BeanFactoryPostProcessor会在invokeBeanFactoryPostProcessors(beanFactory)方法中被调用。
invokeBeanFactoryPostProcessors(beanFactory)方法在AbstractApplicationContext.refresh()方法中被调用。
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
// 调用BeanFactoryPostProcessor
//将我们自己的bean转换为beanDefinition
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
initMessageSource();
// Initialize event multicaster for this context.
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
onRefresh();
// Check for listener beans and register them.
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//推断构造方法
//通过反射new对象
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
finishRefresh();
}
/**
* ...代码段
*/
}
本方法会执行所有的实现了BeanFactoryPostProcessor及其子接口BeanDefinitionRegistryPostProcess的类的postProcessBeanDefinitionRegistry方法和postProcessBeanFactory方法
BeanFactoryPostProcessor：Bean工厂的后置处理器，类图：
Spring IoC 容器允许 BeanFactoryPostProcessor 在容器实例化任何 bean 之前读取 bean 的定义，并可以修改它。
分析
invokeBeanFactoryPostProcessors
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
//通过getBeanFactoryPostProcessors()方法得到所有已注册的BeanFactoryPostPorcessor
//通常情况下这里"已注册的BeanFactoryPostPorcessor"仅包含用户自定义的且手动添加（非注解添加）到上下文的BeanFactoryPostPorcessor
//调用所有的BeanFactoryPostPorcessor（包括所有已注册和未注册的）
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
// Detect a LoadTimeWeaver and prepare for weaving, if found in the meantime
// (e.g. through an @Bean method registered by ConfigurationClassPostProcessor)
if (beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
getBeanFactoryPostProcessors
//用户没有手动添加BeanFactoryPostProcessor到上下文时，返回空list
public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
return this.beanFactoryPostProcessors;
}
在invokeBeanFactoryPostProcessors方法中，首先通过getBeanFactoryPostProcessors方法等得到所有已注册的BeanFactoryPostProcessor的list，然后将此list作为参数传入PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors。
通常情况下这里"已注册的BeanFactoryPostPorcessor"仅包含用户自定义的且手动添加（非注解添加）到上下文的BeanFactoryPostPorcessor。
如果用户没有手动添加BeanFactoryPostProcessor到上下文时，getBeanFactoryPostProcessors发放返回空list。
用户自定义的且手动添加（非注解添加）到上下文的BeanFactoryPostPorcessor？
用户自动义且通过注解添加到上下文的BeanFactoryPostPorcessor
@Component
public class MyAnnoBeanFactoryPostPorcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyAnnoBeanFactoryPostProcessor-----");
}
}
@Component
public class MyAnnoBeanDefinitionRegistryPostProcess implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("MyAnnoBeanDefinitionRegistryPostProcess---postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyAnnoBeanDefinitionRegistryPostProcess---postProcessBeanFactory");
}
}
用户自动义且手动添加到上下文的BeanFactoryPostPorcessor
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyBeanFactoryPostPorcessor----");
}
}
public class MyBeanDefinitionRegistryPostProcess implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("MyBeanDefinitionRegistryPostProcess---postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyBeanDefinitionRegistryPostProcess---postProcessBeanFactory");
}
}
public static void main(String[] args) {
// AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext(AppConfig.class);
MyBeanFactoryPostProcessor myBeanFactoryPostProcessor = new MyBeanFactoryPostProcessor();
MyBeanDefinitionRegistryPostProcess myBeanDefinitionRegistryPostProcess = new MyBeanDefinitionRegistryPostProcess();
AnnotationConfigApplicationContext ac = new AnnotationConfigApplicationContext();
ac.addBeanFactoryPostProcessor(myBeanFactoryPostProcessor);
