Spring源码学习-3.IoC.资源的加载与注册

ApplicationContext中资源加载是IOC容器初始化的第二步,

第一步定位资源已经在上一篇中完成了,这一篇我们就来分析一下,IoC资源是怎么加载到BeanDefinition中的.

refresh()方法出现在FileSystemXmlApplicationContext的构造函数中

public FileSystemXmlApplicationContext(String[] configLocations, boolean refresh, ApplicationContext parent)
throws BeansException {

super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
}
}

refresh()是BeanDefinition加载的入口,下面我们来看refresh方法源码

//这个方法描述了整个ApplicationContext的初始化方法
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
//准备刷新的方法，获取时间，设置同步标志
prepareRefresh();

// Tell the subclass to refresh the internal bean factory.
//调用子类的resfreshFactory()。获得工厂实例
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

// Prepare the bean factory for use in this context.
//初始化：配置容器属性，如ClassLoader,事件处理器
prepareBeanFactory(beanFactory);

try {
// Allows post-processing of the bean factory in context subclasses.
//设置后置处理
postProcessBeanFactory(beanFactory);

// Invoke factory processors registered as beans in the context.
//加载所有参与的Bean
invokeBeanFactoryPostProcessors(beanFactory);

// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);

// Initialize message source for this context.
//初始化信息源，与国际化有关
initMessageSource();

// Initialize event multicaster for this context.
//初始化容器事件传播器
initApplicationEventMulticaster();

// Initialize other special beans in specific context subclasses.
//子类某些特殊Bean初始化方法
//子类重写onRefresh后，到底会调用哪个OnRefresh()?
onRefresh();

// Check for listener beans and register them.
//为传播器注册监听器
registerListeners();

// Instantiate all remaining (non-lazy-init) singletons.
finishBeanFactoryInitialization(beanFactory);

// Last step: publish corresponding event.容器生命周期事件
finishRefresh();
}

catch (BeansException ex) {
// Destroy already created singletons to avoid dangling resources.
beanFactory.destroySingletons();

// Reset 'active' flag.重置同步标识
cancelRefresh(ex);

// Propagate exception to caller.
throw ex;
}
}
}

获取工程实例的代码

protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {
//父类定义了抽象的refreshBeanFactory()方法，具/体实现调用子类容器的refreshBeanFactory()方法
refreshBeanFactory();
ConfigurableListableBeanFactory beanFactory = getBeanFactory();
if (logger.isDebugEnabled()) {
logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);
}
return beanFactory;
}

AbstractApplicationContext的子类 AbstractRefreshableApplicationContext实现了refreshBeanFactory这个抽象方法
关于BeanDefinition的加载全都在子类对于这个方法的实现中

protected final void refreshBeanFactory() throws BeansException {
if (hasBeanFactory()) {
destroyBeans();
closeBeanFactory();
}
try {
DefaultListableBeanFactory beanFactory = createBeanFactory();
customizeBeanFactory(beanFactory);
loadBeanDefinitions(beanFactory);                            //抽象方法 AbstractXmlApplicationContext实现，
//委派模式										// 然后调用AbstractXmlApplicationContext
//的loadBeanDefinitions(XmlBeanDefinitionReader)
synchronized (this.beanFactoryMonitor) {                     //beanFactoryMonitor 监视器
this.beanFactory = beanFactory;
}
}
catch (IOException ex) {
throw new ApplicationContextException(
"I/O error parsing XML document for application context [" + getDisplayName() + "]", ex);
}
}

AbstractXmlApplicationContext中实现了 上面代码中的loadBeanDefinitions(beanFactory)抽象方法

<pre name="code" class="java">

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws IOException {
// Create a new XmlBeanDefinitionReader for the given BeanFactory.
XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);

// Configure the bean definition reader with this context's
// resource loading environment.
beanDefinitionReader.setResourceLoader(this);
beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));

// Allow a subclass to provide custom initialization of the reader,
// then proceed with actually loading the bean definitions.
initBeanDefinitionReader(beanDefinitionReader);
//  BeanDefinition加载开始
loadBeanDefinitions(beanDefinitionReader);
}

//也是这个AbstractXmlApplicationContext类中的方法
//	通过BeanFactory生成了 XmlBeanDefinitionReader
通过Resource和String两种方式加载BeanDefinitions

protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws BeansException, IOException {
Resource[] configResources = getConfigResources();
if (configResources != null) {
reader.loadBeanDefinitions(configResources);
}
String[] configLocations = getConfigLocations();
if (configLocations != null) {
reader.loadBeanDefinitions(configLocations);
}
}

