess s.checkPackageAccess()}
* denies access to the package of the declaring class
* @since JDK1.1
*/
@CallerSensitive
public Class<?> getDeclaringClass() throws SecurityException {
final Class<?> candidate = getDeclaringClass0(); if (candidate != null)
candidate.checkPackageAccess(
ClassLoader.getClassLoader(Reflection.getCallerClass()), true);
return candidate;
} private native Class<?> getDeclaringClass0(); /**
* Returns the immediately enclosing class of the underlying
* class. If the underlying class is a top level class this
* method returns {@code null}.
* @return the immediately enclosing class of the underlying class
* @exception SecurityException
* If a security manager, <i>s</i>, is present and the caller's
* class loader is not the same as or an ancestor of the class
* loader for the enclosing class and invocation of {@link
* SecurityManager#checkPackageAccess s.checkPackageAccess()}
* denies access to the package of the enclosing class
* @since 1.5
*/
@CallerSensitive
public Class<?> getEnclosingClass() throws SecurityException {
// There are five kinds of classes (or interfaces):
// a) Top level classes
// b) Nested classes (static member classes)
// c) Inner classes (non-static member classes)
// d) Local classes (named classes declared within a method)
// e) Anonymous classes // JVM Spec 4.8.6: A class must have an EnclosingMethod
// attribute if and only if it is a local class or an
// anonymous class.
EnclosingMethodInfo enclosingInfo = getEnclosingMethodInfo();
Class<?> enclosingCandidate; if (enclosingInfo == null) {
// This is a top level or a nested class or an inner class (a, b, or c)
enclosingCandidate = getDeclaringClass();
} else {
Class<?> enclosingClass = enclosingInfo.getEnclosingClass();
// This is a local class or an anonymous class (d or e)
if (enclosingClass == this || enclosingClass == null)
throw new InternalError("Malformed enclosing method information");
else
enclosingCandidate = enclosingClass;
} if (enclosingCandidate != null)
enclosingCandidate.checkPackageAccess(
ClassLoader.getClassLoader(Reflection.getCallerClass()), true);
return enclosingCandidate;
} /**
* Returns the simple name of the underlying class as given in the
* source code. Returns an empty string if the underlying class is
* anonymous.
*
* <p>The simple name of an array is the simple name of the
* component type with "[]" appended. In particular the simple
* name of an array whose component type is anonymous is "[]".
*
* @return the simple name of the underlying class
* @since 1.5
*/
public String getSimpleName() {
if (isArray())
return getComponentType().getSimpleName()+"[]"; String simpleName = getSimpleBinaryName();
if (simpleName == null) { // top level class
simpleName = getName();
return simpleName.substring(simpleName.lastIndexOf(".")+1); // strip the package name
}
// According to JLS3 "Binary Compatibility" (13.1) the binary
// name of non-package classes (not top level) is the binary
// name of the immediately enclosing class followed by a '$' followed by:
// (for nested and inner classes): the simple name.
// (for local classes): 1 or more digits followed by the simple name.
// (for anonymous classes): 1 or more digits. // Since getSimpleBinaryName() will strip the binary name of
// the immediatly enclosing class, we are now looking at a
// string that matches the regular expression "\$[0-9]*"
// followed by a simple name (considering the simple of an
// anonymous class to be the empty string). // Remove leading "\$[0-9]*" from the name
int length = simpleName.length();
if (length < 1 || simpleName.charAt(0) != '$')
throw new InternalError("Malformed class name");
int index = 1;
while (index < length && isAsciiDigit(simpleName.charAt(index)))
index++;
// Eventually, this is the empty string iff this is an anonymous class
return simpleName.substring(index);
} /**
* Return an informative string for the name of this type.
*
* @return an informative string for the name of this type
* @since 1.8
*/
public String getTypeName() {
if (isArray()) {
try {
Class<?> cl = this;
int dimensions = 0;
while (cl.isArray()) {
dimensions++;
cl = cl.getComponentType();
}
StringBuilder sb = new StringBuilder();
sb.append(cl.getName());
for (int i = 0; i < dimensions; i++) {
sb.append("[]");
}
return sb.toString();
} catch (Throwable e) { /*FALLTHRU*/ }
}
return getName();
} /**
* Character.isDigit answers {@code true} to some non-ascii
* digits. This one does not.
*/
private static boolean isAsciiDigit(char c) {
return '0' <= c && c <= '9';
} /**
* Returns the canonical name of the underlying class as
* defined by the Java Language Specification. Returns null if
* the underlying class does not have a canonical name (i.e., if
* it is a local or anonymous class or an array whose component
* type does not have a canonical name).
* @return the canonical name of the underlying class if it exists, and
* {@code null} otherwise.
* @since 1.5
*/
public String getCanonicalName() {
if (isArray()) {
String canonicalName = getComponentType().getCanonicalName();
if (canonicalName != null)
return canonicalName + "[]";
else
return null;
}
if (isLocalOrAnonymousClass())
return null;
Class<?> enclosingClass = getEnclosingClass();
if (enclosingClass == null) { // top level class
return getName();
} else {
String enclosingName = enclosingClass.getCanonicalName();
if (enclosingName == null)
return null;
return enclosingName + "." + getSimpleName();
}
} /**
* Returns {@code true} if and only if the underlying class
* is an anonymous class.
*
* @return {@code true} if and only if this class is an anonymous class.
* @since 1.5
*/
public boolean isAnonymousClass() {
return "".equals(getSimpleName());
} /**
* Returns {@code true} if and only if the underlying class
* is a local class.
*
* @return {@code true} if and only if this class is a local class.
* @since 1.5
*/
public boolean isLocalClass() {
return isLocalOrAnonymousClass() && !isAnonymousClass();
} /**
* Returns {@code true} if and only if the underlying class
* is a member class.
*
* @return {@code true} if and only if this class is a member class.
* @since 1.5
*/
public boolean isMemberClass() {
return getSimpleBinaryName() != null && !isLocalOrAnonymousClass();
} /**
* Returns the "simple binary name" of the underlying class, i.e.,
* the binary name without the leading enclosing class name.
* Returns {@code null} if the underlying class is a top level
* class.
*/
private String getSimpleBinaryName() {
Class<?> enclosingClass = getEnclosingClass();
if (enclosingClass == null) // top level class
return null;
// Otherwise, strip the enclosing class' name
try {
return getName().substring(enclosingClass.getName().length());
} catch (IndexOutOfBoundsException ex) {
throw new InternalError("Malformed class name", ex);
}
} /**
* Returns {@code true} if this is a local class or an anonymous
* class. Returns {@code false} otherwise.
*/
private boolean isLocalOrAnonymousClass() {
// JVM Spec 4.8.6: A class must have an EnclosingMethod
// attribute if and only if it is a local class or an
// anonymous class.
return getEnclosingMethodInfo() != null;
} /**
* Returns an array containing {@code Class} objects representing all
* the public classes and interfaces that are members of the class
* represented by this {@code Class} object. This includes public
* class and interface members inherited from superclasses and public class
* and interface members declared by the class. This method returns an
* array of length 0 if this {@code Class} object has no public member
* classes or interfaces. This method also returns an array of length 0 if
* this {@code Class} object represents a primitive type, an array
* class, or void.
*
* @return the array of {@code Class} objects representing the public
* members of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @since JDK1.1
*/
@CallerSensitive
public Class<?>[] getClasses() {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), false); // Privileged so this implementation can look at DECLARED classes,
// something the caller might not have privilege to do. The code here
// is allowed to look at DECLARED classes because (1) it does not hand
// out anything other than public members and (2) public member access
// has already been ok'd by the SecurityManager. return java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Class<?>[]>() {
public Class<?>[] run() {
List<Class<?>> list = new ArrayList<>();
Class<?> currentClass = Class.this;
while (currentClass != null) {
Class<?>[] members = currentClass.getDeclaredClasses();
for (int i = 0; i < members.length; i++) {
if (Modifier.isPublic(members[i].getModifiers())) {
list.add(members[i]);
}
}
currentClass = currentClass.getSuperclass();
}
return list.toArray(new Class<?>[0]);
}
});
} /**
* Returns an array containing {@code Field} objects reflecting all
* the accessible public fields of the class or interface represented by
* this {@code Class} object.
*
* <p> If this {@code Class} object represents a class or interface with no
* no accessible public fields, then this method returns an array of length
* 0.
*
* <p> If this {@code Class} object represents a class, then this method
* returns the public fields of the class and of all its superclasses.
*
* <p> If this {@code Class} object represents an interface, then this
* method returns the fields of the interface and of all its
* superinterfaces.
*
* <p> If this {@code Class} object represents an array type, a primitive
* type, or void, then this method returns an array of length 0.
*
* <p> The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Field} objects representing the
* public fields
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @since JDK1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
@CallerSensitive
public Field[] getFields() throws SecurityException {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);
return copyFields(privateGetPublicFields(null));
} /**
* Returns an array containing {@code Method} objects reflecting all the
* public methods of the class or interface represented by this {@code
* Class} object, including those declared by the class or interface and
* those inherited from superclasses and superinterfaces.
*
* <p> If this {@code Class} object represents a type that has multiple
* public methods with the same name and parameter types, but different
* return types, then the returned array has a {@code Method} object for
* each such method.
*
* <p> If this {@code Class} object represents a type with a class
* initialization method {@code <clinit>}, then the returned array does
* <em>not</em> have a corresponding {@code Method} object.