ac.addBeanFactoryPostProcessor(myBeanDefinitionRegistryPostProcess);
ac.register(AppConfig.class);
ac.refresh();
System.out.println(ac.getBean("indexService"));
}
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors
/**
* 调用所有的BeanFactoryPostProcessor及其子接口BeanDefinitionRegistryPostProcess的实现类
* 的postProcessBeanDefinitionRegistry方法和postProcessBeanFactory方法
*
* 调用顺序为：
* 1，手动添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
* 2，实现PriorityOrdered接口且是通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
* 其中ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法
* 完成用户bean的beanDefinition扫描并放入beanDefinitionMap和beanDefinitionNames中
* 3，实现Order接口且是通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
* 4，通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
* 注意：执行postProcessBeanDefinitionRegistry可能会添加新的BeanDefinitionRegistryPostProcess，
* 所以最后通过while循环执行，直到没有新的为止
* 5，手动添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanFactory方法
* 6，通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanFactory方法
* 包括ConfigurationClassPostProcessor的postProcessBeanFactory方法
* 7，手动添加到上下文的BeanFactoryPostPorcessor的实现类的postProcessBeanFactory方法
* 8，实现PriorityOrdered接口且是通过注解添加到上下文的BeanFactoryPostPorcessor接口的实现类的postProcessBeanFactory方法
* 9，实现Ordered接口且是通过注解添加到上下文的BeanFactoryPostPorcessor接口的实现类的postProcessBeanFactory方法
* 10，通过注解添加到上下文的BeanFactoryPostPorcessor接口的实现类postProcessBeanFactory方法
*/
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
//beanFactory = new DefaultListableBeanFactory()
//DefaultListableBeanFactory实现了BeanDefinitionRegistry，因此判断为true
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
//注意这两个list的泛型
//这两个list的作用是：在调用所有的postProcessBeanDefinitionRegistry方法后，用于调用postProcessBeanFactory方法
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
//首先处理入参中的beanFactoryPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
//如果是BeanDefinitionRegistryPostProcessor，
//直接调用postProcessBeanDefinitionRegistry方法
//并放入相应的list
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
//否则就是BeanFactoryPostProcessor，放入对应的list
regularPostProcessors.add(postProcessor);
}
}
// 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.
//临时变量
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
//首先，调用所有实现PriorityOrdered接口且已添加到上下文的BeanDefinitionRegistryPostProcessors的实现类的postProcessBeanDefinitionRegistry方法
/**
* 在用户没有自定义BeanDefinitionRegistryPostProcessor的情况下，此处只有一个ConfigurationClassPostProcessor
*/
//1，找出所有BeanDefinitionRegistryPostProcessor的实现类
// 这个方法会多次调用，因为BeanDefinitionRegistryPostProcessor执行后可能会添加新的BeanDefinitionRegistryPostProcessors
//2，过滤实现PriorityOrdered接口
//3，过滤已经调用过的
//4，排序
//5，加入list
//6，依次调用postProcessBeanDefinitionRegistry
//7，清空临时变量
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);
//执行ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法，扫描用户bean，放入beanDefinitionMap和beanDefinitionNames
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
//接下来，调用所有实现Ordered接口且已添加到上下文的BeanDefinitionRegistryPostProcessor的实现类的postProcessBeanDefinitionRegistry方法
//除第二步过滤Order接口外，步骤与上面一致
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.
//最后，调用所有剩下的已添加到上下文的BeanDefinitionRegistryPostProcessor的实现类的postProcessBeanDefinitionRegistry方法
//上面已经说过，调用postProcessBeanDefinitionRegistry方法时，可能会添加新的BeanDefinitionRegistryPostProcessor，
// 所以此处使用循环，直到没有新的BeanDefinitionRegistryPostProcessor为止
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.