</pre><p>后面的代码中调用了若干个参数不同的loadBeanDefinition方法</p><p></p><p>loadBeanDefinitions的参数变化<span style="white-space: pre;">	</span></p>loadBeanDefinitions(DefaultListableBeanFactory beanFactory) loadBeanDefinitions(String[] locations)loadBeanDefinitions(String location)loadBeanDefinitions(String location, Set actualResources)loadBeanDefinitions(Resource[] resources)loadBeanDefinitions(Resource resource) loadBeanDefinitions(EncodedResource encodedResource)<p>最后调用了 int doLoadBeanDefinitions(InputSource inputSource, Resource resource)这里实现了加载loadBeanDefinitions的代码</p><p><pre name="code" class="java">protected int doLoadBeanDefinitions(InputSource inputSource, Resource resource)
throws BeanDefinitionStoreException {
try {
int validationMode = getValidationModeForResource(resource);
Document doc = this.documentLoader.loadDocument(//解析XML文件,获取Document对象
inputSource, getEntityResolver(), this.errorHandler, validationMode, isNamespaceAware());
// 容器按照Bean语义进行解析，并转化为内部数据结构
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);
}
}

解析XML,获取Document对象的代码:

//	加载Domcument的地方
public Document loadDocument(InputSource inputSource, EntityResolver entityResolver,
ErrorHandler errorHandler, int validationMode, boolean namespaceAware) throws Exception {

DocumentBuilderFactory factory = createDocumentBuilderFactory(validationMode, namespaceAware);
if (logger.isDebugEnabled()) {
logger.debug("Using JAXP provider [" + factory.getClass().getName() + "]");
}
DocumentBuilder builder = createDocumentBuilder(factory, entityResolver, errorHandler);
return builder.parse(inputSource);
}

详细探究XML解析过程:

//	DocumentBuilderImpl 中的parse方法
public Document parse(InputSource is) throws SAXException, IOException {
if (is == null) {
throw new IllegalArgumentException(
DOMMessageFormatter.formatMessage(DOMMessageFormatter.DOM_DOMAIN,
"jaxp-null-input-source", null));
}
if (fSchemaValidator != null) {
if (fSchemaValidationManager != null) {
fSchemaValidationManager.reset();
}
resetSchemaValidator();
}
domParser.parse(is);//开始解析
return domParser.getDocument();//得到Document对象
}

parse和getDocument都是DOMParser下面的两个函数:
具体解析过程没怎么看明白~~

调用了com.sun.org.apache.xerces.internal.parsers.XML11Configuration里面的方法和

XMLVersionDetector里面的startDocumentParsing方法

得到Document以后就是将BeanDefinition信息载入到Map中

//XmlBeanDefinitionReader 中的 注册方法

public int registerBeanDefinitions(Document doc, Resource resource) throws BeanDefinitionStoreException {
// Support old XmlBeanDefinitionParser SPI for backwards-compatibility.
// 不使用这个
if (this.parserClass != null) {
XmlBeanDefinitionParser parser =
(XmlBeanDefinitionParser) BeanUtils.instantiateClass(this.parserClass);
return parser.registerBeanDefinitions(this, doc, resource);
}
// Read document based on new BeanDefinitionDocumentReader SPI.
//
BeanDefinitionDocumentReader documentReader = createBeanDefinitionDocumentReader();
int countBefore = getRegistry().getBeanDefinitionCount();
//            具体解析过程在这里实现
documentReader.registerBeanDefinitions(doc, createReaderContext(resource));
return getRegistry().getBeanDefinitionCount() - countBefore;
}

接下来调用DefaultBeanDefinitionDocumentReader 类封装BeanDefinition

//                 DefaultBeanDefinitionDocumentReader 类

public void registerBeanDefinitions(Document doc, XmlReaderContext readerContext) {
this.readerContext = readerContext;

logger.debug("Loading bean definitions");
Element root = doc.getDocumentElement();

BeanDefinitionParserDelegate delegate = createHelper(readerContext, root);
//	 //在解析Bean定义之前，进行自定义的解析，增强解析过程的可扩展性
preProcessXml(root);
//     这一步为解析过程
parseBeanDefinitions(root, delegate);
//	 //在解析Bean定义之后，进行自定义的解析，增强解析过程的可扩展性
postProcessXml(root);
}

//   		也在DefaultBeanDefinitionDocumentReader这个类中parseBeanDefinitions方法

protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {
//Bean定义的Document对象使用了Spring默认的XML命名空间
if (delegate.isDefaultNamespace(root.getNamespaceURI())) {
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;
String namespaceUri = ele.getNamespaceURI();
if (delegate.isDefaultNamespace(namespaceUri)) {
//	如果使用了默认的，就在此解析
parseDefaultElement(ele, delegate);
}
else {
delegate.parseCustomElement(ele);
}
}
}
}
else {
delegate.parseCustomElement(root);
}
}

