spring中的BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子接口，BeanFactoryPostProcessor的作用是在bean
的定义信息已经加载但还没有初始化的时候执行方法postProcessBeanFactory(）方法，而BeanDefinitionRegistryPostProcessor是在
BeanFactoryPostProcessor的前面执行。
public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
/**
* Modify the application context's internal bean definition registry after its
* standard initialization. All regular bean definitions will have been loaded,
* but no beans will have been instantiated yet. This allows for adding further
* bean definitions before the next post-processing phase kicks in.
* @param registry the bean definition registry used by the application context
* @throws org.springframework.beans.BeansException in case of errors
*/
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
}自定义一个实现了BeanDefinitionRegistryPostProcessor接口的MyBeanDefinitionRegistryPostProcessor 实现类，它会重写
BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry（）方法和BeanFactoryPostProcessor的postProcessBeanFactory（）方法
@Component
public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
//BeanDefinitionRegistry可以给容器注册bean
System.out.println("MyBeanDefinitionRegistryPostProcessor...添加了foo之前的bean数="+registry.getBeanDefinitionCount());
RootBeanDefinition rootBeanDefinition = new RootBeanDefinition(Foo.class);
registry.registerBeanDefinition("helloFoo",rootBeanDefinition);
} @Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
int beanDefinitionCount = beanFactory.getBeanDefinitionCount();
System.out.println("MyBeanDefinitionRegistryPostProcessor...postProcessBeanFactory...的bean数="+beanDefinitionCount);
}
}
配置类:
@Configuration
@Import({MyBeanDefinitionRegistryPostProcessor.class})
public class ExtConfig { @Bean
public Foo foo(){
return new Foo();
}
}
foo类：
public class Foo {
public Foo(){
System.out.println("bean的创建");
}
@PostConstruct
public void init(){
System.out.println("bean的初始化");
}
@PreDestroy
public void destroy(){
System.out.println("bean的销毁");
}
}测试结果：
MyBeanDefinitionRegistryPostProcessor...添加了foo之前的bean数9
MyBeanDefinitionRegistryPostProcessor...postProcessBeanFactory...的bean数+10
bean的创建
bean的初始化
bean的创建
bean的初始化
debug:refresh()--》invokeBeanFactoryPostProcessors(),这里和注册bean和beanFactory类似，按照优先级的的来进行。
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// Separate between BeanDefinitionRegistryPostProcessors that implement
// PriorityOrdered, Ordered, and the rest.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<BeanDefinitionRegistryPostProcessor>(); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear(); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear(); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
boolean reiterate = true;
while (reiterate) {
reiterate = false;
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
if (!processedBeans.contains(ppName)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
reiterate = true;
}
}
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
} // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
invokeBeanDefinitionRegistryPostProcessors（）方法：
/**
* Invoke the given BeanDefinitionRegistryPostProcessor beans.
*/
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) { for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}
最后去执行invokeBeanFactoryPostProcessors（）方法；
/**
* Invoke the given BeanFactoryPostProcessor beans.
*/
private static void invokeBeanFactoryPostProcessors(
Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) { for (BeanFactoryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanFactory(beanFactory);
}
}
它获取到所有的BeanFactoryPostProcessor 后，遍历执行每一个具体的方法：在这里会去调用
MyBeanDefinitionRegistryPostProcessor的postProcessBeanFactory（）方法：