*
* <p> If this {@code Class} object represents an array type, then the
* returned array has a {@code Method} object for each of the public
* methods inherited by the array type from {@code Object}. It does not
* contain a {@code Method} object for {@code clone()}.
*
* <p> If this {@code Class} object represents an interface then the
* returned array does not contain any implicitly declared methods from
* {@code Object}. Therefore, if no methods are explicitly declared in
* this interface or any of its superinterfaces then the returned array
* has length 0. (Note that a {@code Class} object which represents a class
* always has public methods, inherited from {@code Object}.)
*
* <p> If this {@code Class} object represents a primitive type or void,
* then the returned array has length 0.
*
* <p> Static methods declared in superinterfaces of the class or interface
* represented by this {@code Class} object are not considered members of
* the class or interface.
*
* <p> The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Method} objects representing the
* public methods of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since JDK1.1
*/
@CallerSensitive
public Method[] getMethods() throws SecurityException {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);
return copyMethods(privateGetPublicMethods());
} /**
* Returns an array containing {@code Constructor} objects reflecting
* all the public constructors of the class represented by this
* {@code Class} object. An array of length 0 is returned if the
* class has no public constructors, or if the class is an array class, or
* if the class reflects a primitive type or void.
*
* Note that while this method returns an array of {@code
* Constructor<T>} objects (that is an array of constructors from
* this class), the return type of this method is {@code
* Constructor<?>[]} and <em>not</em> {@code Constructor<T>[]} as
* might be expected. This less informative return type is
* necessary since after being returned from this method, the
* array could be modified to hold {@code Constructor} objects for
* different classes, which would violate the type guarantees of
* {@code Constructor<T>[]}.
*
* @return the array of {@code Constructor} objects representing the
* public constructors of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @since JDK1.1
*/
@CallerSensitive
public Constructor<?>[] getConstructors() throws SecurityException {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);
return copyConstructors(privateGetDeclaredConstructors(true));
} /**
* Returns a {@code Field} object that reflects the specified public member
* field of the class or interface represented by this {@code Class}
* object. The {@code name} parameter is a {@code String} specifying the
* simple name of the desired field.
*
* <p> The field to be reflected is determined by the algorithm that
* follows. Let C be the class or interface represented by this object:
*
* <OL>
* <LI> If C declares a public field with the name specified, that is the
* field to be reflected.</LI>
* <LI> If no field was found in step 1 above, this algorithm is applied
* recursively to each direct superinterface of C. The direct
* superinterfaces are searched in the order they were declared.</LI>
* <LI> If no field was found in steps 1 and 2 above, and C has a
* superclass S, then this algorithm is invoked recursively upon S.
* If C has no superclass, then a {@code NoSuchFieldException}
* is thrown.</LI>
* </OL>
*
* <p> If this {@code Class} object represents an array type, then this
* method does not find the {@code length} field of the array type.
*
* @param name the field name
* @return the {@code Field} object of this class specified by
* {@code name}
* @throws NoSuchFieldException if a field with the specified name is
* not found.
* @throws NullPointerException if {@code name} is {@code null}
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @since JDK1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
@CallerSensitive
public Field getField(String name)
throws NoSuchFieldException, SecurityException {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);
Field field = getField0(name);
if (field == null) {
throw new NoSuchFieldException(name);
}
return field;
} /**
* Returns a {@code Method} object that reflects the specified public
* member method of the class or interface represented by this
* {@code Class} object. The {@code name} parameter is a
* {@code String} specifying the simple name of the desired method. The
* {@code parameterTypes} parameter is an array of {@code Class}
* objects that identify the method's formal parameter types, in declared
* order. If {@code parameterTypes} is {@code null}, it is
* treated as if it were an empty array.
*
* <p> If the {@code name} is "{@code <init>}" or "{@code <clinit>}" a
* {@code NoSuchMethodException} is raised. Otherwise, the method to
* be reflected is determined by the algorithm that follows. Let C be the
* class or interface represented by this object:
* <OL>
* <LI> C is searched for a <I>matching method</I>, as defined below. If a
* matching method is found, it is reflected.</LI>
* <LI> If no matching method is found by step 1 then:
* <OL TYPE="a">
* <LI> If C is a class other than {@code Object}, then this algorithm is
* invoked recursively on the superclass of C.</LI>
* <LI> If C is the class {@code Object}, or if C is an interface, then
* the superinterfaces of C (if any) are searched for a matching
* method. If any such method is found, it is reflected.</LI>
* </OL></LI>
* </OL>
*
* <p> To find a matching method in a class or interface C: If C
* declares exactly one public method with the specified name and exactly
* the same formal parameter types, that is the method reflected. If more
* than one such method is found in C, and one of these methods has a
* return type that is more specific than any of the others, that method is
* reflected; otherwise one of the methods is chosen arbitrarily.
*
* <p>Note that there may be more than one matching method in a
* class because while the Java language forbids a class to
* declare multiple methods with the same signature but different
* return types, the Java virtual machine does not. This
* increased flexibility in the virtual machine can be used to
* implement various language features. For example, covariant
* returns can be implemented with {@linkplain
* java.lang.reflect.Method#isBridge bridge methods}; the bridge
* method and the method being overridden would have the same
* signature but different return types.
*
* <p> If this {@code Class} object represents an array type, then this
* method does not find the {@code clone()} method.
*
* <p> Static methods declared in superinterfaces of the class or interface
* represented by this {@code Class} object are not considered members of
* the class or interface.
*
* @param name the name of the method
* @param parameterTypes the list of parameters
* @return the {@code Method} object that matches the specified
* {@code name} and {@code parameterTypes}
* @throws NoSuchMethodException if a matching method is not found
* or if the name is "<init>"or "<clinit>".
* @throws NullPointerException if {@code name} is {@code null}
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since JDK1.1
*/
@CallerSensitive
public Method getMethod(String name, Class<?>... parameterTypes)
throws NoSuchMethodException, SecurityException {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);
Method method = getMethod0(name, parameterTypes, true);
if (method == null) {
throw new NoSuchMethodException(getName() + "." + name + argumentTypesToString(parameterTypes));
}
return method;
} /**
* Returns a {@code Constructor} object that reflects the specified
* public constructor of the class represented by this {@code Class}
* object. The {@code parameterTypes} parameter is an array of
* {@code Class} objects that identify the constructor's formal
* parameter types, in declared order.
*
* If this {@code Class} object represents an inner class
* declared in a non-static context, the formal parameter types
* include the explicit enclosing instance as the first parameter.
*
* <p> The constructor to reflect is the public constructor of the class
* represented by this {@code Class} object whose formal parameter
* types match those specified by {@code parameterTypes}.
*
* @param parameterTypes the parameter array
* @return the {@code Constructor} object of the public constructor that
* matches the specified {@code parameterTypes}
* @throws NoSuchMethodException if a matching method is not found.
* @throws SecurityException
* If a security manager, <i>s</i>, is present and
* the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class.
*
* @since JDK1.1
*/
@CallerSensitive
public Constructor<T> getConstructor(Class<?>... parameterTypes)
throws NoSuchMethodException, SecurityException {
checkMemberAccess(Member.PUBLIC, Reflection.getCallerClass(), true);
return getConstructor0(parameterTypes, Member.PUBLIC);
} /**
* Returns an array of {@code Class} objects reflecting all the
* classes and interfaces declared as members of the class represented by
* this {@code Class} object. This includes public, protected, default
* (package) access, and private classes and interfaces declared by the
* class, but excludes inherited classes and interfaces. This method
* returns an array of length 0 if the class declares no classes or
* interfaces as members, or if this {@code Class} object represents a
* primitive type, an array class, or void.
*
* @return the array of {@code Class} objects representing all the
* declared members of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared classes within this class
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @since JDK1.1
*/
@CallerSensitive
public Class<?>[] getDeclaredClasses() throws SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), false);
return getDeclaredClasses0();
} /**
* Returns an array of {@code Field} objects reflecting all the fields
* declared by the class or interface represented by this
* {@code Class} object. This includes public, protected, default
* (package) access, and private fields, but excludes inherited fields.
*
* <p> If this {@code Class} object represents a class or interface with no
* declared fields, then this method returns an array of length 0.
*
* <p> If this {@code Class} object represents an array type, a primitive
* type, or void, then this method returns an array of length 0.
*
* <p> The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Field} objects representing all the
* declared fields of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared fields within this class
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @since JDK1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
@CallerSensitive
public Field[] getDeclaredFields() throws SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);
return copyFields(privateGetDeclaredFields(false));
} /**
*
* Returns an array containing {@code Method} objects reflecting all the
* declared methods of the class or interface represented by this {@code
* Class} object, including public, protected, default (package)
* access, and private methods, but excluding inherited methods.
*
* <p> If this {@code Class} object represents a type that has multiple
* declared methods with the same name and parameter types, but different
* return types, then the returned array has a {@code Method} object for
* each such method.
*
* <p> If this {@code Class} object represents a type that has a class
* initialization method {@code <clinit>}, then the returned array does
* <em>not</em> have a corresponding {@code Method} object.
*
* <p> If this {@code Class} object represents a class or interface with no
* declared methods, then the returned array has length 0.
*
* <p> If this {@code Class} object represents an array type, a primitive
* type, or void, then the returned array has length 0.
*
* <p> The elements in the returned array are not sorted and are not in any
* particular order.
