Spring初始化

一.概述

1. XmlWebApplicationContext在org.springframework.web.context.ContextLoader # createWebApplicationContext（）实例化后，在

org.springframework.web.context.ContextLoader #  configureAndRefreshWebApplicationContext()配置并刷新上下文XmlWebApplicationContext

2. 由上下文抽象类org.springframework.context.support.AbstractApplicationContext # refresh()方法实现刷新方法：会加载spring xml配置，属性文件或关系数据库模式等信息

二.刷新

1.上下文刷新的整个流程

org.springframework.context.support.AbstractApplicationContext # 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;}}}

2.主要看看方法：获取bean工厂

ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory()

3.返回刷新的bean工厂

org.springframework.context.support.AbstractApplicationContext # obtainFreshBeanFactory() 

/** * 返回子类刷新的bean工厂 * @return the fresh BeanFactory instance */protected ConfigurableListableBeanFactory obtainFreshBeanFactory() {// 子类实现refreshBeanFactory();// 获取子类实现的bean工厂ConfigurableListableBeanFactory beanFactory = getBeanFactory();if (logger.isDebugEnabled()) {logger.debug("Bean factory for " + getDisplayName() + ": " + beanFactory);}return beanFactory;}/** * 子类必须实现此方法来执行实际的配置加载。 * 这个方法必须在任何其他初始化工作之前由org.springframework.context.support.AbstractApplicationContext # refresh()调用 * * 子类将创建一个新的bean工厂并持有它的引用，或者返回一个它持有的单例bean工厂实例 * 返回一个持有的单例bean工厂实例情况下，如果多次刷新上下文，它通常抛出IllegalStateException异常 * @throws BeansException if initialization of the bean factory failed * @throws IllegalStateException if already initialized and multiple refresh attempts are not supported */protected abstract void refreshBeanFactory() throws BeansException, IllegalStateException;/** * 子类必须在这里返回它们的内部bean工厂。 他们应该有效地实现查找，以便可以重复调用，而不会造成性能损失。 *  * 注意：在返回内部bean工厂之前，子类应该检查上下文是否是active的。 一旦上下文已经关闭，内部bean工厂一般应被视为不可用 */public abstract ConfigurableListableBeanFactory getBeanFactory() throws IllegalStateException;

三.子类内部实现bean工厂

类org.springframework.context.support.AbstractApplicationContext 的子类org.springframework.context.support.AbstractRefreshableApplicationContext实现了父类的方法refreshBeanFactory()，执行配置文件的加载

1.如果当前上下文持有一个已经刷新过的bean工厂，需要先销毁此上下文所管理的所有的bean,再关闭bean工厂

2.创建一个bean工厂：org.springframework.beans.factory.support.DefaultListableBeanFactory

