public static void main(String[] args){
BeanFactory factory=new XmlBeanFactory(new ClassPathResource("applicationContext2.xml"));
}我们从这一行代码开始。public class XmlBeanFactory extends DefaultListableBeanFactory {
private final XmlBeanDefinitionReader reader = new XmlBeanDefinitionReader(this);
public XmlBeanFactory(Resource resource) throws BeansException {
this(resource, null);
}
public XmlBeanFactory(Resource resource, BeanFactory parentBeanFactory) throws BeansException {
super(parentBeanFactory);
this.reader.loadBeanDefinitions(resource);
}
}OK,我们之间开始看XmlBeanDefinitionReader的loadBeanDefinitions。(图中的第二步)public int loadBeanDefinitions(EncodedResource encodedResource) throws BeanDefinitionStoreException {
....
InputStream inputStream = encodedResource.getResource().getInputStream();
InputSource inputSource = new InputSource(inputStream);
if (encodedResource.getEncoding() != null) {
inputSource.setEncoding(encodedResource.getEncoding());
}
return doLoadBeanDefinitions(inputSource, encodedResource.getResource());
....
}上面的EncodedResource是对Resource的再包装,不是重点。重点在doLoadBeanDefinitions protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
Document doc = this.documentLoader.loadDocument(
inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware());
return registerBeanDefinitions(doc, resource);
...
//省略try catch
}上面的documentLoader是DefaultDocumentLoader的实例,Document是org.w3c.dom.Document的实例。 //XmlBeanDefinitionReader.java
public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
documentReader.setEnvironment(this.getEnvironment());
int countBefore = getRegistry().getBeanDefinitionCount();
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}countBefore,就是之前已经注册了多少bean。//DefaultBeanDefinitionDocumentReader.java
public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;
logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();
doRegisterBeanDefinitions(root);
}
protected void doRegisterBeanDefinitions(Element root) {
this.delegate = createHelper(readerContext, root, parent);
//preProcessXml与postProcessXml都是空方法
preProcessXml(root);
parseBeanDefinitions(root, this.delegate);
postProcessXml(root);
this.delegate = parent;
}
protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
//<beans xmlns="http://www.springframework.org/schema/beans" />
//查看是否是默认的命名空间
if (delegate.isDefaultNamespace(root)) {
NodeList nl = root.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element) {
Element ele = (Element) node;
if (delegate.isDefaultNamespace(ele)) {
//这一行用来出来bean标签
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}我们看看我调试时的一张图
public static final String NAME_ATTRIBUTE = "name"; public static final String BEAN_ELEMENT = "bean"; public static final String META_ELEMENT = "meta"; public static final String ID_ATTRIBUTE = "id"; public static final String PARENT_ATTRIBUTE = "parent"; public static final String CLASS_ATTRIBUTE = "class"; public static final String ABSTRACT_ATTRIBUTE = "abstract"; .....
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//是否是import节点
if (delegate.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
else if (delegate.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
//是否是bean节点
else if (delegate.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
else if (delegate.nodeNameEquals(ele, NESTED_BEANS_ELEMENT)) {
// recurse
doRegisterBeanDefinitions(ele);
}
}我们抓主要矛盾,看processBeanDefinition,这已经是图中的第十步了。 protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
// Register the final decorated instance.
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}在这里我简单介绍一下BeanDefinitionHolderpublic BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);
String beanName = id;
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);
if (beanDefinition != null) {
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}
return null;
}上面的代码,我已经删去了一部分。//BeanDefinitionParserDelegate.java
public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {
String className = null;
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}
AbstractBeanDefinition bd = createBeanDefinition(className, parent);
parseBeanDefinitionAttributes(ele, beanName, containingBean, bd);
bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));
parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
parseConstructorArgElements(ele, bd);
parsePropertyElements(ele, bd);
parseQualifierElements(ele, bd);
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));
return bd;
}parseLookupOverrideSubElements,parseConstructorArgElements,parsePropertyElements大家能猜出来里面是干什么的吗?//DefaultBeanDefinitionDocumentReader.java
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
//十一步
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
// Register the final decorated instance.
//十二步
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
//BeanDefinitionReaderUtils.java
public static void registerBeanDefinition(
BeanDefinitionHolder definitionHolder, BeanDefinitionRegistry registry)
throws BeanDefinitionStoreException {
// Register bean definition under primary name.
String beanName = definitionHolder.getBeanName();
registry.registerBeanDefinition(beanName, definitionHolder.getBeanDefinition());
}大家得记得,我们的容器,XmlBeanFactory本身也实现了BeanDefinitionRegistry。 //DefaultListableBeanFactory.java
public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {
this.beanDefinitionNames.add(beanName);
this.beanDefinitionMap.put(beanName, beanDefinition);
resetBeanDefinition(beanName);
}beanDefinitionMap里面维护着整个容器里面的bean。版权声明：本文为博主原创文章，未经博主允许不得转载。
Spring揭秘 读书笔记 七 BeanFactory的启动分析
原文：http://blog.csdn.net/dlf123321/article/details/47984515