接下来就是开始分析XML文件中标签属性了

//默认解析过程
private void parseDefaultElement(Element ele, BeanDefinitionParserDelegate delegate) {
//如果元素节点是<Import>导入元素，进行导入解析
if (DomUtils.nodeNameEquals(ele, IMPORT_ELEMENT)) {
importBeanDefinitionResource(ele);
}
//如果元素节点是<Alias>别名元素，进行别名解析
else if (DomUtils.nodeNameEquals(ele, ALIAS_ELEMENT)) {
processAliasRegistration(ele);
}
// 普通Bean 。进行解析
else if (DomUtils.nodeNameEquals(ele, BEAN_ELEMENT)) {
processBeanDefinition(ele, delegate);
}
}

三种不同情况,分别解析,(产生一个疑问,那Spring配置文件中其他的标签如何加载???)

//       import

protected void importBeanDefinitionResource(Element ele) {
//获取给定的导入元素的location属性
String location = ele.getAttribute(RESOURCE_ATTRIBUTE);
//如果导入元素的location属性值为空，则没有导入任何资源，直接返回
if (!StringUtils.hasText(location)) {
getReaderContext().error("Resource location must not be empty", ele);
return;
}

//使用系统变量值解析location属性值
location = SystemPropertyUtils.resolvePlaceholders(location);
Set<Resource> actualResources = new LinkedHashSet<Resource>(4);
//标识给定的导入元素的location是否是绝对路径
boolean absoluteLocation = false;
try {
absoluteLocation = ResourcePatternUtils.isUrl(location) || ResourceUtils.toURI(location).isAbsolute();
}
catch (URISyntaxException ex) {
//给定的导入元素的location不是绝对路径
}
//给定的导入元素的location是绝对路径
if (absoluteLocation) {
try {
//使用资源读入器加载给定路径的Bean定义资源
int importCount = getReaderContext().getReader().loadBeanDefinitions(location, actualResources);
if (logger.isDebugEnabled()) {
logger.debug("Imported " + importCount + " bean definitions from URL location [" + location + "]");
}
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error(
"Failed to import bean definitions from URL location [" + location + "]", ele, ex);
}
}
else {
//给定的导入元素的location是相对路径
try {
int importCount;
//将给定导入元素的location封装为相对路径资源
Resource relativeResource = getReaderContext().getResource().createRelative(location);
//封装的相对路径资源存在
if (relativeResource.exists()) {
//使用资源读入器加载Bean定义资源
importCount = getReaderContext().getReader().loadBeanDefinitions(relativeResource);
actualResources.add(relativeResource);
}
//封装的相对路径资源不存在
else {
//获取Spring IoC容器资源读入器的基本路径
String baseLocation = getReaderContext().getResource().getURL().toString();
//根据Spring IoC容器资源读入器的基本路径加载给定导入
//路径的资源
importCount = getReaderContext().getReader().loadBeanDefinitions(
StringUtils.applyRelativePath(baseLocation, location), actualResources);
}
if (logger.isDebugEnabled()) {
logger.debug("Imported " + importCount + " bean definitions from relative location [" + location + "]");
}
}
catch (IOException ex) {
getReaderContext().error("Failed to resolve current resource location", ele, ex);
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to import bean definitions from relative location [" + location + "]",
ele, ex);
}
}
Resource[] actResArray = actualResources.toArray(new Resource[actualResources.size()]);
//在解析完<Import>元素之后，发送容器导入其他资源处理完成事件
getReaderContext().fireImportProcessed(location, actResArray, extractSource(ele));
}

//       Alias

//解析<Alias>别名元素，为Bean向Spring IoC容器注册别名
protected void processAliasRegistration(Element ele) {
//获取<Alias>别名元素中name的属性值
String name = ele.getAttribute(NAME_ATTRIBUTE);
//获取<Alias>别名元素中alias的属性值
String alias = ele.getAttribute(ALIAS_ATTRIBUTE);
boolean valid = true;
//<alias>别名元素的name属性值为空
if (!StringUtils.hasText(name)) {
getReaderContext().error("Name must not be empty", ele);
valid = false;
}
//<alias>别名元素的alias属性值为空
if (!StringUtils.hasText(alias)) {
getReaderContext().error("Alias must not be empty", ele);
valid = false;
}
if (valid) {
try {
//向容器的资源读入器注册别名
getReaderContext().getRegistry().registerAlias(name, alias);
}
catch (Exception ex) {
getReaderContext().error("Failed to register alias '" + alias +
"' for bean with name '" + name + "'", ele, ex);
}
//在解析完<Alias>元素之后，发送容器别名处理完成事件
getReaderContext().fireAliasRegistered(name, alias, extractSource(ele));
}
}

