Spring 源码阅读 02：ApplicationContext 初始化 Spring 容器

ApplicationContextcontext=newClassPathXmlApplicationContext("beans.xml");
Useruser=context.getBean("user", User.class);
user.sayHello();

publicClassPathXmlApplicationContext(StringconfigLocation) throwsBeansException {
this(newString[] {configLocation}, true, null);
}

publicClassPathXmlApplicationContext(
String[] configLocations, booleanrefresh, @NullableApplicationContextparent)
throwsBeansException {
super(parent);
setConfigLocations(configLocations);
if (refresh) {
refresh();
   }
}

publicAbstractApplicationContext(@NullableApplicationContextparent) {
this();
setParent(parent);
}

publicAbstractApplicationContext() {
this.resourcePatternResolver=getResourcePatternResolver();
}

protectedResourcePatternResolvergetResourcePatternResolver() {
returnnewPathMatchingResourcePatternResolver(this);
}

publicvoidsetParent(@NullableApplicationContextparent) {
this.parent=parent;
if (parent!=null) {
EnvironmentparentEnvironment=parent.getEnvironment();
if (parentEnvironmentinstanceofConfigurableEnvironment) {
getEnvironment().merge((ConfigurableEnvironment) parentEnvironment);
      }
   }
}

publicvoidsetConfigLocations(@NullableString... locations) {
if (locations!=null) {
Assert.noNullElements(locations, "Config locations must not be null");
this.configLocations=newString[locations.length];
for (inti=0; i<locations.length; i++) {
this.configLocations[i] =resolvePath(locations[i]).trim();
      }
   }
else {
this.configLocations=null;
   }
}

protectedStringresolvePath(Stringpath) {
returngetEnvironment().resolveRequiredPlaceholders(path);
}

@Overridepublicvoidrefresh() throwsBeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.// 初始化上下文的信息prepareRefresh();
// Tell the subclass to refresh the internal bean factory.// 这里会调用模版方法，通过子类的实现，初始化 BeanFactory 并解析 XML 配置ConfigurableListableBeanFactorybeanFactory=obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.// 对 BeanFactory 进行初始配置prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.// 这里默认是一个空的模版方法，子类可以在此处实现逻辑postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.// 执行 BeanFactory 的后处理器invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.// 注册 Bean 的后处理器registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.// 初始化消息源initMessageSource();
// Initialize event multicaster for this context.// 初始化时间广播器initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.// 这里也是一个空的模版方法，子类可以在此处实现逻辑，在容器中的单例 Bean 初始化之前，来初始化一些特殊的 BeanonRefresh();
// Check for listener beans and register them.// 注册化监听器registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.// 完成 BeanFactory 初始化，实例化所有非延迟加载的单例 BeanfinishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.// 初始化结束，广播相应的事件finishRefresh();
      }
catch (BeansExceptionex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - "+"cancelling refresh attempt: "+ex);
         }
// Destroy already created singletons to avoid dangling resources.destroyBeans();
// Reset 'active' flag.cancelRefresh(ex);
// Propagate exception to caller.throwex;
      }
finally {
// Reset common introspection caches in Spring's core, since we// might not ever need metadata for singleton beans anymore...resetCommonCaches();
      }
   }
}