Spring源码之DefaultListableBeanFactory及资源载入
1、XmlBeanFactory 的使用,参考MyEclipse Spring 学习总结一 Spring IOC容器
public static void main(String[] args) {
XmlBeanFactory factory = new XmlBeanFactory(new ClassPathResource("applicationContext.xml"));
HelloWorld obj = (HelloWorld)factory.getBean("helloWorld");
obj.getMessage(); }
2、使用DefaultListableBeanFactory和XmlBeanDefinitionReader
ClassPathResource resource = new ClassPathSource("beans.xml");
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
reader.loadBeanDefinitions(resource);
Spring加载资源并装配对象的过程
1、定义好Spring的配置文件
2、通过Resource将Spring配置文件进行抽象,抽象成一个Resource对象
3、定义好Bean工厂(各种BeanFactory)
4、定义好XmlBeanDefinitionReader对象,并将工厂对象作为参数传递进去供后续回调使用。
5、通过XmlBeanDefinitionReader对象读取之前抽象出的Resource对象(包含了XML文件的解析过程)
6、本质上,XML文件的解析是有XmlBeanDefinitionReader对象交由BeanDefinitionParserDelegate委托来完成的。实质上这里使用到类委托模式。
7、Ioc容器创建完毕,用户可以通过容器获取所需的对象信息。
3、查看ClassPathResource
首先查看InputStreamSource接口,里面定义了一个getInputStream方法
public interface InputStreamSource { /**
* Return an {@link InputStream}.
* <p>It is expected that each call creates a <i>fresh</i> stream.
* <p>This requirement is particularly important when you consider an API such
* as JavaMail, which needs to be able to read the stream multiple times when
* creating mail attachments. For such a use case, it is <i>required</i>
* that each <code>getInputStream()</code> call returns a fresh stream.
* @throws IOException if the stream could not be opened
* @see org.springframework.mail.javamail.MimeMessageHelper#addAttachment(String, InputStreamSource)
*/
InputStream getInputStream() throws IOException; }
然后查看Resource接口
public interface Resource extends InputStreamSource { /**
* Return whether this resource actually exists in physical form.
* <p>This method performs a definitive existence check, whereas the
* existence of a <code>Resource</code> handle only guarantees a
* valid descriptor handle.
*/
boolean exists(); /**
* Return whether the contents of this resource can be read,
* e.g. via {@link #getInputStream()} or {@link #getFile()}.
* <p>Will be <code>true</code> for typical resource descriptors;
* note that actual content reading may still fail when attempted.
* However, a value of <code>false</code> is a definitive indication
* that the resource content cannot be read.
* @see #getInputStream()
*/
boolean isReadable(); /**
* Return whether this resource represents a handle with an open
* stream. If true, the InputStream cannot be read multiple times,
* and must be read and closed to avoid resource leaks.
* <p>Will be <code>false</code> for typical resource descriptors.
*/
boolean isOpen(); /**
* Return a URL handle for this resource.
* @throws IOException if the resource cannot be resolved as URL,
* i.e. if the resource is not available as descriptor
*/
URL getURL() throws IOException; /**
* Return a URI handle for this resource.
* @throws IOException if the resource cannot be resolved as URI,
* i.e. if the resource is not available as descriptor
*/
URI getURI() throws IOException; /**
* Return a File handle for this resource.
* @throws IOException if the resource cannot be resolved as absolute
* file path, i.e. if the resource is not available in a file system
*/
File getFile() throws IOException; /**
* Determine the content length for this resource.
* @throws IOException if the resource cannot be resolved
* (in the file system or as some other known physical resource type)
*/
long contentLength() throws IOException; /**
* Determine the last-modified timestamp for this resource.
* @throws IOException if the resource cannot be resolved
* (in the file system or as some other known physical resource type)
*/
long lastModified() throws IOException; /**
* Create a resource relative to this resource.
* @param relativePath the relative path (relative to this resource)
* @return the resource handle for the relative resource
* @throws IOException if the relative resource cannot be determined
*/
Resource createRelative(String relativePath) throws IOException; /**
* Determine a filename for this resource, i.e. typically the last
* part of the path: for example, "myfile.txt".
* <p>Returns <code>null</code> if this type of resource does not
* have a filename.
*/
String getFilename(); /**
* Return a description for this resource,
* to be used for error output when working with the resource.
* <p>Implementations are also encouraged to return this value
* from their <code>toString</code> method.
* @see java.lang.Object#toString()
*/
String getDescription(); /**
* {@inheritDoc}
* @return the input stream for the underlying resource (must not be {@code null}).
*/
public InputStream getInputStream() throws IOException;
}
4、ClassPathResource 源码
public class ClassPathResource extends AbstractFileResolvingResource { private final String path; private ClassLoader classLoader; private Class<?> clazz; /**
* Create a new ClassPathResource for ClassLoader usage.
* A leading slash will be removed, as the ClassLoader
* resource access methods will not accept it.
* <p>The thread context class loader will be used for
* loading the resource.