///////            解析Bean

//解析Bean定义资源Document对象的普通元素
protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
// BeanDefinitionHolder是对BeanDefinition的封装，即Bean定义的封装类
//对Document对象中<Bean>元素的解析由BeanDefinitionParserDelegate实现
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
//向Spring IoC容器注册解析得到的Bean定义，这是Bean定义向IoC容器注册的入口            BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
//在完成向Spring IoC容器注册解析得到的Bean定义之后，发送注册事件
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}

对于import 这个引入其他配置文件的标签的处理思路是:

先验证这个链接是否正确,然后定位这个资源,如果这个资源合法最后载入这一个资源,并发送处理完成事件

最重要的就是对于Bean的解析了调用这个方法开始解析: BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());

//	加载Bean 类型的Element

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}

加载类名,ID等主要的属性

下面进入BeanDefinitionParserDelegate类中的方法

//	加载过程
////解析Bean定义资源文件中的<Bean>元素，这个方法中主要处理<Bean>元素的id，name

public BeanDefinitionHolder parseBeanDefinitionElement(Element ele, BeanDefinition containingBean) {
String id = ele.getAttribute(ID_ATTRIBUTE);
String nameAttr = ele.getAttribute(NAME_ATTRIBUTE);

List aliases = new ArrayList();
if (StringUtils.hasLength(nameAttr)) {
String[] nameArr = StringUtils.tokenizeToStringArray(nameAttr, BEAN_NAME_DELIMITERS);
aliases.addAll(Arrays.asList(nameArr));
}

String beanName = id;
if (!StringUtils.hasText(beanName) && !aliases.isEmpty()) {
beanName = (String) aliases.remove(0);
if (logger.isDebugEnabled()) {
logger.debug("No XML 'id' specified - using '" + beanName +
"' as bean name and " + aliases + " as aliases");
}
}

if (containingBean == null) {

checkNameUniqueness(beanName, aliases, ele);
}

//		 //详细对<Bean>元素中配置的Bean定义进行解析的地方
AbstractBeanDefinition beanDefinition = parseBeanDefinitionElement(ele, beanName, containingBean);

if (beanDefinition != null) {
if (!StringUtils.hasText(beanName)) {
try {
if (containingBean != null) {
beanName = BeanDefinitionReaderUtils.generateBeanName(
beanDefinition, this.readerContext.getRegistry(), true);
}
else {
beanName = this.readerContext.generateBeanName(beanDefinition);
// Register an alias for the plain bean class name, if still possible,
// if the generator returned the class name plus a suffix.
// This is expected for Spring 1.2/2.0 backwards compatibility.
String beanClassName = beanDefinition.getBeanClassName();
if (beanClassName != null &&
beanName.startsWith(beanClassName) && beanName.length() > beanClassName.length() &&
!this.readerContext.getRegistry().isBeanNameInUse(beanClassName)) {
aliases.add(beanClassName);
}
}
if (logger.isDebugEnabled()) {
logger.debug("Neither XML 'id' nor 'name' specified - " +
"using generated bean name [" + beanName + "]");
}
}
catch (Exception ex) {
error(ex.getMessage(), ele);
return null;
}
}
String[] aliasesArray = StringUtils.toStringArray(aliases);
return new BeanDefinitionHolder(beanDefinition, beanName, aliasesArray);
}

return null;
}

加载完主要信息,开始加载其他Element标签的信息

/详细加载Bean中的其他Element

public AbstractBeanDefinition parseBeanDefinitionElement(
Element ele, String beanName, BeanDefinition containingBean) {

String className = null;
if (ele.hasAttribute(CLASS_ATTRIBUTE)) {
className = ele.getAttribute(CLASS_ATTRIBUTE).trim();
}
String parent = null;
if (ele.hasAttribute(PARENT_ATTRIBUTE)) {
parent = ele.getAttribute(PARENT_ATTRIBUTE);
}

try {
this.parseState.push(new BeanEntry(beanName));
//创建 BeanDefinition 根据 Class。并设置classLoader 和parent
AbstractBeanDefinition bd = BeanDefinitionReaderUtils.createBeanDefinition(
parent, className, this.readerContext.getBeanClassLoader());
//scope属性
if (ele.hasAttribute(SCOPE_ATTRIBUTE)) {
// Spring 2.x "scope" attribute
bd.setScope(ele.getAttribute(SCOPE_ATTRIBUTE));
if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
error("Specify either 'scope' or 'singleton', not both", ele);
}
}

