Spring之ApplicationContextAware使用详解

Spring定义的类实现ApplicationContextAware接口会自动的将应用程序上下文加入，首先我们看下具体的实现示例；

示例代码

• package com.yaomy.security.oauth2.filter;import org.springframework.beans.BeansException;
  import org.springframework.context.ApplicationContext;
  import org.springframework.context.ApplicationContextAware;
  import org.springframework.stereotype.Component;/*** @Description: Description* @ProjectName: spring-parent* @Package: com.yaomy.security.oauth2.filter.BeanUtils* @Date: 2019/8/1 10:58* @Version: 1.0*/
  @Component
  public class BeanUtils implements ApplicationContextAware {private ApplicationContext applicationContext;@Overridepublic void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.applicationContext = applicationContext;}
  }
  

ApplicationContextAware的使用方式很简单，只要实现接口重写方法就可以，下面我们看下应用程序是如何初始化的

• AbstractApplicationContext类是Spring容器应用上下文的一个抽象父类，我们看下里面的prepareBeanFactory方法

•   protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {beanFactory.setBeanClassLoader(this.getClassLoader());beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, this.getEnvironment()));//添加ApplicationContextAware的处理器beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));beanFactory.ignoreDependencyInterface(EnvironmentAware.class);beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);beanFactory.ignoreDependencyInterface(MessageSourceAware.class);beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);beanFactory.registerResolvableDependency(ResourceLoader.class, this);beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);beanFactory.registerResolvableDependency(ApplicationContext.class, this);beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));if (beanFactory.containsBean("loadTimeWeaver")) {beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));}if (!beanFactory.containsLocalBean("environment")) {beanFactory.registerSingleton("environment", this.getEnvironment());}if (!beanFactory.containsLocalBean("systemProperties")) {beanFactory.registerSingleton("systemProperties", this.getEnvironment().getSystemProperties());}if (!beanFactory.containsLocalBean("systemEnvironment")) {beanFactory.registerSingleton("systemEnvironment", this.getEnvironment().getSystemEnvironment());}}
  

进入ApplicationContextAwareProcessor处理器类查看代码

•     @Nullablepublic Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {AccessControlContext acc = null;if (System.getSecurityManager() != null && (bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware || bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware || bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware)) {acc = this.applicationContext.getBeanFactory().getAccessControlContext();}if (acc != null) {AccessController.doPrivileged(() -> {//调用ApplicationContextAware 初始化方法this.invokeAwareInterfaces(bean);return null;}, acc);} else {this.invokeAwareInterfaces(bean);}return bean;}//具体实现private void invokeAwareInterfaces(Object bean) {if (bean instanceof Aware) {if (bean instanceof EnvironmentAware) {((EnvironmentAware)bean).setEnvironment(this.applicationContext.getEnvironment());}if (bean instanceof EmbeddedValueResolverAware) {((EmbeddedValueResolverAware)bean).setEmbeddedValueResolver(this.embeddedValueResolver);}if (bean instanceof ResourceLoaderAware) {((ResourceLoaderAware)bean).setResourceLoader(this.applicationContext);}if (bean instanceof ApplicationEventPublisherAware) {((ApplicationEventPublisherAware)bean).setApplicationEventPublisher(this.applicationContext);}if (bean instanceof MessageSourceAware) {((MessageSourceAware)bean).setMessageSource(this.applicationContext);}//初始化if (bean instanceof ApplicationContextAware) {((ApplicationContextAware)bean).setApplicationContext(this.applicationContext);}}}
  

• 通过上面的代码可以很清楚的了解到ApplicationContextAware实现类在应用启动的时候就会初始化。。。