* @param path the absolute path within the class path
* @see java.lang.ClassLoader#getResourceAsStream(String)
* @see org.springframework.util.ClassUtils#getDefaultClassLoader()
*/
public ClassPathResource(String path) {
this(path, (ClassLoader) null);
} /**
* Create a new ClassPathResource for ClassLoader usage.
* A leading slash will be removed, as the ClassLoader
* resource access methods will not accept it.
* @param path the absolute path within the classpath
* @param classLoader the class loader to load the resource with,
* or <code>null</code> for the thread context class loader
* @see java.lang.ClassLoader#getResourceAsStream(String)
*/
public ClassPathResource(String path, ClassLoader classLoader) {
Assert.notNull(path, "Path must not be null");
String pathToUse = StringUtils.cleanPath(path);
if (pathToUse.startsWith("/")) {
pathToUse = pathToUse.substring(1);
}
this.path = pathToUse;
this.classLoader = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
} /**
* Create a new ClassPathResource for Class usage.
* The path can be relative to the given class,
* or absolute within the classpath via a leading slash.
* @param path relative or absolute path within the class path
* @param clazz the class to load resources with
* @see java.lang.Class#getResourceAsStream
*/
public ClassPathResource(String path, Class<?> clazz) {
Assert.notNull(path, "Path must not be null");
this.path = StringUtils.cleanPath(path);
this.clazz = clazz;
} /**
* Create a new ClassPathResource with optional ClassLoader and Class.
* Only for internal usage.
* @param path relative or absolute path within the classpath
* @param classLoader the class loader to load the resource with, if any
* @param clazz the class to load resources with, if any
*/
protected ClassPathResource(String path, ClassLoader classLoader, Class<?> clazz) {
this.path = StringUtils.cleanPath(path);
this.classLoader = classLoader;
this.clazz = clazz;
} /**
* Return the path for this resource (as resource path within the class path).
*/
public final String getPath() {
return this.path;
} /**
* Return the ClassLoader that this resource will be obtained from.
*/
public final ClassLoader getClassLoader() {
return (this.classLoader != null ? this.classLoader : this.clazz.getClassLoader());
} /**
* This implementation checks for the resolution of a resource URL.
* @see java.lang.ClassLoader#getResource(String)
* @see java.lang.Class#getResource(String)
*/
@Override
public boolean exists() {
URL url;
if (this.clazz != null) {
url = this.clazz.getResource(this.path);
}
else {
url = this.classLoader.getResource(this.path);
}
return (url != null);
} /**
* This implementation opens an InputStream for the given class path resource.
* @see java.lang.ClassLoader#getResourceAsStream(String)
* @see java.lang.Class#getResourceAsStream(String)
*/
public InputStream getInputStream() throws IOException {
InputStream is;
if (this.clazz != null) {
is = this.clazz.getResourceAsStream(this.path);
}
else {
is = this.classLoader.getResourceAsStream(this.path);
}
if (is == null) {
throw new FileNotFoundException(getDescription() + " cannot be opened because it does not exist");
}
return is;
} /**
* This implementation returns a URL for the underlying class path resource.
* @see java.lang.ClassLoader#getResource(String)
* @see java.lang.Class#getResource(String)
*/
@Override
public URL getURL() throws IOException {
URL url;
if (this.clazz != null) {
url = this.clazz.getResource(this.path);
}
else {
url = this.classLoader.getResource(this.path);
}
if (url == null) {
throw new FileNotFoundException(getDescription() + " cannot be resolved to URL because it does not exist");
}
return url;
} /**
* This implementation creates a ClassPathResource, applying the given path
* relative to the path of the underlying resource of this descriptor.
* @see org.springframework.util.StringUtils#applyRelativePath(String, String)
*/
@Override
public Resource createRelative(String relativePath) {
String pathToUse = StringUtils.applyRelativePath(this.path, relativePath);
return new ClassPathResource(pathToUse, this.classLoader, this.clazz);
} /**
* This implementation returns the name of the file that this class path
* resource refers to.
* @see org.springframework.util.StringUtils#getFilename(String)
*/
@Override
public String getFilename() {
return StringUtils.getFilename(this.path);
} /**
* This implementation returns a description that includes the class path location.
*/
public String getDescription() {
StringBuilder builder = new StringBuilder("class path resource ["); String pathToUse = path; if (this.clazz != null && !pathToUse.startsWith("/")) {
builder.append(ClassUtils.classPackageAsResourcePath(this.clazz));
builder.append('/');
} if (pathToUse.startsWith("/")) {
pathToUse = pathToUse.substring(1);
} builder.append(pathToUse);
builder.append(']');
return builder.toString();
} /**
* This implementation compares the underlying class path locations.
*/
@Override
public boolean equals(Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof ClassPathResource) {
ClassPathResource otherRes = (ClassPathResource) obj;
return (this.path.equals(otherRes.path)
&& ObjectUtils.nullSafeEquals(this.classLoader, otherRes.classLoader) && ObjectUtils.nullSafeEquals(
this.clazz, otherRes.clazz));
}
return false;
} /**
* This implementation returns the hash code of the underlying
* class path location.
*/
@Override
public int hashCode() {
return this.path.hashCode();
} }
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