我们在之前的文章简单的介绍了BeanFactory，现在看下源码。
启动
我们看下之前的代码
ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
// 获取xml文件。生成Resource
Resource res = resolver.getResource("classpath:resource/spring-config.xml");
// 创建DefaultListableBeanFactory对象
DefaultListableBeanFactory factory = new DefaultListableBeanFactory();
XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(factory);
// 初始化BeanFactory
reader.loadBeanDefinitions(res);
Resource —— getResource
这里实现的是：PathMatchingResourcePatternResolver类的getResource
/**
* Return the ResourceLoader that this pattern resolver works with.
*/
public ResourceLoader getResourceLoader() {
return this.resourceLoader;
}
@Override
public Resource getResource(String location) {
return getResourceLoader().getResource(location);
}
new DefaultListableBeanFactory();
/**
* Create a new DefaultListableBeanFactory.
*/
public DefaultListableBeanFactory() {
super();
}
/**
* Create a new AbstractAutowireCapableBeanFactory.
*/
public AbstractAutowireCapableBeanFactory() {
super();
ignoreDependencyInterface(BeanNameAware.class);
ignoreDependencyInterface(BeanFactoryAware.class);
ignoreDependencyInterface(BeanClassLoaderAware.class);
}
/**
* Create a new AbstractBeanFactory.
*/
public AbstractBeanFactory() {
}
我们可以看到不仅仅是创建了一个DefaultListableBeanFactory对象，同时还创建了：AbstractAutowireCapableBeanFactory，AbstractBeanFactory两个对象。
new XmlBeanDefinitionReader(factory);
/**
* Create new XmlBeanDefinitionReader for the given bean factory.
* @param registry the BeanFactory to load bean definitions into,
* in the form of a BeanDefinitionRegistry
*/
public XmlBeanDefinitionReader(BeanDefinitionRegistry registry) {
super(registry);
}
// 父类
protected AbstractBeanDefinitionReader(BeanDefinitionRegistry registry) {
Assert.notNull(registry, "BeanDefinitionRegistry must not be null");
this.registry = registry;
// Determine ResourceLoader to use.
if (this.registry instanceof ResourceLoader) {
this.resourceLoader = (ResourceLoader) this.registry;
}
else {
this.resourceLoader = new PathMatchingResourcePatternResolver();
}
// Inherit Environment if possible
if (this.registry instanceof EnvironmentCapable) {
this.environment = ((EnvironmentCapable) this.registry).getEnvironment();
}
else {
this.environment = new StandardEnvironment();
}
}
loadBeanDefinitions
/**
* Load bean definitions from the specified XML file.
* @param resource the resource descriptor for the XML file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
@Override
public int loadBeanDefinitions(Resource resource) throws BeanDefinitionStoreException {
return loadBeanDefinitions(new EncodedResource(resource));
}
下面是重载的方法
/**
* Load bean definitions from the specified XML file.
* @param encodedResource the resource descriptor for the XML file,
* allowing to specify an encoding to use for parsing the file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
*/
public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
Assert.notNull(encodedResource, "EncodedResource must not be null");
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<EncodedResource>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
try {
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close();
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
}
其实可以看成两部分代码
第一部分：
// 如果资源文件不是空的话，
Assert.notNull(encodedResource, "EncodedResource must not be null");
// 判断是否启用了信息日志记录
if (logger.isInfoEnabled()) {
logger.info("Loading XML bean definitions from " + encodedResource.getResource());
}
// 将资源设置为当前Resource
Set<EncodedResource> currentResources = this.resourcesCurrentlyBeingLoaded.get();
if (currentResources == null) {
currentResources = new HashSet<EncodedResource>(4);
this.resourcesCurrentlyBeingLoaded.set(currentResources);
}
if (!currentResources.add(encodedResource)) {
throw new BeanDefinitionStoreException(
"Detected cyclic loading of " + encodedResource + " - check your import definitions!");
}
第二部分：
try {
// 将Resource还原为InputStream流。
InputStream inputStream = encodedResource.getResource().getInputStream();
try {
// 再将InputStream流转换为InputSource — 对XML实体的一个单个输入源
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
// 核心方法：doLoadBeanDefinitions。
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
}
finally {
inputStream.close();
}
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(
"IOException parsing XML document from " + encodedResource.getResource(), ex);
}
finally {
currentResources.remove(encodedResource);
if (currentResources.isEmpty()) {
this.resourcesCurrentlyBeingLoaded.remove();
}
}
doLoadBeanDefinitions
/**
* Actually load bean definitions from the specified XML file.