*
* @return the array of {@code Method} objects representing all the
* declared methods of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared methods within this class
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since JDK1.1
*/
@CallerSensitive
public Method[] getDeclaredMethods() throws SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);
return copyMethods(privateGetDeclaredMethods(false));
} /**
* Returns an array of {@code Constructor} objects reflecting all the
* constructors declared by the class represented by this
* {@code Class} object. These are public, protected, default
* (package) access, and private constructors. The elements in the array
* returned are not sorted and are not in any particular order. If the
* class has a default constructor, it is included in the returned array.
* This method returns an array of length 0 if this {@code Class}
* object represents an interface, a primitive type, an array class, or
* void.
*
* <p> See <em>The Java Language Specification</em>, section 8.2.
*
* @return the array of {@code Constructor} objects representing all the
* declared constructors of this class
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared constructors within this class
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @since JDK1.1
*/
@CallerSensitive
public Constructor<?>[] getDeclaredConstructors() throws SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);
return copyConstructors(privateGetDeclaredConstructors(false));
} /**
* Returns a {@code Field} object that reflects the specified declared
* field of the class or interface represented by this {@code Class}
* object. The {@code name} parameter is a {@code String} that specifies
* the simple name of the desired field.
*
* <p> If this {@code Class} object represents an array type, then this
* method does not find the {@code length} field of the array type.
*
* @param name the name of the field
* @return the {@code Field} object for the specified field in this
* class
* @throws NoSuchFieldException if a field with the specified name is
* not found.
* @throws NullPointerException if {@code name} is {@code null}
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared field
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @since JDK1.1
* @jls 8.2 Class Members
* @jls 8.3 Field Declarations
*/
@CallerSensitive
public Field getDeclaredField(String name)
throws NoSuchFieldException, SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);
Field field = searchFields(privateGetDeclaredFields(false), name);
if (field == null) {
throw new NoSuchFieldException(name);
}
return field;
} /**
* Returns a {@code Method} object that reflects the specified
* declared method of the class or interface represented by this
* {@code Class} object. The {@code name} parameter is a
* {@code String} that specifies the simple name of the desired
* method, and the {@code parameterTypes} parameter is an array of
* {@code Class} objects that identify the method's formal parameter
* types, in declared order. If more than one method with the same
* parameter types is declared in a class, and one of these methods has a
* return type that is more specific than any of the others, that method is
* returned; otherwise one of the methods is chosen arbitrarily. If the
* name is "<init>"or "<clinit>" a {@code NoSuchMethodException}
* is raised.
*
* <p> If this {@code Class} object represents an array type, then this
* method does not find the {@code clone()} method.
*
* @param name the name of the method
* @param parameterTypes the parameter array
* @return the {@code Method} object for the method of this class
* matching the specified name and parameters
* @throws NoSuchMethodException if a matching method is not found.
* @throws NullPointerException if {@code name} is {@code null}
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared method
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @jls 8.2 Class Members
* @jls 8.4 Method Declarations
* @since JDK1.1
*/
@CallerSensitive
public Method getDeclaredMethod(String name, Class<?>... parameterTypes)
throws NoSuchMethodException, SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);
Method method = searchMethods(privateGetDeclaredMethods(false), name, parameterTypes);
if (method == null) {
throw new NoSuchMethodException(getName() + "." + name + argumentTypesToString(parameterTypes));
}
return method;
} /**
* Returns a {@code Constructor} object that reflects the specified
* constructor of the class or interface represented by this
* {@code Class} object. The {@code parameterTypes} parameter is
* an array of {@code Class} objects that identify the constructor's
* formal parameter types, in declared order.
*
* If this {@code Class} object represents an inner class
* declared in a non-static context, the formal parameter types
* include the explicit enclosing instance as the first parameter.
*
* @param parameterTypes the parameter array
* @return The {@code Constructor} object for the constructor with the
* specified parameter list
* @throws NoSuchMethodException if a matching method is not found.
* @throws SecurityException
* If a security manager, <i>s</i>, is present and any of the
* following conditions is met:
*
* <ul>
*
* <li> the caller's class loader is not the same as the
* class loader of this class and invocation of
* {@link SecurityManager#checkPermission
* s.checkPermission} method with
* {@code RuntimePermission("accessDeclaredMembers")}
* denies access to the declared constructor
*
* <li> the caller's class loader is not the same as or an
* ancestor of the class loader for the current class and
* invocation of {@link SecurityManager#checkPackageAccess
* s.checkPackageAccess()} denies access to the package
* of this class
*
* </ul>
*
* @since JDK1.1
*/
@CallerSensitive
public Constructor<T> getDeclaredConstructor(Class<?>... parameterTypes)
throws NoSuchMethodException, SecurityException {
checkMemberAccess(Member.DECLARED, Reflection.getCallerClass(), true);
return getConstructor0(parameterTypes, Member.DECLARED);
} /**
* Finds a resource with a given name. The rules for searching resources
* associated with a given class are implemented by the defining
* {@linkplain ClassLoader class loader} of the class. This method
* delegates to this object's class loader. If this object was loaded by
* the bootstrap class loader, the method delegates to {@link
* ClassLoader#getSystemResourceAsStream}.
*
* <p> Before delegation, an absolute resource name is constructed from the
* given resource name using this algorithm:
*
* <ul>
*
* <li> If the {@code name} begins with a {@code '/'}
* (<tt>'\u002f'</tt>), then the absolute name of the resource is the
* portion of the {@code name} following the {@code '/'}.
*
* <li> Otherwise, the absolute name is of the following form:
*
* <blockquote>
* {@code modified_package_name/name}
* </blockquote>
*
* <p> Where the {@code modified_package_name} is the package name of this
* object with {@code '/'} substituted for {@code '.'}
* (<tt>'\u002e'</tt>).
*
* </ul>
*
* @param name name of the desired resource
* @return A {@link java.io.InputStream} object or {@code null} if
* no resource with this name is found
* @throws NullPointerException If {@code name} is {@code null}
* @since JDK1.1
*/
public InputStream getResourceAsStream(String name) {
name = resolveName(name);
ClassLoader cl = getClassLoader0();
if (cl==null) {
// A system class.
return ClassLoader.getSystemResourceAsStream(name);
}
return cl.getResourceAsStream(name);
} /**
* Finds a resource with a given name. The rules for searching resources
* associated with a given class are implemented by the defining
* {@linkplain ClassLoader class loader} of the class. This method
* delegates to this object's class loader. If this object was loaded by
* the bootstrap class loader, the method delegates to {@link
* ClassLoader#getSystemResource}.
*
* <p> Before delegation, an absolute resource name is constructed from the
* given resource name using this algorithm:
*
* <ul>
*
* <li> If the {@code name} begins with a {@code '/'}
* (<tt>'\u002f'</tt>), then the absolute name of the resource is the
* portion of the {@code name} following the {@code '/'}.
*
* <li> Otherwise, the absolute name is of the following form:
*
* <blockquote>
* {@code modified_package_name/name}
* </blockquote>
*
* <p> Where the {@code modified_package_name} is the package name of this
* object with {@code '/'} substituted for {@code '.'}
* (<tt>'\u002e'</tt>).
*
* </ul>
*
* @param name name of the desired resource
* @return A {@link java.net.URL} object or {@code null} if no
* resource with this name is found
* @since JDK1.1
*/
public java.net.URL getResource(String name) {
name = resolveName(name);
ClassLoader cl = getClassLoader0();
if (cl==null) {
// A system class.
return ClassLoader.getSystemResource(name);
}
return cl.getResource(name);
} /** protection domain returned when the internal domain is null */
private static java.security.ProtectionDomain allPermDomain; /**
* Returns the {@code ProtectionDomain} of this class. If there is a
* security manager installed, this method first calls the security
* manager's {@code checkPermission} method with a
* {@code RuntimePermission("getProtectionDomain")} permission to
* ensure it's ok to get the
* {@code ProtectionDomain}.
*
* @return the ProtectionDomain of this class
*
* @throws SecurityException
* if a security manager exists and its
* {@code checkPermission} method doesn't allow
* getting the ProtectionDomain.
*
* @see java.security.ProtectionDomain
* @see SecurityManager#checkPermission
* @see java.lang.RuntimePermission
* @since 1.2
*/
public java.security.ProtectionDomain getProtectionDomain() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(SecurityConstants.GET_PD_PERMISSION);
}
java.security.ProtectionDomain pd = getProtectionDomain0();
if (pd == null) {
if (allPermDomain == null) {
java.security.Permissions perms =
new java.security.Permissions();
perms.add(SecurityConstants.ALL_PERMISSION);
allPermDomain =
new java.security.ProtectionDomain(null, perms);
}
pd = allPermDomain;
}
return pd;
} /**
* Returns the ProtectionDomain of this class.
*/
private native java.security.ProtectionDomain getProtectionDomain0(); /*
* Return the Virtual Machine's Class object for the named
* primitive type.
*/
static native Class<?> getPrimitiveClass(String name); /*
* Check if client is allowed to access members. If access is denied,
* throw a SecurityException.
*
* This method also enforces package access.
*
* <p> Default policy: allow all clients access with normal Java access
* control.
*/
private void checkMemberAccess(int which, Class<?> caller, boolean checkProxyInterfaces) {
final SecurityManager s = System.getSecurityManager();
if (s != null) {
/* Default policy allows access to all {@link Member#PUBLIC} members,
* as well as access to classes that have the same class loader as the caller.
* In all other cases, it requires RuntimePermission("accessDeclaredMembers")
* permission.