//	SINGLETON
else if (ele.hasAttribute(SINGLETON_ATTRIBUTE)) {
// Spring 1.x "singleton" attribute
bd.setScope(TRUE_VALUE.equals(ele.getAttribute(SINGLETON_ATTRIBUTE)) ?
BeanDefinition.SCOPE_SINGLETON : BeanDefinition.SCOPE_PROTOTYPE);
}
else if (containingBean != null) {
// Take default from containing bean in case of an inner bean definition.
bd.setScope(containingBean.getScope());
}
//	ABSTRACT
if (ele.hasAttribute(ABSTRACT_ATTRIBUTE)) {
bd.setAbstract(TRUE_VALUE.equals(ele.getAttribute(ABSTRACT_ATTRIBUTE)));
}
//	lazyInit
String lazyInit = ele.getAttribute(LAZY_INIT_ATTRIBUTE);
if (DEFAULT_VALUE.equals(lazyInit) && bd.isSingleton()) {
// Just apply default to singletons, as lazy-init has no meaning for prototypes.
lazyInit = this.defaults.getLazyInit();
}
bd.setLazyInit(TRUE_VALUE.equals(lazyInit));
//	AUTOWIRE
String autowire = ele.getAttribute(AUTOWIRE_ATTRIBUTE);
bd.setAutowireMode(getAutowireMode(autowire));
//	DEPENDENCY
String dependencyCheck = ele.getAttribute(DEPENDENCY_CHECK_ATTRIBUTE);
bd.setDependencyCheck(getDependencyCheck(dependencyCheck));
//	DEPENDS
if (ele.hasAttribute(DEPENDS_ON_ATTRIBUTE)) {
String dependsOn = ele.getAttribute(DEPENDS_ON_ATTRIBUTE);
bd.setDependsOn(StringUtils.tokenizeToStringArray(dependsOn, BEAN_NAME_DELIMITERS));
}
//	AUTOWIRE_CANDIDATE
String autowireCandidate = ele.getAttribute(AUTOWIRE_CANDIDATE_ATTRIBUTE);

//	DEFAULT_VALUE
if ("".equals(autowireCandidate) || DEFAULT_VALUE.equals(autowireCandidate)) {
String candidatePattern = this.defaults.getAutowireCandidates();
if (candidatePattern != null) {
String[] patterns = StringUtils.commaDelimitedListToStringArray(candidatePattern);
bd.setAutowireCandidate(PatternMatchUtils.simpleMatch(patterns, beanName));
}
}
else {
bd.setAutowireCandidate(TRUE_VALUE.equals(autowireCandidate));
}

if (ele.hasAttribute(PRIMARY_ATTRIBUTE)) {
bd.setPrimary(TRUE_VALUE.equals(ele.getAttribute(PRIMARY_ATTRIBUTE)));
}
//	INIT_METHOD
if (ele.hasAttribute(INIT_METHOD_ATTRIBUTE)) {
String initMethodName = ele.getAttribute(INIT_METHOD_ATTRIBUTE);
if (!"".equals(initMethodName)) {
bd.setInitMethodName(initMethodName);
}
}
else {
if (this.defaults.getInitMethod() != null) {
bd.setInitMethodName(this.defaults.getInitMethod());
bd.setEnforceInitMethod(false);
}
}

if (ele.hasAttribute(DESTROY_METHOD_ATTRIBUTE)) {
String destroyMethodName = ele.getAttribute(DESTROY_METHOD_ATTRIBUTE);
if (!"".equals(destroyMethodName)) {
bd.setDestroyMethodName(destroyMethodName);
}
}
else {
if (this.defaults.getDestroyMethod() != null) {
bd.setDestroyMethodName(this.defaults.getDestroyMethod());
bd.setEnforceDestroyMethod(false);
}
}

if (ele.hasAttribute(FACTORY_METHOD_ATTRIBUTE)) {
bd.setFactoryMethodName(ele.getAttribute(FACTORY_METHOD_ATTRIBUTE));
}
if (ele.hasAttribute(FACTORY_BEAN_ATTRIBUTE)) {
bd.setFactoryBeanName(ele.getAttribute(FACTORY_BEAN_ATTRIBUTE));
}

bd.setDescription(DomUtils.getChildElementValueByTagName(ele, DESCRIPTION_ELEMENT));

parseMetaElements(ele, bd);
parseLookupOverrideSubElements(ele, bd.getMethodOverrides());
parseReplacedMethodSubElements(ele, bd.getMethodOverrides());
//	解析构造方法
parseConstructorArgElements(ele, bd);
//	property属性
parsePropertyElements(ele, bd);
parseQualifierElements(ele, bd);
//为当前解析的Bean设置所需的资源和依赖对象
bd.setResource(this.readerContext.getResource());
bd.setSource(extractSource(ele));

return bd;
}
catch (ClassNotFoundException ex) {
error("Bean class [" + className + "] not found", ele, ex);
}
catch (NoClassDefFoundError err) {
error("Class that bean class [" + className + "] depends on not found", ele, err);
}
catch (Throwable ex) {
error("Unexpected failure during bean definition parsing", ele, ex);
}
finally {
this.parseState.pop();
}

return null;
}

BeanDefinitionReaderUtils 里面加载了classLoader parent等属性

//BeanDefinitionReaderUtils

public static AbstractBeanDefinition createBeanDefinition(
String parentName, String className, ClassLoader classLoader) throws ClassNotFoundException {