3.重点：加载xml配置文件中的bean,详见：四.加载xml中bean

/** * 此实现对该上下文的底层bean工厂执行实际刷新，关闭以前的bean工厂（如果有），并为上下文生命周期的下一阶段初始化一个新的bean工厂。 * This implementation performs an actual refresh of this context's underlying * bean factory, shutting down the previous bean factory (if any) and * initializing a fresh bean factory for the next phase of the context's lifecycle. */@Overrideprotected final void refreshBeanFactory() throws BeansException {// 如果当前持有一个已刷新的bean工厂if (hasBeanFactory()) {// 销毁此上下文管理的所有beandestroyBeans();// 关闭bean工厂closeBeanFactory();}try {// 创建一个bean工厂DefaultListableBeanFactoryDefaultListableBeanFactory beanFactory = createBeanFactory();// 将上下文的id作为bean工厂的序列化id,如org.springframework.web.context.WebApplicationContext:/bibeanFactory.setSerializationId(getId());// 自定义此上下文使用的内部bean工厂customizeBeanFactory(beanFactory);// 重点：加载xml配置文件中的beanloadBeanDefinitions(beanFactory);synchronized (this.beanFactoryMonitor) {this.beanFactory = beanFactory;}} catch (IOException ex) {throw new ApplicationContextException("I/O error parsing bean definition source for " + getDisplayName(), ex);}}/** * 为此上下文创建一个内部bean工厂 */protected DefaultListableBeanFactory createBeanFactory() {/** * 1.如果上下文为根：XmlWebApplicationContext * 2.所以getInternalParentBeanFactory()返回null,即此上下文的bean工厂的父工厂为null，为根工厂 * 3.用给定的父工厂创建一个新的bean工厂DefaultListableBeanFactory */return new DefaultListableBeanFactory(getInternalParentBeanFactory());}/** * 父类方法：org.springframework.context.support.AbstractApplicationContext * 如果当前上下文为XmlWebApplicationContext * XmlWebApplicationContext的父上下文为null, 所以此方法返回null */protected BeanFactory getInternalParentBeanFactory() {return (getParent() instanceof ConfigurableApplicationContext) ?((ConfigurableApplicationContext) getParent()).getBeanFactory() : getParent();}/** * 确定此上下文当前是否持有一个bean工厂，即至少已刷新一次，但尚未关闭。 */protected final boolean hasBeanFactory() {synchronized (this.beanFactoryMonitor) {return (this.beanFactory != null);}}// 父类方法：org.springframework.context.support.AbstractApplicationContext protected void destroyBeans() {getBeanFactory().destroySingletons();}// 实现父类方法：org.springframework.context.support.AbstractApplicationContext@Overrideprotected final void closeBeanFactory() {synchronized (this.beanFactoryMonitor) {this.beanFactory.setSerializationId(null);this.beanFactory = null;}}

四.加载xml中bean

1.父类加载bean定义的方法：org.springframework.context.support.AbstractRefreshableApplicationContext

/** * 通常委托一个或多个bean定义reader，将bean加载到所给的bean工厂beanFactory中 * @param beanFactory the bean factory to load bean definitions into */protected abstract void loadBeanDefinitions(DefaultListableBeanFactory beanFactory)throws BeansException, IOException;

2.子类XmlWebApplicationContext实现了加载bean的方法：org.springframework.context.support.XmlWebApplicationContext

/** * 通过XmlBeanDefinitionReader加载bean定义 * @see org.springframework.beans.factory.xml.XmlBeanDefinitionReader */@Overrideprotected void loadBeanDefinitions(DefaultListableBeanFactory beanFactory) throws BeansException, 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.setEnvironment(this.getEnvironment());beanDefinitionReader.setResourceLoader(this);beanDefinitionReader.setEntityResolver(new ResourceEntityResolver(this));//A: Allow a subclass to provide custom initialization of the reader,then proceed with actually loading the bean definitions.initBeanDefinitionReader(beanDefinitionReader);loadBeanDefinitions(beanDefinitionReader);}/** * A: 初始化用于加载此上下文bean定义的XmlBeanDefinitionReader * 默认实现为空，可以被子类覆盖 * @param beanDefinitionReader the bean definition reader used by this context */protected void initBeanDefinitionReader(XmlBeanDefinitionReader beanDefinitionReader) {}/** * 使用给定的XmlBeanDefinitionReader加载bean定义。 * 可能存在多个xml配置文件 */protected void loadBeanDefinitions(XmlBeanDefinitionReader reader) throws IOException {/** * 返回此Web应用程序上下文的配置位置，如果未指定，则返回null。 * 返回一个数组：如[/WEB-INF/spring/applicationContext.xml] */ String[] configLocations = getConfigLocations();if (configLocations != null) {for (String configLocation : configLocations) {// 由XmlBeanDefinitionReader加载bean定义reader.loadBeanDefinitions(configLocation);}}}

五.下一篇

org.springframework.beans.factory.xml.XmlBeanDefinitionReader的父类方法loadBeanDefinitions（） 会加载bean定义

详情请看下一篇： Spring初始化 - XmlBeanDefinitionReader