版权声明：如有转载，请标明出处，谢谢合作！ https://blog.csdn.net/lyc_liyanchao/article/details/82845257
接上文的分析，上文中已经分析了BeanFactoryPostProcessor的调用过程，接下来分析BeanPostProcessor的注册过程，注意这里只是注册，并没有实际调用，这里又涉及到spring bean的生命周期的一些问题，我们在前面的文章中已经分析过了，不在赘述，打开registerBeanPostProcessors方法。
8.注册BeanPostProcessors
public static void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during beanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
// 注册一个BeanPostProcessorChecker,它是BeanPostProcessor的子类
// 用于在BeanPostProcessor实例化期间创建bean时记录信息消息，即当bean不符合由所有BeanPostProcessors处理的资格时。
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered, Ordered, and the rest.
// 对实现了PriorityOrdered接口,Ordered接口,内部BeanPostProcessor和其他的BeanPostProcessor分类处理
List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
priorityOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
// 首先注册实现了PriorityOrdered(有限排序接口)BeanPostProcessor
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 其次,注册实现了Ordered(排序接口的)BeanPostProcessor
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
// 然后,注册无序的BeanPostProcessors
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
// 最后,注册内部BeanPostProcessors
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
// 注册一个ApplicationListenerDetector用来侦测ApplicationListener类型的bean
// 并将它们加入到容器的applicationEventMulticaster或applicationListeners集合中
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
BeanPostProcessor的注册过程和BeanFactoryPostProcessor的调用过程差不多，都是对处理器分类别进行处理，在这里Spring多注册了个特殊的BeanPostProcessor，BeanPostProcessorChecker和ApplicationListenerDetector，这两个处理器都是BeanPostProcessor有的实现，自然可以在bean的实例化之前和实例化之后对bean做一些处理，那么这些处理是什么呢？
- BeanPostProcessorChecker:摘取BeanPostProcessor中方法实现
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) {
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
if (!(bean instanceof BeanPostProcessor) && !isInfrastructureBean(beanName) &&
this.beanFactory.getBeanPostProcessorCount() < this.beanPostProcessorTargetCount) {
if (logger.isInfoEnabled()) {
logger.info("Bean '" + beanName + "' of type [" + bean.getClass().getName() +
"] is not eligible for getting processed by all BeanPostProcessors " +
"(for example: not eligible for auto-proxying)");
}
}
return bean;
}
从postProcessAfterInitialization方法可以看到，该处理器并没有对bean做特殊处理，只是当bean不符合BeanPostProcessors的处理资格时，打印日志做下记录！
- ApplicationListenerDetector:摘取BeanPostProcessor中方法实现
@Override
public Object postProcessBeforeInitialization(Object bean, String beanName) {
return bean;
}
@Override
public Object postProcessAfterInitialization(Object bean, String beanName) {
if (bean instanceof ApplicationListener) {
// potentially not detected as a listener by getBeanNamesForType retrieval
Boolean flag = this.singletonNames.get(beanName);
if (Boolean.TRUE.equals(flag)) {
// singleton bean (top-level or inner): register on the fly
this.applicationContext.addApplicationListener((ApplicationListener<?>) bean);
}
else if (Boolean.FALSE.equals(flag)) {
if (logger.isWarnEnabled() && !this.applicationContext.containsBean(beanName)) {
// inner bean with other scope - can't reliably process events
logger.warn("Inner bean '" + beanName + "' implements ApplicationListener interface " +
"but is not reachable for event multicasting by its containing ApplicationContext " +
"because it does not have singleton scope. Only top-level listener beans are allowed " +
"to be of non-singleton scope.");
}
this.singletonNames.remove(beanName);
}
}
return bean;
}
从代码中可以发现，当bean是ApplicationListener且是单例模式的bean时，则将监听器加入到applicationContext容器中，否则打印日志并将bean从当前类缓存集合中移除（不是从容器中移除）
今天的分析就先到这里了，注册过还是比较简单的