Spring 源碼（十）Spring Aware自動裝配原理

Spring Aware自動裝配有兩種實作方式：

1. 在初始化Bean的​

   ​initializeBean​

   ​​方法中執行​

   ​invokeAwareMethods​

   ​方法
2. 通後置處理器​

   ​ApplicationContextAwareProcessor​

   ​​來實作的，它實作了​

   ​BeanPostProcessor​

   ​接口

invokeAwareMethods

我們在初始化​

​Bean​

​​的時候，為了保證一部分​

​Aware​

​​必須在後置處理器​

​postProcessBeforeInitialization​

​​方法之前執行，是以在​

​Bean​

​​初始化之前直接調用了​

​invokeAwareMethods​

​方法。源碼如下：

private void invokeAwareMethods(final String beanName, final Object bean) {
  if (bean instanceof Aware) {
    if (bean instanceof BeanNameAware) {
      ((BeanNameAware) bean).setBeanName(beanName);
    }
    if (bean instanceof BeanClassLoaderAware) {
      ((BeanClassLoaderAware) bean).setBeanClassLoader(getBeanClassLoader());
    }
    if (bean instanceof BeanFactoryAware) {
      ((BeanFactoryAware) bean).setBeanFactory(AbstractAutowireCapableBeanFactory.this);
    }
  }
}      

ApplicationContextAwareProcessor

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);
    }
    if (bean instanceof ApplicationContextAware) {
      ((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
    }
  }
}      

總結

1. 判斷是否實作了​

   ​Aware​

   ​接口
2. 判斷具體實作了那個​

   ​Aware​

   ​接口
3. 直接調用​

   ​XxxAware​

   ​​接口的特有方法實作​

   ​XxxAware​

   ​的自動裝配