一、Spring Aware接口介绍
spring中提供了一些以Aware结尾的接口：
实现这些接口的类在被实例化后可以获得对应的系统内部对象，比如实现BeanFactoryAware接口可以获得BeanFactory对象。
二、Spring Aware接口使用举例
以获得BeanFactory和ApplicationContext为例举例说明Aware接口的使用：
public class School implements ApplicationContextAware, BeanFactoryAware {
@Override
public void setBeanFactory(BeanFactory beanFactory) throws BeansException {
System.out.println("======" + beanFactory);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
System.out.println("======" + applicationContext);
}}
实现Aware接口后会要求实现对应的setter方法。
三、Spring Aware接口原理
这个功能也是基于BeanPostProcessor来实现的，搜索*AwareProcessor都是来实现不同Aware注入的，以ApplicationContextAwareProcessor为例说明：
class ApplicationContextAwareProcessor implements BeanPostProcessor {
private final ConfigurableApplicationContext applicationContext;
/**
* Create a new ApplicationContextAwareProcessor for the given context.
*/
public ApplicationContextAwareProcessor(ConfigurableApplicationContext applicationContext) {
this.applicationContext = applicationContext;
}
@Override
public Object postProcessBeforeInitialization(final Object bean, String beanName) throws BeansException {
AccessControlContext acc = null;
//做一些校验,这里不关注
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(new PrivilegedAction
@Override
public Object run() {
invokeAwareInterfaces(bean);
return null;
}
}, acc);
} else {
invokeAwareInterfaces(bean);
}
return bean;
}
// 这里是核心逻辑
private void invokeAwareInterfaces(Object bean) {
if (bean instanceof Aware) {
//实现了对应的Aware就调用对应的setter方法
if (bean instanceof EnvironmentAware) {
((EnvironmentAware) bean).setEnvironment(this.applicationContext.getEnvironment());
}
if (bean instanceof EmbeddedValueResolverAware) {
((EmbeddedValueResolverAware) bean)
.setEmbeddedValueResolver(new EmbeddedValueResolver(this.applicationContext.getBeanFactory()));
}
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);
}}}}
实现逻辑很简单，就判断对象实现了什么接口就调用对应的setter方法，更重要的是看postProcessBeforeInitialization是在什么地方被调用的，反推方法定位到doCreateBean流程中，在填充对象完毕和调用初始化方法之间调用了postProcessBeforeInitialization方法。
上面的功能也可以通过@Autowired注解实现，都是注入。