*/
final ClassLoader ccl = ClassLoader.getClassLoader(caller);
final ClassLoader cl = getClassLoader0();
if (which != Member.PUBLIC) {
if (ccl != cl) {
s.checkPermission(SecurityConstants.CHECK_MEMBER_ACCESS_PERMISSION);
}
}
this.checkPackageAccess(ccl, checkProxyInterfaces);
}
} /*
* Checks if a client loaded in ClassLoader ccl is allowed to access this
* class under the current package access policy. If access is denied,
* throw a SecurityException.
*/
private void checkPackageAccess(final ClassLoader ccl, boolean checkProxyInterfaces) {
final SecurityManager s = System.getSecurityManager();
if (s != null) {
final ClassLoader cl = getClassLoader0(); if (ReflectUtil.needsPackageAccessCheck(ccl, cl)) {
String name = this.getName();
int i = name.lastIndexOf('.');
if (i != -1) {
// skip the package access check on a proxy class in default proxy package
String pkg = name.substring(0, i);
if (!Proxy.isProxyClass(this) || ReflectUtil.isNonPublicProxyClass(this)) {
s.checkPackageAccess(pkg);
}
}
}
// check package access on the proxy interfaces
if (checkProxyInterfaces && Proxy.isProxyClass(this)) {
ReflectUtil.checkProxyPackageAccess(ccl, this.getInterfaces());
}
}
} /**
* Add a package name prefix if the name is not absolute Remove leading "/"
* if name is absolute
*/
private String resolveName(String name) {
if (name == null) {
return name;
}
if (!name.startsWith("/")) {
Class<?> c = this;
while (c.isArray()) {
c = c.getComponentType();
}
String baseName = c.getName();
int index = baseName.lastIndexOf('.');
if (index != -1) {
name = baseName.substring(0, index).replace('.', '/')
+"/"+name;
}
} else {
name = name.substring(1);
}
return name;
} /**
* Atomic operations support.
*/
private static class Atomic {
// initialize Unsafe machinery here, since we need to call Class.class instance method
// and have to avoid calling it in the static initializer of the Class class...
private static final Unsafe unsafe = Unsafe.getUnsafe();
// offset of Class.reflectionData instance field
private static final long reflectionDataOffset;
// offset of Class.annotationType instance field
private static final long annotationTypeOffset;
// offset of Class.annotationData instance field
private static final long annotationDataOffset; static {
Field[] fields = Class.class.getDeclaredFields0(false); // bypass caches
reflectionDataOffset = objectFieldOffset(fields, "reflectionData");
annotationTypeOffset = objectFieldOffset(fields, "annotationType");
annotationDataOffset = objectFieldOffset(fields, "annotationData");
} private static long objectFieldOffset(Field[] fields, String fieldName) {
Field field = searchFields(fields, fieldName);
if (field == null) {
throw new Error("No " + fieldName + " field found in java.lang.Class");
}
return unsafe.objectFieldOffset(field);
} static <T> boolean casReflectionData(Class<?> clazz,
SoftReference<ReflectionData<T>> oldData,
SoftReference<ReflectionData<T>> newData) {
return unsafe.compareAndSwapObject(clazz, reflectionDataOffset, oldData, newData);
} static <T> boolean casAnnotationType(Class<?> clazz,
AnnotationType oldType,
AnnotationType newType) {
return unsafe.compareAndSwapObject(clazz, annotationTypeOffset, oldType, newType);
} static <T> boolean casAnnotationData(Class<?> clazz,
AnnotationData oldData,
AnnotationData newData) {
return unsafe.compareAndSwapObject(clazz, annotationDataOffset, oldData, newData);
}
} /**
* Reflection support.
*/ // Caches for certain reflective results
private static boolean useCaches = true; // reflection data that might get invalidated when JVM TI RedefineClasses() is called
private static class ReflectionData<T> {
volatile Field[] declaredFields;
volatile Field[] publicFields;
volatile Method[] declaredMethods;
volatile Method[] publicMethods;
volatile Constructor<T>[] declaredConstructors;
volatile Constructor<T>[] publicConstructors;
// Intermediate results for getFields and getMethods
volatile Field[] declaredPublicFields;
volatile Method[] declaredPublicMethods;
volatile Class<?>[] interfaces; // Value of classRedefinedCount when we created this ReflectionData instance
final int redefinedCount; ReflectionData(int redefinedCount) {
this.redefinedCount = redefinedCount;
}
} private volatile transient SoftReference<ReflectionData<T>> reflectionData; // Incremented by the VM on each call to JVM TI RedefineClasses()
// that redefines this class or a superclass.
private volatile transient int classRedefinedCount = 0; // Lazily create and cache ReflectionData
private ReflectionData<T> reflectionData() {
SoftReference<ReflectionData<T>> reflectionData = this.reflectionData;
int classRedefinedCount = this.classRedefinedCount;
ReflectionData<T> rd;
if (useCaches &&
reflectionData != null &&
(rd = reflectionData.get()) != null &&
rd.redefinedCount == classRedefinedCount) {
return rd;
}
// else no SoftReference or cleared SoftReference or stale ReflectionData
// -> create and replace new instance
return newReflectionData(reflectionData, classRedefinedCount);
} private ReflectionData<T> newReflectionData(SoftReference<ReflectionData<T>> oldReflectionData,
int classRedefinedCount) {
if (!useCaches) return null; while (true) {
ReflectionData<T> rd = new ReflectionData<>(classRedefinedCount);
// try to CAS it...
if (Atomic.casReflectionData(this, oldReflectionData, new SoftReference<>(rd))) {
return rd;
}
// else retry
oldReflectionData = this.reflectionData;
classRedefinedCount = this.classRedefinedCount;
if (oldReflectionData != null &&
(rd = oldReflectionData.get()) != null &&
rd.redefinedCount == classRedefinedCount) {
return rd;
}
}
} // Generic signature handling
private native String getGenericSignature0(); // Generic info repository; lazily initialized
private volatile transient ClassRepository genericInfo; // accessor for factory
private GenericsFactory getFactory() {
// create scope and factory
return CoreReflectionFactory.make(this, ClassScope.make(this));
} // accessor for generic info repository;
// generic info is lazily initialized
private ClassRepository getGenericInfo() {
ClassRepository genericInfo = this.genericInfo;
if (genericInfo == null) {
String signature = getGenericSignature0();
if (signature == null) {
genericInfo = ClassRepository.NONE;
} else {
genericInfo = ClassRepository.make(signature, getFactory());
}
this.genericInfo = genericInfo;
}
return (genericInfo != ClassRepository.NONE) ? genericInfo : null;
} // Annotations handling
native byte[] getRawAnnotations();
// Since 1.8
native byte[] getRawTypeAnnotations();
static byte[] getExecutableTypeAnnotationBytes(Executable ex) {
return getReflectionFactory().getExecutableTypeAnnotationBytes(ex);
} native ConstantPool getConstantPool(); //
//
// java.lang.reflect.Field handling
//
// // Returns an array of "root" fields. These Field objects must NOT
// be propagated to the outside world, but must instead be copied
// via ReflectionFactory.copyField.
private Field[] privateGetDeclaredFields(boolean publicOnly) {
checkInitted();
Field[] res;
ReflectionData<T> rd = reflectionData();
if (rd != null) {
res = publicOnly ? rd.declaredPublicFields : rd.declaredFields;
if (res != null) return res;
}
// No cached value available; request value from VM
res = Reflection.filterFields(this, getDeclaredFields0(publicOnly));
if (rd != null) {
if (publicOnly) {
rd.declaredPublicFields = res;
} else {
rd.declaredFields = res;
}
}
return res;
} // Returns an array of "root" fields. These Field objects must NOT
// be propagated to the outside world, but must instead be copied
// via ReflectionFactory.copyField.
private Field[] privateGetPublicFields(Set<Class<?>> traversedInterfaces) {
checkInitted();
Field[] res;
ReflectionData<T> rd = reflectionData();
if (rd != null) {
res = rd.publicFields;
if (res != null) return res;
} // No cached value available; compute value recursively.
// Traverse in correct order for getField().
List<Field> fields = new ArrayList<>();
if (traversedInterfaces == null) {
traversedInterfaces = new HashSet<>();
} // Local fields
Field[] tmp = privateGetDeclaredFields(true);
addAll(fields, tmp); // Direct superinterfaces, recursively
for (Class<?> c : getInterfaces()) {
if (!traversedInterfaces.contains(c)) {
traversedInterfaces.add(c);
addAll(fields, c.privateGetPublicFields(traversedInterfaces));
}
} // Direct superclass, recursively
if (!isInterface()) {
Class<?> c = getSuperclass();
if (c != null) {
addAll(fields, c.privateGetPublicFields(traversedInterfaces));
}
} res = new Field[fields.size()];
fields.toArray(res);
if (rd != null) {
rd.publicFields = res;
}
return res;
} private static void addAll(Collection<Field> c, Field[] o) {
for (int i = 0; i < o.length; i++) {
c.add(o[i]);
}
} //
//
// java.lang.reflect.Constructor handling
//
// // Returns an array of "root" constructors. These Constructor
// objects must NOT be propagated to the outside world, but must
// instead be copied via ReflectionFactory.copyConstructor.
