spring中实现BeanPostProcessor的后置处理器
ApplicationContextAwareProcessor
进入该实现类内部
可以看到：该类帮我们组建IOC容器，判断我们的bean有没有实现ApplicationContextAware接口，并作出相应处理(setApplicationContext方法)
测试：调试一个实现ApplicationContextAware接口的类的创建过程
public class User implements ApplicationContextAware {
private ApplicationContext applicationContext;
public User(){
System.out.println("User...constructor....");
}
@PostConstruct
public void init(){
System.out.println("User...init....");
}
@PreDestroy
public void destroy(){
System.out.println("User...destroy....");
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
/**
* 容器初始化，将applicationContext作为参数传入，其它方法就可以使用容器了
* 该方法是由ApplicationContextAwareProcessor处理器来执行的
*/
this.applicationContext = applicationContext;
}
}
在ApplicationContextAwareProcessor类的postProcessBeforeInitialization方法中添加断点
public Object postProcessBeforeInitialization(final 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)) {//1
acc = this.applicationContext.getBeanFactory().getAccessControlContext();
}
if (acc != null) {
AccessController.doPrivileged(new PrivilegedAction<Object>() {
public Object run() {
ApplicationContextAwareProcessor.this.invokeAwareInterfaces(bean);
return null;
}
}, acc);
} else {
this.invokeAwareInterfaces(bean);//2
}
return bean;
}
注释1：创建User对象，初始化之前，先判断User类是否实现了ApplicationContextAware接口
注释2：调用invokeAwareInterfaces方法给bean设置值
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);
}
}
}
invokeAwareInterfaces方法中判断该bean属于哪个Aware实例，并进行相应设值处理。如果Aware是ApplicationContextAware，就将当前bean转成ApplicationContextAware类型并调用setApplicationContext方法将ApplicationContext值设置到bean中
调试：
在bean是User类型时，setApplicationContext方法会得到执行，也即user对象中设置了ioc容器，可以在user的其它方法中使用该容器
BeanValidationPostProcessor
public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
if (!this.afterInitialization) {
this.doValidate(bean);
}
return bean;
}
public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
if (this.afterInitialization) {
this.doValidate(bean);
}
return bean;
}
postProcessBeforeInitialization方法用于初始化前校验
postProcessAfterInitialization方法用于初始化后校验
InitDestroyAnnotationBeanPostProcessor
该处理器用于处理@PostConstruct、@PreDestroy注解
利用反射调用bean生命周期的相关方法