ioc容器里面的对象分两种，一种是用户自定义对象，一种是容器对象
Aware 接口可以理解为用来获取某些容器对象的方法
获取容器对象肯定是为了想利用容器对象的能力/服务
通过实现某种类型的Aware 来将自定义对象与容器"攀上亲"
例如一个普通的Bean对象，需要用到BeanFactory，可以这样做
public class MyAware implements BeanFactoryAware {
BeanFactory beanFactory;
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
this.beanFactory = beanFactory;
}
}
实现BeanFactoryAware，重写setBeanFactory方法即可
Spring是怎么做到的呢？
其实是在初始化自定义类的时候，会调动ApplicationContextAwareProcessor类中的postProcessBeforeInitialization方法
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!(bean instanceof EnvironmentAware || bean instanceof EmbeddedValueResolverAware ||
bean instanceof ResourceLoaderAware || bean instanceof ApplicationEventPublisherAware ||
bean instanceof MessageSourceAware || bean instanceof ApplicationContextAware ||
bean instanceof ApplicationStartupAware)) {
return bean;
}
invokeAwareInterfaces(bean);
return bean;
}
这个方法会判断当前bean是否是EnvironmentAware、EmbeddedValueResolverAware、ResourceLoaderAware、ApplicationEventPublisherAware、MessageSourceAware、ApplicationContextAware、ApplicationStartupAware中的任意一个
如果是则执行invokeAwareInterfaces方法进行相应的处理
private void invokeAwareInterfaces(Object bean) {
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 ApplicationStartupAware) {
((ApplicationStartupAware) bean).setApplicationStartup(this.applicationContext.getApplicationStartup());
}
if (bean instanceof ApplicationContextAware) {
((ApplicationContextAware) bean).setApplicationContext(this.applicationContext);
}
}
将相应的对象set进自定义对象
然后自定义对象就可以使用这些容器对象的能力了
spring内部也经常可见这种用法