GenericBeanDefinition bd = new GenericBeanDefinition();
bd.setParentName(parentName);
if (className != null) {
if (classLoader != null) {
bd.setBeanClass(ClassUtils.forName(className, classLoader));
}
else {
bd.setBeanClassName(className);
}
}
return bd;
}

下面就是解析构造函数的具体实现了

/**
* Parse constructor-arg sub-elements of the given bean element.
*/
public void parseConstructorArgElements(Element beanEle, BeanDefinition bd) {
NodeList nl = beanEle.getChildNodes();
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element && DomUtils.nodeNameEquals(node, CONSTRUCTOR_ARG_ELEMENT)) {
parseConstructorArgElement((Element) node, bd);
}
}
}

解析Property的实现

/**
* Parse property sub-elements of the given bean element.
*/
public void parsePropertyElements(Element beanEle, BeanDefinition bd) {
NodeList nl = beanEle.getChildNodes();
//遍历每一个节点
for (int i = 0; i < nl.getLength(); i++) {
Node node = nl.item(i);
if (node instanceof Element && DomUtils.nodeNameEquals(node, PROPERTY_ELEMENT)) {
//分别解析每一个property节点
parsePropertyElement((Element) node, bd);
}
}
}

对每个property节点分别解析

/**
* Parse a property element.
*/
public void parsePropertyElement(Element ele, BeanDefinition bd) {
String propertyName = ele.getAttribute(NAME_ATTRIBUTE);//获取名称
if (!StringUtils.hasLength(propertyName)) {
error("Tag 'property' must have a 'name' attribute", ele);
return;
}
this.parseState.push(new PropertyEntry(propertyName));//放入栈中
try {
if (bd.getPropertyValues().contains(propertyName)) {//如果有同名元素,不解析
error("Multiple 'property' definitions for property '" + propertyName + "'", ele);
return;
}
Object val = parsePropertyValue(ele, bd, propertyName);//val 为解析得到的值
PropertyValue pv = new PropertyValue(propertyName, val);//放入propertyValue中,
parseMetaElements(ele, pv);
pv.setSource(extractSource(ele));
bd.getPropertyValues().addPropertyValue(pv);<span style="font-family: Arial, Helvetica, sans-serif;">//设置到BeanDefinitionHolder中</span>

}
finally {
this.parseState.pop();
}
}

取得property元素的值,也许是个list或者其他的

/**
* Get the value of a property element. May be a list etc.
* Also used for constructor arguments, "propertyName" being null in this case.
*/
public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) {
String elementName = (propertyName != null) ?
"<property> element for property '" + propertyName + "'" :
"<constructor-arg> element";

// Should only have one child element: ref, value, list, etc.
NodeList nl = ele.getChildNodes();
Element subElement = null;
for (int i = 0; i < nl.getLength(); i++) {
if (nl.item(i) instanceof Element) {
Element candidateEle = (Element) nl.item(i);
if (DomUtils.nodeNameEquals(candidateEle, DESCRIPTION_ELEMENT) ||
DomUtils.nodeNameEquals(candidateEle, META_ELEMENT)) {
// Keep going: we don't use these values for now.
}
else {
// Child element is what we're looking for.
if (subElement != null) {
error(elementName + " must not contain more than one sub-element", ele);
}
else {
subElement = candidateEle;
}
}
}
}
<span style="white-space:pre">		</span>//不能同时拥有ref或者value属性
boolean hasRefAttribute = ele.hasAttribute(REF_ATTRIBUTE);
boolean hasValueAttribute = ele.hasAttribute(VALUE_ATTRIBUTE);
if ((hasRefAttribute && hasValueAttribute) ||
((hasRefAttribute || hasValueAttribute) && subElement != null)) {
error(elementName +
" is only allowed to contain either 'ref' attribute OR 'value' attribute OR sub-element", ele);
}
<span style="white-space:pre">		</span>//ref类型
if (hasRefAttribute) {
String refName = ele.getAttribute(REF_ATTRIBUTE);//获取元素名字
if (!StringUtils.hasText(refName)) {
error(elementName + " contains empty 'ref' attribute", ele);
}
RuntimeBeanReference ref = new RuntimeBeanReference(refName);//创建RuntimeBeanReference  封装ref信息
ref.setSource(extractSource(ele));<span style="font-family: Arial, Helvetica, sans-serif;">//是一个指向运行时所依赖对象的引用 </span>
return ref;
}
else if (hasValueAttribute) {//value类型
TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE));
valueHolder.setSource(extractSource(ele));
return valueHolder;
}//如果有子属性,继续解析 例如List Map 等
else if (subElement != null) {
return parsePropertySubElement(subElement, bd);
}
else {
// Neither child element nor "ref" or "value" attribute found.
error(elementName + " must specify a ref or value", ele);
return null;
}
}