//调用所有BeanDefinitionRegistryPostProcessor实现类的postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
//调用用户自定义的BeanFactoryPostProcessor接口的实现类且是手动添加到上下文（没有使用注解自动扫描）的postProcessBeanFactory方法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
//开始调用用户使用注解添加的BeanFactoryPostProcessor接口的实现类的postProcessBeanFactory方法
//执行顺序：1，实现PriorityOrdered接口；2，实现Ordered接口；3，其他
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
List<String> orderedPostProcessorNames = new ArrayList<>();
List<String> nonOrderedPostProcessorNames = new ArrayList<>();
for (String ppName : postProcessorNames) {
if (processedBeans.contains(ppName)) {
// skip - already processed in first phase above
}
else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
}
else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
orderedPostProcessorNames.add(ppName);
}
else {
nonOrderedPostProcessorNames.add(ppName);
}
}
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>();
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
// Finally, invoke all other BeanFactoryPostProcessors.
List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();
}
执行过程可以看上面代码段的注释。
“执行postProcessBeanDefinitionRegistry可能会添加新的BeanDefinitionRegistryPostProcess”，这句话改怎么理解？
举例说明：
public class MyRegisterBeanDefinitionRegistryPostPorcessor implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
System.out.println("MyRegisterBeanDefinitionRegistryPostPorcessor---postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyRegisterBeanDefinitionRegistryPostPorcessor---postProcessBeanFactory");
}
}
@Component
public class MyAnnoBeanDefinitionRegistryPostProcess implements BeanDefinitionRegistryPostProcessor {
@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
BeanDefinition bd = registry.getBeanDefinition("myAnnoBeanDefinitionRegistryPostProcess");
bd.setBeanClassName(MyRegisterBeanDefinitionRegistryPostPorcessor.class.getName());
//将BeanDefinition的属性改变后，当做新的BeanDefinition注册到容器中
registry.registerBeanDefinition("myRegisterBeanDefinitionRegistryPostPorcessor", bd);
System.out.println("MyAnnoBeanDefinitionRegistryPostProcess---postProcessBeanDefinitionRegistry");
}
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyAnnoBeanDefinitionRegistryPostProcess---postProcessBeanFactory");
}
}
MyRegisterBeanDefinitionRegistryPostPorcessor既没有通过注解，也没有手动添加到上下文中。
在调用MyAnnoBeanDefinitionRegistryPostProcess的postProcessBeanDefinitionRegistry方法时，将MyRegisterBeanDefinitionRegistryPostPorcessor包装成BeanDefinition注册到容器中，MyRegisterBeanDefinitionRegistryPostPorcessor中的方法也会在invokeBeanFactoryPostProcessors方法的循环调用阶段被调用。
总结
BeanFactoryPostProcessor作用于BeanDefinition阶段（bean实例化之前），可以修改bean的定义。
BeanDefinitionRegistryPostPorcessor比BeanFactoryPostProcessors有更高的优先级，在BeanFactoryPostProcessors之前执行。
BeanDefinitionRegistryPostPorcessor执行过程中会出现“套娃现象”：注册新的BeanFactoryPostProcessors。
调用顺序：
1，手动添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
2，实现PriorityOrdered接口且是通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
* 其中ConfigurationClassPostProcessor的postProcessBeanDefinitionRegistry方法
* 完成用户bean的beanDefinition扫描并放入beanDefinitionMap和beanDefinitionNames中
3，实现Order接口且是通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
4，通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanDefinitionRegistry方法
* 注意：执行postProcessBeanDefinitionRegistry可能会添加新的BeanDefinitionRegistryPostProcess，
* 所以最后通过while循环执行，直到没有新的为止
5，手动添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanFactory方法
6，通过注解添加到上下文的BeanDefinitionRegistryPostProcess接口的实现类的postProcessBeanFactory方法
* 包括ConfigurationClassPostProcessor的postProcessBeanFactory方法
7，手动添加到上下文的BeanFactoryPostPorcessor的实现类的postProcessBeanFactory方法
8，实现PriorityOrdered接口且是通过注解添加到上下文的BeanFactoryPostPorcessor接口的实现类的postProcessBeanFactory方法
9，实现Ordered接口且是通过注解添加到上下文的BeanFactoryPostPorcessor接口的实现类的postProcessBeanFactory方法
10，通过注解添加到上下文的BeanFactoryPostPorcessor接口的实现类postProcessBeanFactory方法