* 实际上从指定的XML文件加载bean定义。
* @param inputSource the SAX InputSource to read from
* @param resource the resource descriptor for the XML file
* @return the number of bean definitions found
* @throws BeanDefinitionStoreException in case of loading or parsing errors
* @see #doLoadDocument
* @see #registerBeanDefinitions
*/
protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
Document doc = doLoadDocument(inputSource, resource);
return registerBeanDefinitions(doc, resource);
}
catch (BeanDefinitionStoreException ex) {
throw ex;
}
catch (SAXParseException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"Line " + ex.getLineNumber() + " in XML document from " + resource + " is invalid", ex);
}
catch (SAXException ex) {
throw new XmlBeanDefinitionStoreException(resource.getDescription(),
"XML document from " + resource + " is invalid", ex);
}
catch (ParserConfigurationException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Parser configuration exception parsing XML from " + resource, ex);
}
catch (IOException ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"IOException parsing XML document from " + resource, ex);
}
catch (Throwable ex) {
throw new BeanDefinitionStoreException(resource.getDescription(),
"Unexpected exception parsing XML document from " + resource, ex);
}
}
其中核心代码为：
// 将资源文件转成Document对象
Document doc = doLoadDocument(inputSource, resource);
// 将Document对象注册成为Bean。
return registerBeanDefinitions(doc, resource);
看下Document对象：
Document
我们看下Document接口介绍
package org.w3c.dom;
/**
* The <code>Document</code> interface represents the entire HTML or XML
* document. Conceptually, it is the root of the document tree, and provides
* the primary access to the document's data.
*
* 翻译：
* Document接口代表全部的 HTML 或者 XML文件。
* 概念上，他是整个文件树的根，同时给文件的数据提供最主要的入口。
*/
同时要确定一点，Document接口是W3C的，并不是Spring的。
看下registerBeanDefinitions方法：
registerBeanDefinitions
/**
* Register the bean definitions contained in the given DOM document.
* 注册包含在给定DOM文档中的bean定义。
* Called by {@code loadBeanDefinitions}.
* <p>Creates a new instance of the parser class and invokes
* 。。。
* 返回发现bean定义的数目
* @return the number of bean definitions found
* 。。。
*/
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
// 获取BeanDefinitionDocumentReader对象
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
// 返回注册表中定义的bean的数目。
int countBefore = getRegistry().getBeanDefinitionCount();
// 更新BeanDefinitionDocumentReader对象
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}
两个主要的方法：createBeanDefinitionDocumentReader和registerBeanDefinitions
createBeanDefinitionDocumentReader
/**
* Create the {@link BeanDefinitionDocumentReader} to use for actually
* reading bean definitions from an XML document.
* <p>The default implementation instantiates the specified "documentReaderClass".
* @see #setDocumentReaderClass
* 翻译：
* 创建BeanDefinitionDocumentReader，用于实际读取XML文档中的bean定义。
* <P>默认实现实例化指定的“DopeCudieCrar类”。
*/
protected BeanDefinitionDocumentReader createBeanDefinitionDocumentReader() {
return BeanDefinitionDocumentReader.class.cast(BeanUtils.instantiateClass(this.documentReaderClass));
}
registerBeanDefinitions
/**
* This implementation parses bean definitions according to the "spring-beans" XSD
* (or DTD, historically).
* <p>Opens a DOM Document; then initializes the default settings
* specified at the {@code <beans/>} level; then parses the contained bean definitions.
* 翻译：
* 此实现根据“Spring Bean”XSD（或DTD，历史上）解析bean定义。
* <p>打开DOM文档；然后初始化在该级别指定的默认设置；然后解析包含的bean定义。
*/
@Override
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}