通过对上述源码的分析，我们可以了解在Spring配置文件中，<Bean>元素中<property>元素的相关配置是如何处理的：

a. ref被封装为指向依赖对象一个引用。

b.value配置都会封装成一个字符串类型的对象。

c.ref和value都通过“解析的数据类型属性值.setSource(extractSource(ele));”方法将属性值/引用与所引用的属性关联起来。

在方法的最后对于<property>元素的子元素通过parsePropertySubElement 方法解析，我们继续分析该方法的源码，了解其解析过程。

6.解析<property>元素的子元素：

在BeanDefinitionParserDelegate类中的parsePropertySubElement方法对<property>中的子元素解析，源码如下：

//解析<property>元素中ref,value或者集合等子元素
public Object parsePropertySubElement(Element ele, BeanDefinition bd, String defaultValueType) {
//如果<property>没有使用Spring默认的命名空间，则使用用户自定义的规则解析//内嵌元素
if (!isDefaultNamespace(ele)) {
return parseNestedCustomElement(ele, bd);
}
//如果子元素是bean，则使用解析<Bean>元素的方法解析
else if (nodeNameEquals(ele, BEAN_ELEMENT)) {
BeanDefinitionHolder nestedBd = parseBeanDefinitionElement(ele, bd);
if (nestedBd != null) {
nestedBd = decorateBeanDefinitionIfRequired(ele, nestedBd, bd);
}
return nestedBd;
}
//如果子元素是ref，ref中只能有以下3个属性：bean、local、parent
else if (nodeNameEquals(ele, REF_ELEMENT)) {
//获取<property>元素中的bean属性值，引用其他解析的Bean的名称
//可以不再同一个Spring配置文件中，具体请参考Spring对ref的配置规则
String refName = ele.getAttribute(BEAN_REF_ATTRIBUTE);
boolean toParent = false;
if (!StringUtils.hasLength(refName)) {
//获取<property>元素中的local属性值，引用同一个Xml文件中配置
//的Bean的id，local和ref不同，local只能引用同一个配置文件中的Bean
refName = ele.getAttribute(LOCAL_REF_ATTRIBUTE);
if (!StringUtils.hasLength(refName)) {
//获取<property>元素中parent属性值，引用父级容器中的Bean
refName = ele.getAttribute(PARENT_REF_ATTRIBUTE);
toParent = true;
if (!StringUtils.hasLength(refName)) {
error("'bean', 'local' or 'parent' is required for <ref> element", ele);
return null;
}
}
}
//没有配置ref的目标属性值
if (!StringUtils.hasText(refName)) {
error("<ref> element contains empty target attribute", ele);
return null;
}
//创建ref类型数据，指向被引用的对象
RuntimeBeanReference ref = new RuntimeBeanReference(refName, toParent);
//设置引用类型值是被当前子元素所引用
ref.setSource(extractSource(ele));
return ref;
}
//如果子元素是<idref>，使用解析ref元素的方法解析
else if (nodeNameEquals(ele, IDREF_ELEMENT)) {
return parseIdRefElement(ele);
}
//如果子元素是<value>，使用解析value元素的方法解析
else if (nodeNameEquals(ele, VALUE_ELEMENT)) {
return parseValueElement(ele, defaultValueType);
}
//如果子元素是null，为<property>设置一个封装null值的字符串数据
else if (nodeNameEquals(ele, NULL_ELEMENT)) {
TypedStringValue nullHolder = new TypedStringValue(null);
nullHolder.setSource(extractSource(ele));
return nullHolder;
}
//如果子元素是<array>，使用解析array集合子元素的方法解析
else if (nodeNameEquals(ele, ARRAY_ELEMENT)) {
return parseArrayElement(ele, bd);
}
//如果子元素是<list>，使用解析list集合子元素的方法解析
else if (nodeNameEquals(ele, LIST_ELEMENT)) {
return parseListElement(ele, bd);
}
//如果子元素是<set>，使用解析set集合子元素的方法解析
else if (nodeNameEquals(ele, SET_ELEMENT)) {
return parseSetElement(ele, bd);
}
//如果子元素是<map>，使用解析map集合子元素的方法解析
else if (nodeNameEquals(ele, MAP_ELEMENT)) {
return parseMapElement(ele, bd);
}
//如果子元素是<props>，使用解析props集合子元素的方法解析
else if (nodeNameEquals(ele, PROPS_ELEMENT)) {
return parsePropsElement(ele);
}
//既不是ref，又不是value，也不是集合，则子元素配置错误，返回null
else {
error("Unknown property sub-element: [" + ele.getNodeName() + "]", ele);
return null;
}
}