private Constructor<T>[] privateGetDeclaredConstructors(boolean publicOnly) {
checkInitted();
Constructor<T>[] res;
ReflectionData<T> rd = reflectionData();
if (rd != null) {
res = publicOnly ? rd.publicConstructors : rd.declaredConstructors;
if (res != null) return res;
}
// No cached value available; request value from VM
if (isInterface()) {
@SuppressWarnings("unchecked")
Constructor<T>[] temporaryRes = (Constructor<T>[]) new Constructor<?>[0];
res = temporaryRes;
} else {
res = getDeclaredConstructors0(publicOnly);
}
if (rd != null) {
if (publicOnly) {
rd.publicConstructors = res;
} else {
rd.declaredConstructors = res;
}
}
return res;
} //
//
// java.lang.reflect.Method handling
//
// // Returns an array of "root" methods. These Method objects must NOT
// be propagated to the outside world, but must instead be copied
// via ReflectionFactory.copyMethod.
private Method[] privateGetDeclaredMethods(boolean publicOnly) {
checkInitted();
Method[] res;
ReflectionData<T> rd = reflectionData();
if (rd != null) {
res = publicOnly ? rd.declaredPublicMethods : rd.declaredMethods;
if (res != null) return res;
}
// No cached value available; request value from VM
res = Reflection.filterMethods(this, getDeclaredMethods0(publicOnly));
if (rd != null) {
if (publicOnly) {
rd.declaredPublicMethods = res;
} else {
rd.declaredMethods = res;
}
}
return res;
} static class MethodArray {
// Don't add or remove methods except by add() or remove() calls.
private Method[] methods;
private int length;
private int defaults; MethodArray() {
this(20);
} MethodArray(int initialSize) {
if (initialSize < 2)
throw new IllegalArgumentException("Size should be 2 or more"); methods = new Method[initialSize];
length = 0;
defaults = 0;
} boolean hasDefaults() {
return defaults != 0;
} void add(Method m) {
if (length == methods.length) {
methods = Arrays.copyOf(methods, 2 * methods.length);
}
methods[length++] = m; if (m != null && m.isDefault())
defaults++;
} void addAll(Method[] ma) {
for (int i = 0; i < ma.length; i++) {
add(ma[i]);
}
} void addAll(MethodArray ma) {
for (int i = 0; i < ma.length(); i++) {
add(ma.get(i));
}
} void addIfNotPresent(Method newMethod) {
for (int i = 0; i < length; i++) {
Method m = methods[i];
if (m == newMethod || (m != null && m.equals(newMethod))) {
return;
}
}
add(newMethod);
} void addAllIfNotPresent(MethodArray newMethods) {
for (int i = 0; i < newMethods.length(); i++) {
Method m = newMethods.get(i);
if (m != null) {
addIfNotPresent(m);
}
}
} /* Add Methods declared in an interface to this MethodArray.
* Static methods declared in interfaces are not inherited.
*/
void addInterfaceMethods(Method[] methods) {
for (Method candidate : methods) {
if (!Modifier.isStatic(candidate.getModifiers())) {
add(candidate);
}
}
} int length() {
return length;
} Method get(int i) {
return methods[i];
} Method getFirst() {
for (Method m : methods)
if (m != null)
return m;
return null;
} void removeByNameAndDescriptor(Method toRemove) {
for (int i = 0; i < length; i++) {
Method m = methods[i];
if (m != null && matchesNameAndDescriptor(m, toRemove)) {
remove(i);
}
}
} private void remove(int i) {
if (methods[i] != null && methods[i].isDefault())
defaults--;
methods[i] = null;
} private boolean matchesNameAndDescriptor(Method m1, Method m2) {
return m1.getReturnType() == m2.getReturnType() &&
m1.getName() == m2.getName() && // name is guaranteed to be interned
arrayContentsEq(m1.getParameterTypes(),
m2.getParameterTypes());
} void compactAndTrim() {
int newPos = 0;
// Get rid of null slots
for (int pos = 0; pos < length; pos++) {
Method m = methods[pos];
if (m != null) {
if (pos != newPos) {
methods[newPos] = m;
}
newPos++;
}
}
if (newPos != methods.length) {
methods = Arrays.copyOf(methods, newPos);
}
} /* Removes all Methods from this MethodArray that have a more specific
* default Method in this MethodArray.
*
* Users of MethodArray are responsible for pruning Methods that have
* a more specific <em>concrete</em> Method.
*/
void removeLessSpecifics() {
if (!hasDefaults())
return; for (int i = 0; i < length; i++) {
Method m = get(i);
if (m == null || !m.isDefault())
continue; for (int j = 0; j < length; j++) {
if (i == j)
continue; Method candidate = get(j);
if (candidate == null)
continue; if (!matchesNameAndDescriptor(m, candidate))
continue; if (hasMoreSpecificClass(m, candidate))
remove(j);
}
}
} Method[] getArray() {
return methods;
} // Returns true if m1 is more specific than m2
static boolean hasMoreSpecificClass(Method m1, Method m2) {
Class<?> m1Class = m1.getDeclaringClass();
Class<?> m2Class = m2.getDeclaringClass();
return m1Class != m2Class && m2Class.isAssignableFrom(m1Class);
}
} // Returns an array of "root" methods. These Method objects must NOT
// be propagated to the outside world, but must instead be copied
// via ReflectionFactory.copyMethod.
private Method[] privateGetPublicMethods() {
checkInitted();
Method[] res;
ReflectionData<T> rd = reflectionData();
if (rd != null) {
res = rd.publicMethods;
if (res != null) return res;
} // No cached value available; compute value recursively.
// Start by fetching public declared methods
MethodArray methods = new MethodArray();
{
Method[] tmp = privateGetDeclaredMethods(true);
methods.addAll(tmp);
}
// Now recur over superclass and direct superinterfaces.
// Go over superinterfaces first so we can more easily filter
// out concrete implementations inherited from superclasses at
// the end.
MethodArray inheritedMethods = new MethodArray();
for (Class<?> i : getInterfaces()) {
inheritedMethods.addInterfaceMethods(i.privateGetPublicMethods());
}
if (!isInterface()) {
Class<?> c = getSuperclass();
if (c != null) {
MethodArray supers = new MethodArray();
supers.addAll(c.privateGetPublicMethods());
// Filter out concrete implementations of any
// interface methods
for (int i = 0; i < supers.length(); i++) {
Method m = supers.get(i);
if (m != null &&
!Modifier.isAbstract(m.getModifiers()) &&
!m.isDefault()) {
inheritedMethods.removeByNameAndDescriptor(m);
}
}
// Insert superclass's inherited methods before
// superinterfaces' to satisfy getMethod's search
// order
supers.addAll(inheritedMethods);
inheritedMethods = supers;
}
}
// Filter out all local methods from inherited ones
for (int i = 0; i < methods.length(); i++) {
Method m = methods.get(i);
inheritedMethods.removeByNameAndDescriptor(m);
}
methods.addAllIfNotPresent(inheritedMethods);
methods.removeLessSpecifics();
methods.compactAndTrim();
res = methods.getArray();
if (rd != null) {
rd.publicMethods = res;
}
return res;
} //
// Helpers for fetchers of one field, method, or constructor
// private static Field searchFields(Field[] fields, String name) {
String internedName = name.intern();
for (int i = 0; i < fields.length; i++) {
if (fields[i].getName() == internedName) {
return getReflectionFactory().copyField(fields[i]);
}
}
return null;
} private Field getField0(String name) throws NoSuchFieldException {
// Note: the intent is that the search algorithm this routine
// uses be equivalent to the ordering imposed by
// privateGetPublicFields(). It fetches only the declared
// public fields for each class, however, to reduce the number
// of Field objects which have to be created for the common
// case where the field being requested is declared in the
// class which is being queried.
Field res;
// Search declared public fields
if ((res = searchFields(privateGetDeclaredFields(true), name)) != null) {
return res;
}
// Direct superinterfaces, recursively
Class<?>[] interfaces = getInterfaces();
for (int i = 0; i < interfaces.length; i++) {
Class<?> c = interfaces[i];
if ((res = c.getField0(name)) != null) {
return res;
}
}
// Direct superclass, recursively
if (!isInterface()) {
Class<?> c = getSuperclass();
if (c != null) {
if ((res = c.getField0(name)) != null) {
return res;
}
}
}
return null;
} private static Method searchMethods(Method[] methods,
String name,
Class<?>[] parameterTypes)
{
Method res = null;
String internedName = name.intern();
for (int i = 0; i < methods.length; i++) {
Method m = methods[i];
if (m.getName() == internedName
&& arrayContentsEq(parameterTypes, m.getParameterTypes())
&& (res == null
|| res.getReturnType().isAssignableFrom(m.getReturnType())))
res = m;
} return (res == null ? res : getReflectionFactory().copyMethod(res));
} private Method getMethod0(String name, Class<?>[] parameterTypes, boolean includeStaticMethods) {
MethodArray interfaceCandidates = new MethodArray(2);
Method res = privateGetMethodRecursive(name, parameterTypes, includeStaticMethods, interfaceCandidates);
if (res != null)
return res; // Not found on class or superclass directly
interfaceCandidates.removeLessSpecifics();
return interfaceCandidates.getFirst(); // may be null
} private Method privateGetMethodRecursive(String name,
Class<?>[] parameterTypes,
boolean includeStaticMethods,
MethodArray allInterfaceCandidates) {
// Note: the intent is that the search algorithm this routine
// uses be equivalent to the ordering imposed by
// privateGetPublicMethods(). It fetches only the declared
// public methods for each class, however, to reduce the
// number of Method objects which have to be created for the
// common case where the method being requested is declared in
// the class which is being queried.
//
// Due to default methods, unless a method is found on a superclass,
// methods declared in any superinterface needs to be considered.
