Spring IOC核心源码学习

<bean id="XiaoWang" class="com.springstudy.talentshow.SuperInstrumentalist">     <property name="instruments">         <list>             <ref bean="piano"/>             <ref bean="saxophone"/>         </list>     </property> </bean>

加载时需要读取、解析、注册bean，这个过程具体的调用栈如下所示：

保存配置位置，并刷新

在调用ClassPathXmlApplicationContext后，先会将配置位置信息保存到configLocations，供后面解析使用，之后，会调用

的refresh方法进行刷新：

public ClassPathXmlApplicationContext(String[] configLocations, boolean refresh,          ApplicationContext parent) throws BeansException {      super(parent);     // 保存位置信息，比如`com/springstudy/talentshow/talent-show.xml`     setConfigLocations(configLocations);     if (refresh) {         // 刷新         refresh();     } }  public void refresh() throws BeansException, IllegalStateException {     synchronized (this.startupShutdownMonitor) {         // Prepare this context for refreshing.         prepareRefresh();         // Tell the subclass to refresh the internal bean factory.         ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();         // Prepare the bean factory for use in this context.         prepareBeanFactory(beanFactory);         try {             // Allows post-processing of the bean factory in context subclasses.             postProcessBeanFactory(beanFactory);             // Invoke factory processors registered as beans in the context.             invokeBeanFactoryPostProcessors(beanFactory);             // Register bean processors that intercept bean creation.             registerBeanPostProcessors(beanFactory);             // Initialize message source for this context.             initMessageSource();             // Initialize event multicaster for this context.             initApplicationEventMulticaster();             // Initialize other special beans in specific context subclasses.             onRefresh();             // Check for listener beans and register them.             registerListeners();             // Instantiate all remaining (non-lazy-init) singletons.             finishBeanFactoryInitialization(beanFactory);             // Last step: publish corresponding event.             finishRefresh();         }         catch (BeansException ex) {             // Destroy already created singletons to avoid dangling resources.             destroyBeans();             // Reset 'active' flag.             cancelRefresh(ex);             // Propagate exception to caller.             throw ex;         }     } }

protected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)      throws BeansException, IOException {     // Create a new XmlBeanDefinitionReader for the given BeanFactory.     XmlBeanDefinitionReader beanDefinitionReader = new XmlBeanDefinitionReader(beanFactory);     // ... ...     // Allow a subclass to provide custom initialization of the reader,     // then proceed with actually loading the bean definitions.     initBeanDefinitionReader(beanDefinitionReader);     loadBeanDefinitions(beanDefinitionReader); }

public int loadBeanDefinitions(String location, Set<Resource> actualResources)      throws BeanDefinitionStoreException {     // ... ...     // 通过Location来读取Resource     Resource[] resources = ((ResourcePatternResolver) resourceLoader).getResources(location);     int loadCount = loadBeanDefinitions(resources);     // ... ... }  public int loadBeanDefinitions(Resource... resources) throws BeanDefinitionStoreException {     Assert.notNull(resources, "Resource array must not be null");     int counter = 0;     for (Resource resource : resources) {         // 载入每一个resource         counter += loadBeanDefinitions(resource);     }     return counter; }

protected void parseBeanDefinitions(Element root, BeanDefinitionParserDelegate delegate) {     // ... ...     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)) {                 // 处理每个xml中的元素，可能是import、alias、bean                 parseDefaultElement(ele, delegate);             }             else {                 delegate.parseCustomElement(ele);             }         }     }     // ... ... }

protected void processBeanDefinition(Element ele, BeanDefinitionParserDelegate delegate) {  // 解析  BeanDefinitionHolder bdHolder = delegate.parseBeanDefinitionElement(ele);  if (bdHolder != null) {   bdHolder = delegate.decorateBeanDefinitionIfRequired(ele, bdHolder);   try {    // 注册    // 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));  } }

public AbstractBeanDefinition parseBeanDefinitionElement(         Element ele, String beanName, BeanDefinition containingBean) {      // ... ...     // 创建beandefinition     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());     // 处理“Constructor”     parseConstructorArgElements(ele, bd);     // 处理“Preperty”     parsePropertyElements(ele, bd);     parseQualifierElements(ele, bd);     // ... ... }

public Object parsePropertyValue(Element ele, BeanDefinition bd, String propertyName) {     String elementName = (propertyName != null) ?                     "<property> element for property '" + propertyName + "'" :                     "<constructor-arg> element";      // ... ...     if (hasRefAttribute) {     // 处理引用         String refName = ele.getAttribute(REF_ATTRIBUTE);         if (!StringUtils.hasText(refName)) {             error(elementName + " contains empty 'ref' attribute", ele);         }         RuntimeBeanReference ref = new RuntimeBeanReference(refName);         ref.setSource(extractSource(ele));         return ref;     }     else if (hasValueAttribute) {     // 处理值         TypedStringValue valueHolder = new TypedStringValue(ele.getAttribute(VALUE_ATTRIBUTE));         valueHolder.setSource(extractSource(ele));         return valueHolder;     }     else if (subElement != null) {     // 处理子类型（比如list、map等）         return parsePropertySubElement(subElement, bd);     }     // ... ... }

当完成初始化IOC容器后，如果bean没有设置lazy-init(延迟加载)属性，那么bean的实例就会在初始化IOC完成之后，及时地进行初始化。初始化时会先建立实例，然后根据配置利用反射对实例进行进一步操作，具体流程如下所示：

创建bean的实例

创建bean的实例过程函数调用栈如下所示：

注入bean的属性

注入bean的属性过程函数调用栈如下所示：

protected Object doCreateBean(final String beanName, final RootBeanDefinition mbd,          final Object[] args) {     // Instantiate the bean.     BeanWrapper instanceWrapper = null;     if (mbd.isSingleton()) {         instanceWrapper = this.factoryBeanInstanceCache.remove(beanName);     }     if (instanceWrapper == null) {         // 创建bean的实例         instanceWrapper = createBeanInstance(beanName, mbd, args);     }      // ... ...      // Initialize the bean instance.     Object exposedObject = bean;     try {         // 初始化bean的实例，如注入属性         populateBean(beanName, mbd, instanceWrapper);         if (exposedObject != null) {             exposedObject = initializeBean(beanName, exposedObject, mbd);         }     }      // ... ... }