解析List

//解析<list>集合子元素
public List parseListElement(Element collectionEle, BeanDefinition bd) {
//获取<list>元素中的value-type属性，即获取集合元素的数据类型
String defaultElementType = collectionEle.getAttribute(VALUE_TYPE_ATTRIBUTE);
//获取<list>集合元素中的所有子节点
NodeList nl = collectionEle.getChildNodes();
//Spring中将List封装为ManagedList
ManagedList<Object> target = new ManagedList<Object>(nl.getLength());
target.setSource(extractSource(collectionEle));
//设置集合目标数据类型
target.setElementTypeName(defaultElementType);
target.setMergeEnabled(parseMergeAttribute(collectionEle));
//具体的<list>元素解析
parseCollectionElements(nl, target, bd, defaultElementType);
return target;
}
//具体解析<list>集合元素，<array>、<list>和<set>都使用该方法解析
protected void parseCollectionElements(
NodeList elementNodes, Collection<Object> target, BeanDefinition bd, String defaultElementType) {
//遍历集合所有节点
for (int i = 0; i < elementNodes.getLength(); i++) {
Node node = elementNodes.item(i);
//节点不是description节点
if (node instanceof Element && !nodeNameEquals(node, DESCRIPTION_ELEMENT)) {
//将解析的元素加入集合中，递归调用下一个子元素
target.add(parsePropertySubElement((Element) node, bd, defaultElementType));
}
}
}

经过对Spring Bean定义资源文件转换的Document对象中的元素层层解析，Spring IoC现在已经将XML形式定义的Bean定义资源文件转换为Spring IoC所识别的数据结构——BeanDefinition，它是Bean定义资源文件中配置的POJO对象在Spring IoC容器中的映射，我们可以通过AbstractBeanDefinition为入口，荣IoC容器进行索引、查询和操作。

通过Spring IoC容器对Bean定义资源的解析后，IoC容器大致完成了管理Bean对象的准备工作，即初始化过程，但是最为重要的依赖注入还没有发生，现在在IoC容器中BeanDefinition存储的只是一些静态信息，接下来需要向容器注册Bean定义信息才能全部完成IoC容器的初始化过程。

注册的过程就是将处理好的BeanDefinition加入到 BeanDefinitionMap中

处理注册的代码在DefaultListableBeanFactory中

public void registerBeanDefinition(String beanName, BeanDefinition beanDefinition)
throws BeanDefinitionStoreException {

Assert.hasText(beanName, "'beanName' must not be empty");
Assert.notNull(beanDefinition, "BeanDefinition must not be null");

if (beanDefinition instanceof AbstractBeanDefinition) {
try {
((AbstractBeanDefinition) beanDefinition).validate();
}
catch (BeanDefinitionValidationException ex) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Validation of bean definition failed", ex);
}
}
//保持数据一致性
synchronized (this.beanDefinitionMap) {
Object oldBeanDefinition = this.beanDefinitionMap.get(beanName);
if (oldBeanDefinition != null) {
if (!this.allowBeanDefinitionOverriding) {
throw new BeanDefinitionStoreException(beanDefinition.getResourceDescription(), beanName,
"Cannot register bean definition [" + beanDefinition + "] for bean '" + beanName +
"': There is already [" + oldBeanDefinition + "] bound.");
}
else {
if (this.logger.isInfoEnabled()) {
this.logger.info("Overriding bean definition for bean '" + beanName +
"': replacing [" + oldBeanDefinition + "] with [" + beanDefinition + "]");
}
}
}
else {
this.beanDefinitionNames.add(beanName);
this.frozenBeanDefinitionNames = null;
}
this.beanDefinitionMap.put(beanName, beanDefinition);

resetBeanDefinition(beanName);
}
}

</pre><div style="top:2271px"><p>而载入和注册都在这一个函数中,DefaultBeanDefinitionDocumentReader类的方法:<pre name="code" class="java">protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {
BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);
if (bdHolder != null) {
bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);
try {
// Register the final decorated instance.
BeanDefinitionReaderUtils.registerBeanDefinition(bdHolder, getReaderContext().getRegistry());
}
catch (BeanDefinitionStoreException ex) {
getReaderContext().error("Failed to register bean definition with name '" +
bdHolder.getBeanName() + "'", ele, ex);
}
// Send registration event.
getReaderContext().fireComponentRegistered(new BeanComponentDefinition(bdHolder));
}
}