// Collect all candidates declared in superinterfaces in {@code
// allInterfaceCandidates} and select the most specific if no match on
// a superclass is found. // Must _not_ return root methods
Method res;
// Search declared public methods
if ((res = searchMethods(privateGetDeclaredMethods(true),
name,
parameterTypes)) != null) {
if (includeStaticMethods || !Modifier.isStatic(res.getModifiers()))
return res;
}
// Search superclass's methods
if (!isInterface()) {
Class<? super T> c = getSuperclass();
if (c != null) {
if ((res = c.getMethod0(name, parameterTypes, true)) != null) {
return res;
}
}
}
// Search superinterfaces' methods
Class<?>[] interfaces = getInterfaces();
for (Class<?> c : interfaces)
if ((res = c.getMethod0(name, parameterTypes, false)) != null)
allInterfaceCandidates.add(res);
// Not found
return null;
} private Constructor<T> getConstructor0(Class<?>[] parameterTypes,
int which) throws NoSuchMethodException
{
Constructor<T>[] constructors = privateGetDeclaredConstructors((which == Member.PUBLIC));
for (Constructor<T> constructor : constructors) {
if (arrayContentsEq(parameterTypes,
constructor.getParameterTypes())) {
return getReflectionFactory().copyConstructor(constructor);
}
}
throw new NoSuchMethodException(getName() + ".<init>" + argumentTypesToString(parameterTypes));
} //
// Other helpers and base implementation
// private static boolean arrayContentsEq(Object[] a1, Object[] a2) {
if (a1 == null) {
return a2 == null || a2.length == 0;
} if (a2 == null) {
return a1.length == 0;
} if (a1.length != a2.length) {
return false;
} for (int i = 0; i < a1.length; i++) {
if (a1[i] != a2[i]) {
return false;
}
} return true;
} private static Field[] copyFields(Field[] arg) {
Field[] out = new Field[arg.length];
ReflectionFactory fact = getReflectionFactory();
for (int i = 0; i < arg.length; i++) {
out[i] = fact.copyField(arg[i]);
}
return out;
} private static Method[] copyMethods(Method[] arg) {
Method[] out = new Method[arg.length];
ReflectionFactory fact = getReflectionFactory();
for (int i = 0; i < arg.length; i++) {
out[i] = fact.copyMethod(arg[i]);
}
return out;
} private static <U> Constructor<U>[] copyConstructors(Constructor<U>[] arg) {
Constructor<U>[] out = arg.clone();
ReflectionFactory fact = getReflectionFactory();
for (int i = 0; i < out.length; i++) {
out[i] = fact.copyConstructor(out[i]);
}
return out;
} private native Field[] getDeclaredFields0(boolean publicOnly);
private native Method[] getDeclaredMethods0(boolean publicOnly);
private native Constructor<T>[] getDeclaredConstructors0(boolean publicOnly);
private native Class<?>[] getDeclaredClasses0(); private static String argumentTypesToString(Class<?>[] argTypes) {
StringBuilder buf = new StringBuilder();
buf.append("(");
if (argTypes != null) {
for (int i = 0; i < argTypes.length; i++) {
if (i > 0) {
buf.append(", ");
}
Class<?> c = argTypes[i];
buf.append((c == null) ? "null" : c.getName());
}
}
buf.append(")");
return buf.toString();
} /** use serialVersionUID from JDK 1.1 for interoperability */
private static final long serialVersionUID = 3206093459760846163L; /**
* Class Class is special cased within the Serialization Stream Protocol.
*
* A Class instance is written initially into an ObjectOutputStream in the
* following format:
* <pre>
* {@code TC_CLASS} ClassDescriptor
* A ClassDescriptor is a special cased serialization of
* a {@code java.io.ObjectStreamClass} instance.
* </pre>
* A new handle is generated for the initial time the class descriptor
* is written into the stream. Future references to the class descriptor
* are written as references to the initial class descriptor instance.
*
* @see java.io.ObjectStreamClass
*/
private static final ObjectStreamField[] serialPersistentFields =
new ObjectStreamField[0]; /**
* Returns the assertion status that would be assigned to this
* class if it were to be initialized at the time this method is invoked.
* If this class has had its assertion status set, the most recent
* setting will be returned; otherwise, if any package default assertion
* status pertains to this class, the most recent setting for the most
* specific pertinent package default assertion status is returned;
* otherwise, if this class is not a system class (i.e., it has a
* class loader) its class loader's default assertion status is returned;
* otherwise, the system class default assertion status is returned.
* <p>
* Few programmers will have any need for this method; it is provided
* for the benefit of the JRE itself. (It allows a class to determine at
* the time that it is initialized whether assertions should be enabled.)
* Note that this method is not guaranteed to return the actual
* assertion status that was (or will be) associated with the specified
* class when it was (or will be) initialized.
*
* @return the desired assertion status of the specified class.
* @see java.lang.ClassLoader#setClassAssertionStatus
* @see java.lang.ClassLoader#setPackageAssertionStatus
* @see java.lang.ClassLoader#setDefaultAssertionStatus
* @since 1.4
*/
public boolean desiredAssertionStatus() {
ClassLoader loader = getClassLoader();
// If the loader is null this is a system class, so ask the VM
if (loader == null)
return desiredAssertionStatus0(this); // If the classloader has been initialized with the assertion
// directives, ask it. Otherwise, ask the VM.
synchronized(loader.assertionLock) {
if (loader.classAssertionStatus != null) {
return loader.desiredAssertionStatus(getName());
}
}
return desiredAssertionStatus0(this);
} // Retrieves the desired assertion status of this class from the VM
private static native boolean desiredAssertionStatus0(Class<?> clazz); /**
* Returns true if and only if this class was declared as an enum in the
* source code.
*
* @return true if and only if this class was declared as an enum in the
* source code
* @since 1.5
*/
public boolean isEnum() {
// An enum must both directly extend java.lang.Enum and have
// the ENUM bit set; classes for specialized enum constants
// don't do the former.
return (this.getModifiers() & ENUM) != 0 &&
this.getSuperclass() == java.lang.Enum.class;
} // Fetches the factory for reflective objects
private static ReflectionFactory getReflectionFactory() {
if (reflectionFactory == null) {
reflectionFactory =
java.security.AccessController.doPrivileged
(new sun.reflect.ReflectionFactory.GetReflectionFactoryAction());
}
return reflectionFactory;
}
private static ReflectionFactory reflectionFactory; // To be able to query system properties as soon as they're available
private static boolean initted = false;
private static void checkInitted() {
if (initted) return;
AccessController.doPrivileged(new PrivilegedAction<Void>() {
public Void run() {
// Tests to ensure the system properties table is fully
// initialized. This is needed because reflection code is
// called very early in the initialization process (before
// command-line arguments have been parsed and therefore
// these user-settable properties installed.) We assume that
// if System.out is non-null then the System class has been
// fully initialized and that the bulk of the startup code
// has been run. if (System.out == null) {
// java.lang.System not yet fully initialized
return null;
} // Doesn't use Boolean.getBoolean to avoid class init.
String val =
System.getProperty("sun.reflect.noCaches");
if (val != null && val.equals("true")) {
useCaches = false;
} initted = true;
return null;
}
});
} /**
* Returns the elements of this enum class or null if this
* Class object does not represent an enum type.
*
* @return an array containing the values comprising the enum class
* represented by this Class object in the order they're
* declared, or null if this Class object does not
* represent an enum type
* @since 1.5
*/
public T[] getEnumConstants() {
T[] values = getEnumConstantsShared();
return (values != null) ? values.clone() : null;
} /**
* Returns the elements of this enum class or null if this
* Class object does not represent an enum type;
* identical to getEnumConstants except that the result is
* uncloned, cached, and shared by all callers.
*/
T[] getEnumConstantsShared() {
if (enumConstants == null) {
if (!isEnum()) return null;
try {
final Method values = getMethod("values");
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction<Void>() {
public Void run() {
values.setAccessible(true);
return null;
}
});
@SuppressWarnings("unchecked")
T[] temporaryConstants = (T[])values.invoke(null);
enumConstants = temporaryConstants;
}
// These can happen when users concoct enum-like classes
// that don't comply with the enum spec.
catch (InvocationTargetException | NoSuchMethodException |
IllegalAccessException ex) { return null; }
}
return enumConstants;
}
private volatile transient T[] enumConstants = null; /**
* Returns a map from simple name to enum constant. This package-private
* method is used internally by Enum to implement
* {@code public static <T extends Enum<T>> T valueOf(Class<T>, String)}
* efficiently. Note that the map is returned by this method is
* created lazily on first use. Typically it won't ever get created.
*/
Map<String, T> enumConstantDirectory() {
if (enumConstantDirectory == null) {
T[] universe = getEnumConstantsShared();
if (universe == null)
throw new IllegalArgumentException(
getName() + " is not an enum type");
Map<String, T> m = new HashMap<>(2 * universe.length);
for (T constant : universe)
m.put(((Enum<?>)constant).name(), constant);
enumConstantDirectory = m;
}
return enumConstantDirectory;
}
private volatile transient Map<String, T> enumConstantDirectory = null; /**
* Casts an object to the class or interface represented
* by this {@code Class} object.
*
* @param obj the object to be cast
* @return the object after casting, or null if obj is null
*
* @throws ClassCastException if the object is not
* null and is not assignable to the type T.
