lombok使用及常用注解
简介
大部分项目中都必不可少的包含数据库实体(Entity)、数据载体(dto,dataObject),而这两部分都包含着大量的没有业务逻辑的setter、getter、空参构造，同时我们一般要复写类的toString(),equals(),hashCode()方法(贫血模型)。这些工作都是重复性的工作，作为程序员，懒是必备素质之一，这些工作肯定已经有大牛封装好了处理方法,这就是lombok。
idea 安装插件，支持lombok
lombok是在编译阶段才生成相应的代码体，所以在项目中直接调用setter，getter,constructor会报错，这时候可以在IDE安装相应的插件支持lombok。这里介绍idea插件安装，eclipse请自行百度。
安装方法
- 进入设置页面(windows:setting,Mac:Preferences)
- 点击Plugin
- Browse repositories
- 搜索lombok
- 点击Install
- 安装完毕后开启注解权限才能正常使用:
- –>setting
- –>Build,Execution,Deployment
- –>Compiler
- –>Annontation Processors
- –>勾选
Enable annotation processing - –> Apply
- 重启Idea
引入方法
gradle
// https://mvnrepository.com/artifact/org.projectlombok/lombok
compile group: 'org.projectlombok', name: 'lombok', version: '1.16.16'
maven
<!-- https://mvnrepository.com/artifact/org.projectlombok/lombok -->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.16.16</version>
</dependency>常用方法
@Setter
生成setter方法,final变量不包含
//原始类
@Setter
public class TestEntity { private String name; private Integer age; private final String type = "type";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public void setName(String name) {
this.name = name;
} public void setAge(Integer age) {
this.age = age;
}
}@Getter
生成getter方法,final变量不包含
//原始类
@Getter
public class TestEntity { private String name; private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public String getName() {
return this.name;
} public Integer getAge() {
return this.age;
} public String getType() {
this.getClass();
return "person";
}
}@NoArgsConstructor
生成空参构造
//原始类
@NoArgsConstructor
public class TestEntity { private String name; private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
}
}@AllArgsConstructor
生成全部参数构造
//原始类
@AllArgsConstructor
public class TestEntity { private String name; private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; @ConstructorProperties({"name", "age"})
public TestEntity(String name, Integer age) {
this.name = name;
this.age = age;
}
}@RequiredArgsConstructor
将标记为@NoNull的属性生成一个构造器
如果运行中标记为@NoNull的属性为null,会抛出空指针异常。
//原始类
@RequiredArgsConstructor
public class TestEntity { private String name;
@NonNull
private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
@NonNull
private Integer age;
private final String type = "person"; @ConstructorProperties({"age"})
public TestEntity(@NonNull Integer age) {
if(age == null) {
throw new NullPointerException("age");
} else {
this.age = age;
}
}
}@ToString
生成所有属性的toString()方法
//原始类
@ToString
public class TestEntity { private String name; private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public String toString() {
StringBuilder var10000 = (new StringBuilder()).append("TestEntity(name=").append(this.name).append(", age=").append(this.age).append(", type=");
this.getClass();
return var10000.append("person").append(")").toString();
}
}@EqualsAndHashCode
生成equals()方法和hashCode方法
//原始类
@EqualsAndHashCode
public class TestEntity { private String name; private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public boolean equals(Object o) {
if(o == this) {
return true;
} else if(!(o instanceof TestEntity)) {
return false;
} else {
TestEntity other = (TestEntity)o;
if(!other.canEqual(this)) {
return false;
} else {
label47: {
String this$name = this.name;
String other$name = other.name;
if(this$name == null) {
if(other$name == null) {
break label47;
}
} else if(this$name.equals(other$name)) {
break label47;
} return false;
} Integer this$age = this.age;
Integer other$age = other.age;
if(this$age == null) {
if(other$age != null) {
return false;
}
} else if(!this$age.equals(other$age)) {
return false;
} this.getClass();
String this$type = "person";
other.getClass();
String other$type = "person";
if(this$type == null) {
if(other$type != null) {
return false;
}
} else if(!this$type.equals(other$type)) {
return false;
} return true;
}
}
} protected boolean canEqual(Object other) {
return other instanceof TestEntity;
} public int hashCode() {
boolean PRIME = true;
byte result = 1;
String $name = this.name;
int result1 = result * 59 + ($name == null?43:$name.hashCode());
Integer $age = this.age;
result1 = result1 * 59 + ($age == null?43:$age.hashCode());
this.getClass();
String $type = "person";
result1 = result1 * 59 + ($type == null?43:$type.hashCode());
return result1;
}
}@Data(常用)
@Data直接修饰POJO or beans， getter所有的变量，setter所有不为final的变量。如果你不需要默认的生成方式，直接填写你需要的annotation的就可以了。默认生成的所有的annotation都是public的，如果需要不同权限修饰符可以使用AccessLevel.NONE选项。当然@Data 也可以使用staticConstructor选项生成一个静态方法。
=@Setter+@Getter+@EqualsAndHashCode+@NoArgsConstructor
//原始类
@Data
public class TestEntity {
@Setter(AccessLevel.PRIVATE)
private String name; private Integer age; private final String type = "person";
}
//反编译的类 public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public String getName() {
return this.name;
} public Integer getAge() {
return this.age;
} public String getType() {
this.getClass();
return "person";
} public void setAge(Integer age) {
this.age = age;
} public boolean equals(Object o) {
if(o == this) {
return true;
} else if(!(o instanceof TestEntity)) {
return false;
} else {
TestEntity other = (TestEntity)o;
if(!other.canEqual(this)) {
return false;
} else {
label47: {
String this$name = this.getName();
String other$name = other.getName();
if(this$name == null) {