*
* @since 1.5
*/
@SuppressWarnings("unchecked")
public T cast(Object obj) {
if (obj != null && !isInstance(obj))
throw new ClassCastException(cannotCastMsg(obj));
return (T) obj;
} private String cannotCastMsg(Object obj) {
return "Cannot cast " + obj.getClass().getName() + " to " + getName();
} /**
* Casts this {@code Class} object to represent a subclass of the class
* represented by the specified class object. Checks that the cast
* is valid, and throws a {@code ClassCastException} if it is not. If
* this method succeeds, it always returns a reference to this class object.
*
* <p>This method is useful when a client needs to "narrow" the type of
* a {@code Class} object to pass it to an API that restricts the
* {@code Class} objects that it is willing to accept. A cast would
* generate a compile-time warning, as the correctness of the cast
* could not be checked at runtime (because generic types are implemented
* by erasure).
*
* @param <U> the type to cast this class object to
* @param clazz the class of the type to cast this class object to
* @return this {@code Class} object, cast to represent a subclass of
* the specified class object.
* @throws ClassCastException if this {@code Class} object does not
* represent a subclass of the specified class (here "subclass" includes
* the class itself).
* @since 1.5
*/
@SuppressWarnings("unchecked")
public <U> Class<? extends U> asSubclass(Class<U> clazz) {
if (clazz.isAssignableFrom(this))
return (Class<? extends U>) this;
else
throw new ClassCastException(this.toString());
} /**
* @throws NullPointerException {@inheritDoc}
* @since 1.5
*/
@SuppressWarnings("unchecked")
public <A extends Annotation> A getAnnotation(Class<A> annotationClass) {
Objects.requireNonNull(annotationClass); return (A) annotationData().annotations.get(annotationClass);
} /**
* {@inheritDoc}
* @throws NullPointerException {@inheritDoc}
* @since 1.5
*/
@Override
public boolean isAnnotationPresent(Class<? extends Annotation> annotationClass) {
return GenericDeclaration.super.isAnnotationPresent(annotationClass);
} /**
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
public <A extends Annotation> A[] getAnnotationsByType(Class<A> annotationClass) {
Objects.requireNonNull(annotationClass); AnnotationData annotationData = annotationData();
return AnnotationSupport.getAssociatedAnnotations(annotationData.declaredAnnotations,
this,
annotationClass);
} /**
* @since 1.5
*/
public Annotation[] getAnnotations() {
return AnnotationParser.toArray(annotationData().annotations);
} /**
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
@SuppressWarnings("unchecked")
public <A extends Annotation> A getDeclaredAnnotation(Class<A> annotationClass) {
Objects.requireNonNull(annotationClass); return (A) annotationData().declaredAnnotations.get(annotationClass);
} /**
* @throws NullPointerException {@inheritDoc}
* @since 1.8
*/
@Override
public <A extends Annotation> A[] getDeclaredAnnotationsByType(Class<A> annotationClass) {
Objects.requireNonNull(annotationClass); return AnnotationSupport.getDirectlyAndIndirectlyPresent(annotationData().declaredAnnotations,
annotationClass);
} /**
* @since 1.5
*/
public Annotation[] getDeclaredAnnotations() {
return AnnotationParser.toArray(annotationData().declaredAnnotations);
} // annotation data that might get invalidated when JVM TI RedefineClasses() is called
private static class AnnotationData {
final Map<Class<? extends Annotation>, Annotation> annotations;
final Map<Class<? extends Annotation>, Annotation> declaredAnnotations; // Value of classRedefinedCount when we created this AnnotationData instance
final int redefinedCount; AnnotationData(Map<Class<? extends Annotation>, Annotation> annotations,
Map<Class<? extends Annotation>, Annotation> declaredAnnotations,
int redefinedCount) {
this.annotations = annotations;
this.declaredAnnotations = declaredAnnotations;
this.redefinedCount = redefinedCount;
}
} // Annotations cache
@SuppressWarnings("UnusedDeclaration")
private volatile transient AnnotationData annotationData; private AnnotationData annotationData() {
while (true) { // retry loop
AnnotationData annotationData = this.annotationData;
int classRedefinedCount = this.classRedefinedCount;
if (annotationData != null &&
annotationData.redefinedCount == classRedefinedCount) {
return annotationData;
}
// null or stale annotationData -> optimistically create new instance
AnnotationData newAnnotationData = createAnnotationData(classRedefinedCount);
// try to install it
if (Atomic.casAnnotationData(this, annotationData, newAnnotationData)) {
// successfully installed new AnnotationData
return newAnnotationData;
}
}
} private AnnotationData createAnnotationData(int classRedefinedCount) {
Map<Class<? extends Annotation>, Annotation> declaredAnnotations =
AnnotationParser.parseAnnotations(getRawAnnotations(), getConstantPool(), this);
Class<?> superClass = getSuperclass();
Map<Class<? extends Annotation>, Annotation> annotations = null;
if (superClass != null) {
Map<Class<? extends Annotation>, Annotation> superAnnotations =
superClass.annotationData().annotations;
for (Map.Entry<Class<? extends Annotation>, Annotation> e : superAnnotations.entrySet()) {
Class<? extends Annotation> annotationClass = e.getKey();
if (AnnotationType.getInstance(annotationClass).isInherited()) {
if (annotations == null) { // lazy construction
annotations = new LinkedHashMap<>((Math.max(
declaredAnnotations.size(),
Math.min(12, declaredAnnotations.size() + superAnnotations.size())
) * 4 + 2) / 3
);
}
annotations.put(annotationClass, e.getValue());
}
}
}
if (annotations == null) {
// no inherited annotations -> share the Map with declaredAnnotations
annotations = declaredAnnotations;
} else {
// at least one inherited annotation -> declared may override inherited
annotations.putAll(declaredAnnotations);
}
return new AnnotationData(annotations, declaredAnnotations, classRedefinedCount);
} // Annotation types cache their internal (AnnotationType) form @SuppressWarnings("UnusedDeclaration")
private volatile transient AnnotationType annotationType; boolean casAnnotationType(AnnotationType oldType, AnnotationType newType) {
return Atomic.casAnnotationType(this, oldType, newType);
} AnnotationType getAnnotationType() {
return annotationType;
} Map<Class<? extends Annotation>, Annotation> getDeclaredAnnotationMap() {
return annotationData().declaredAnnotations;
} /* Backing store of user-defined values pertaining to this class.
* Maintained by the ClassValue class.
*/
transient ClassValue.ClassValueMap classValueMap; /**
* Returns an {@code AnnotatedType} object that represents the use of a
* type to specify the superclass of the entity represented by this {@code
* Class} object. (The <em>use</em> of type Foo to specify the superclass
* in '... extends Foo' is distinct from the <em>declaration</em> of type
* Foo.)
*
* <p> If this {@code Class} object represents a type whose declaration
* does not explicitly indicate an annotated superclass, then the return
* value is an {@code AnnotatedType} object representing an element with no
* annotations.
*
* <p> If this {@code Class} represents either the {@code Object} class, an
* interface type, an array type, a primitive type, or void, the return
* value is {@code null}.
*
* @return an object representing the superclass
* @since 1.8
*/
public AnnotatedType getAnnotatedSuperclass() {
if (this == Object.class ||
isInterface() ||
isArray() ||
isPrimitive() ||
this == Void.TYPE) {
return null;
} return TypeAnnotationParser.buildAnnotatedSuperclass(getRawTypeAnnotations(), getConstantPool(), this);
} /**
* Returns an array of {@code AnnotatedType} objects that represent the use
* of types to specify superinterfaces of the entity represented by this
* {@code Class} object. (The <em>use</em> of type Foo to specify a
* superinterface in '... implements Foo' is distinct from the
* <em>declaration</em> of type Foo.)
*
* <p> If this {@code Class} object represents a class, the return value is
* an array containing objects representing the uses of interface types to
* specify interfaces implemented by the class. The order of the objects in
* the array corresponds to the order of the interface types used in the
* 'implements' clause of the declaration of this {@code Class} object.
*
* <p> If this {@code Class} object represents an interface, the return
* value is an array containing objects representing the uses of interface
* types to specify interfaces directly extended by the interface. The
* order of the objects in the array corresponds to the order of the
* interface types used in the 'extends' clause of the declaration of this
* {@code Class} object.
*
* <p> If this {@code Class} object represents a class or interface whose
* declaration does not explicitly indicate any annotated superinterfaces,
* the return value is an array of length 0.
*
* <p> If this {@code Class} object represents either the {@code Object}
* class, an array type, a primitive type, or void, the return value is an
* array of length 0.
*
* @return an array representing the superinterfaces
* @since 1.8
*/
public AnnotatedType[] getAnnotatedInterfaces() {
return TypeAnnotationParser.buildAnnotatedInterfaces(getRawTypeAnnotations(), getConstantPool(), this);
}
}
Class.java
4.1 获取类名信息
Class类的成员方法 getSimpleName、getName 可以获取到类名相关的信息
技巧01：虽然参数类型是Object类型，但是实际上传递过来的实参是哪个类的对象，c就是哪个类的类类型
例如：传入的 String 的一个实例，那么 c 就是 String 的类类型
public static void printClassInfo(Object object) {
// 01 获取类类型
Class c = object.getClass();
// 02 调用Class实例的相关方法获取类名信息
System.out.println("类的名称为：" + c.getSimpleName());
System.out.println("类的全名为：" + c.getName());
}
4.2 获取方法信息
技巧01：所有的方法都是Method的实例
技巧02：Class类的getMethods获取的是本类以及父类中public修饰的方法;Class类的getDeclaredMethods()获取到的是本类中所有的方法【不包括父类的】
技巧03：Method类的相关成员方法
getReturnType -> 获取方法返回类型 -> 返回值是一个Class实例
getName -> 获取方法名 -> 返回值是一个String实例
getParameterTypes -> 获取方法的参数类型列表 -> 返回值是一个 Class实例 组成的数组
public static void printMethodsInfo(Object object) {
// 01 获取类类型
Class c = object.getClass();
// 技巧01：虽然参数类型是Object类型，但是实际上传递过来的实参是哪个类的对象，c就是哪个类的类类型
// 例如：传入的 String 的一个实例，那么 c 就是 String 的类类型
// 02 获取所有的方法组成的数组
// 技巧02：所有的方法都是Method的实例
// 技巧03：getMethods获取的是本类以及父类中public修饰的方法;getDeclaredMethods()获取到的是本类中所有的方法【不包括父类的】
Method[] methods = c.getMethods();
for (Integer i = 0; i < methods.length; i++) {
// 0201 获取方法返回值类型
Class returnType = methods[i].getReturnType();
System.out.println("第" + i + "个方法的返回值类型为：" + returnType.getName());
// 0202 获取方法名称
String methodName = methods[i].getName();
System.out.println("第" + i + "个方法的方法名为：" + methodName);
// 0203 获取方法参数
Class[] paramTypes = methods[i].getParameterTypes();
for (Integer j = 0; j < paramTypes.length; j++) {
System.out.println("第" + i + "个方法的第" + j + "个参数类型为：" + paramTypes[j].getName());
}
}
}
4.3 获取属性信息
技巧01：所有属性都是Filed的实例
技巧02：Class类的getFields获取public修饰的成员变量，Class类的getDeclaredFields获取本类声明的所有成员
技巧03：Field类的相关方法
getType -> 获取属性类型 -> 返回值是一个Class实例
getName -> 获取属性名称 -> 返回值是一个String实例
public static void printFieldInfo(Object object) {
// 01 获取类类型
Class c = object.getClass();
Field[] fields = c.getFields();
for (Integer i = 0; i < fields.length; i++) {
String fieldName = fields[i].getName();
String fieldType = fields[i].getType().getName();
System.out.println("第" + i + "个成员变量的信息为：字段类型 -> " + fieldType + " 字段名称 -> " + fieldName);
}
}
4.4 获取构造器信息
技巧01：所有的构造器都是Constructor的实例
技巧02：Class类的 getConstructors 获取本类和父类中有pulbic修饰的构造器，Class类的 getDeclaredConstructors 获取本类中声明的构造器
技巧03：Constructor类的相关方法
getName -> 获取构造器名称 -> 返回的是一个String实例
getParameterTypes -> 获取构造器参数类型列表 -> 返回的是一个Class实例组成的数组
public static void printConstructorInfo(Object object) {
// 01 获取类类型
Class c = object.getClass();
Constructor[] constructors = c.getConstructors();
for (Integer i = 0; i < constructors.length; i++) {
String constructorName = constructors[i].getName();
System.out.println("第" + i + "个构造函数逇名称为：" + constructorName);
Class[] paramTypes = constructors[i].getParameterTypes();
for (Integer j = 0; j < paramTypes.length; j++) {
System.out.println("第" + i + "个构造函数的" + "第" + j + "个参数类型为：" + paramTypes[j].getName() );
}
}
}
4.5 代码汇总
package demo_test02; import org.omg.CORBA.OBJECT_NOT_EXIST; import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList; /**
* @author 王杨帅
* @create 2018-08-06 10:34
* @desc
**/
public class Test01 { public static void main(String[] args) {
Integer i = 3;
ClassUtil.printClassInfo(i);
System.out.println("============"); ClassUtil.printMethodsInfo(i);
System.out.println("============"); ClassUtil.printFieldInfo(i);
System.out.println("============"); ClassUtil.printConstructorInfo(i); } } class ClassUtil { public static void printClassInfo(Object object) {
// 01 获取类类型
Class c = object.getClass(); // 02 调用Class实例的相关方法获取类名信息
System.out.println("类的名称为：" + c.getSimpleName());
System.out.println("类的全名为：" + c.getName());
} public static void printMethodsInfo(Object object) {
// 01 获取类类型
Class c = object.getClass();
// 技巧01：虽然参数类型是Object类型，但是实际上传递过来的实参是哪个类的对象，c就是哪个类的类类型
// 例如：传入的 String 的一个实例，那么 c 就是 String 的类类型 // 02 获取所有的方法组成的数组
// 技巧02：所有的方法都是Method的实例
// 技巧03：getMethods获取的是本类以及父类中public修饰的方法;getDeclaredMethods()获取到的是本类中所有的方法【不包括父类的】
Method[] methods = c.getMethods();
for (Integer i = 0; i < methods.length; i++) {
// 0201 获取方法返回值类型
Class returnType = methods[i].getReturnType();
System.out.println("第" + i + "个方法的返回值类型为：" + returnType.getName()); // 0202 获取方法名称
String methodName = methods[i].getName();
System.out.println("第" + i + "个方法的方法名为：" + methodName); // 0203 获取方法参数
Class[] paramTypes = methods[i].getParameterTypes();
for (Integer j = 0; j < paramTypes.length; j++) {
System.out.println("第" + i + "个方法的第" + j + "个参数类型为：" + paramTypes[j].getName());
}
}
} public static void printFieldInfo(Object object) {
// 01 获取类类型
Class c = object.getClass(); Field[] fields = c.getFields(); for (Integer i = 0; i < fields.length; i++) {
String fieldName = fields[i].getName();
String fieldType = fields[i].getType().getName();
System.out.println("第" + i + "个成员变量的信息为：字段类型 -> " + fieldType + " 字段名称 -> " + fieldName);
}
} public static void printConstructorInfo(Object object) { // 01 获取类类型
Class c = object.getClass(); Constructor[] constructors = c.getConstructors();
for (Integer i = 0; i < constructors.length; i++) {
String constructorName = constructors[i].getName();
System.out.println("第" + i + "个构造函数逇名称为：" + constructorName); Class[] paramTypes = constructors[i].getParameterTypes();
for (Integer j = 0; j < paramTypes.length; j++) {
System.out.println("第" + i + "个构造函数的" + "第" + j + "个参数类型为：" + paramTypes[j].getName() );
} } } }
5 方法反射
Method类的invoke方法可以执行一个实例的方法；
一个Class实例可以通过getMethod方法获取到单个的Method实例。
5.1 准备类
class Foo {
public void print() {
System.out.println("渝足");
}
public void print(Integer a, Integer b) {
System.out.println(a + b);
}
public void print(String a, String b) {
System.out.println(a.toUpperCase() + " , " + b.toLowerCase());
}
}
Foo.java
5.2 获取Method实例并用其调用Foo实例的方法
》创建一个Foo实例
》Method实例
// 根据方法名和方法类型列表获取方法对象
Method method0 = c.getMethod("print", new Class[]{String.class, String.class});
》利用Method实例调用Foo实例的方法
// 执行方法对象
method0.invoke(foo, new String[]{"hello", "Fury"});
5.3 代码汇总
package demo06_reflect.case04_method; import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method; /**
* @author 王杨帅
* @create 2018-08-06 9:21
* @desc 方法反射
**/
public class Method_Demo01 { public static void main(String[] args) { Foo foo = new Foo();
// foo.print(1, 2);
// foo.print("hello", "word"); Class c = foo.getClass();
try {
// 根据方法名和方法类型列表获取方法对象
Method method0 = c.getMethod("print", new Class[]{String.class, String.class});
// 执行方法对象
method0.invoke(foo, new String[]{"hello", "Fury"});
// Method method = c.getMethod("print", String.class, String.class);
// method.invoke(foo, "good", "boy");
System.out.println("===================="); Method method1 = c.getMethod("print", Integer.class, Integer.class);
method1.invoke(foo, 3, 4);
Method method2 = c.getMethod("print", new Class[]{Integer.class, Integer.class});
method2.invoke(foo, new Integer[]{4, 4});
System.out.println("===================="); // Method method3 = c.getMethod("print");
// method3.invoke(foo);
Method method4 = c.getMethod("print", new Class[]{});
method4.invoke(foo, new Object[]{});
System.out.println("===================="); } catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} } } class Foo { public void print() {
System.out.println("渝足");
} public void print(Integer a, Integer b) {
System.out.println(a + b);
} public void print(String a, String b) {
System.out.println(a.toUpperCase() + " , " + b.toLowerCase());
}
}
5.4 方法反射的应用
列表的泛型其实是在编译阶段起作用的；所以在运行阶段可以利用方法反射去掉用List的add方法，从而绕过泛型的限制
package demo06_reflect.case04_method; import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List; /**
* @author 王杨帅
* @create 2018-08-06 9:33
* @desc 方法反射的应用
**/
public class Method_Demo02 { public static void main(String[] args) {
List list01 = new ArrayList();
list01.add(333);
list01.add("warrior");
System.out.println(list01); List<String> list02 = new ArrayList<>();
list02.add("warrior");
// list02.add(333);
System.out.println(list02);
System.out.println("==============================="); Class c01 = list01.getClass(); // 运行阶段执行
Class c02 = list02.getClass(); System.out.println(c01 == c02); // 说明列表的泛型只是作用于编译阶段
System.out.println("==============================="); Class c = list02.getClass();
try {
// 获取Method实例
Method method = c.getMethod("add", Object.class);
// 利用Method实例调用List的add方法
method.invoke(list02, 333);
System.out.println(list02);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
}
System.out.println("==============================="); }
}
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