if(other$name == null) {
break label47;
}
} else if(this$name.equals(other$name)) {
break label47;
} return false;
} Integer this$age = this.getAge();
Integer other$age = other.getAge();
if(this$age == null) {
if(other$age != null) {
return false;
}
} else if(!this$age.equals(other$age)) {
return false;
} String this$type = this.getType();
String other$type = other.getType();
if(this$type == null) {
if(other$type != null) {
return false;
}
} else if(!this$type.equals(other$type)) {
return false;
} return true;
}
}
} protected boolean canEqual(Object other) {
return other instanceof TestEntity;
} public int hashCode() {
boolean PRIME = true;
byte result = 1;
String $name = this.getName();
int result1 = result * 59 + ($name == null?43:$name.hashCode());
Integer $age = this.getAge();
result1 = result1 * 59 + ($age == null?43:$age.hashCode());
String $type = this.getType();
result1 = result1 * 59 + ($type == null?43:$type.hashCode());
return result1;
} public String toString() {
return "TestEntity(name=" + this.getName() + ", age=" + this.getAge() + ", type=" + this.getType() + ")";
} private void setName(String name) {
this.name = name;
}
}@Builder
构造Builder模式的结构。通过内部类Builder()进行构建对象。
//原始类
@Builder
public class TestEntity { private String name; private Integer age; private final String type = "person";
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; @ConstructorProperties({"name", "age"})
TestEntity(String name, Integer age) {
this.name = name;
this.age = age;
} public static TestEntity.TestEntityBuilder builder() {
return new TestEntity.TestEntityBuilder();
} public static class TestEntityBuilder {
private String name;
private Integer age; TestEntityBuilder() {
} public TestEntity.TestEntityBuilder name(String name) {
this.name = name;
return this;
} public TestEntity.TestEntityBuilder age(Integer age) {
this.age = age;
return this;
} public TestEntity build() {
return new TestEntity(this.name, this.age);
} public String toString() {
return "TestEntity.TestEntityBuilder(name=" + this.name + ", age=" + this.age + ")";
}
}
} //Builder模式使用方法
@Test
public void test(){
TestEntity testEntity = TestEntity.builder()
.name("java")
.age(18)
.build();
}@Value
与@Data相对应的@Value， 两个annotation的主要区别就是如果变量不加@NonFinal ，@Value会给所有的弄成final的。当然如果是final的话，就没有set方法了。
//原始类
@Value
public class TestEntity {
@Setter(AccessLevel.PRIVATE)
private String name; private Integer age; private final String type = "person";
}
//反编译的类
public final class TestEntity {
private final String name;
private final Integer age;
private final String type = "person"; @ConstructorProperties({"name", "age"})
public TestEntity(String name, Integer age) {
this.name = name;
this.age = age;
} public String getName() {
return this.name;
} public Integer getAge() {
return this.age;
} public String getType() {
this.getClass();
return "person";
} public boolean equals(Object o) {
if(o == this) {
return true;
} else if(!(o instanceof TestEntity)) {
return false;
} else {
TestEntity other;
label44: {
other = (TestEntity)o;
String this$name = this.getName();
String other$name = other.getName();
if(this$name == null) {
if(other$name == null) {
break label44;
}
} else if(this$name.equals(other$name)) {
break label44;
} return false;
} Integer this$age = this.getAge();
Integer other$age = other.getAge();
if(this$age == null) {
if(other$age != null) {
return false;
}
} else if(!this$age.equals(other$age)) {
return false;
} String this$type = this.getType();
String other$type = other.getType();
if(this$type == null) {
if(other$type != null) {
return false;
}
} else if(!this$type.equals(other$type)) {
return false;
} return true;
}
} public int hashCode() {
boolean PRIME = true;
byte result = 1;
String $name = this.getName();
int result1 = result * 59 + ($name == null?43:$name.hashCode());
Integer $age = this.getAge();
result1 = result1 * 59 + ($age == null?43:$age.hashCode());
String $type = this.getType();
result1 = result1 * 59 + ($type == null?43:$type.hashCode());
return result1;
} public String toString() {
return "TestEntity(name=" + this.getName() + ", age=" + this.getAge() + ", type=" + this.getType() + ")";
}
}@Synchronized
同步方法
//原始类
public class TestEntity {
private String name; private Integer age; private final String type = "person";
@Synchronized
public void write(){
//do something
}
}
//反编译的类
public class TestEntity {
private final Object $lock = new Object[0];
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public void write() {
Object var1 = this.$lock;
synchronized(this.$lock) {
;
}
}
}@Cleanup @@SneakyThrows
自动调用close方法关闭资源。
//原始类
public class TestEntity {
private String name; private Integer age; private final String type = "person"; @SneakyThrows
public void outputStream(){
@Cleanup OutputStream outputStream = new FileOutputStream(new File("/Users/hello"));
}
}
//反编译的类
public class TestEntity {
private String name;
private Integer age;
private final String type = "person"; public TestEntity() {
} public void outputStream() {
try {
FileOutputStream $ex = new FileOutputStream(new File("/Users/hello"));
if(Collections.singletonList($ex).get(0) != null) {
$ex.close();
} } catch (Throwable var2) {
throw var2;
}
}
}原文链接：https://blog.csdn.net/u013225178/article/details/80721799
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