概述
BeanFactoryPostProcessor是Spring提供的扩展接口之一，可用于对容器中的BeanDefinitions进行修改，例如：
- 向容器中添加新的
BeanDefinition; - 修改指定的
BeanDefiniton;
定义
Spring内置了两个后置处理器接口，定义如下：
- BeanFactoryPostProcessor
@FunctionalInterface
public interface BeanFactoryPostProcessor {
/**
* 在初始化前修改应用上下文 application context's 中所有的 bean 定义。
*/
void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;
}
- BeanDefinitionRegistryPostProcessor
public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
/**
* 在初始化前修改应用上下文 application context's 中 bean 的注册表。
*/
void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;
}
继承关系如下图所示：
BeanFactoryPostProcessor
调用入口
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 调用BeanFactoryPostProcessor
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()));
}
}
从上述方法调用可知，Spring通过PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())来调用BeanFactoryPostProcessors，接下来我们就详细来跟进解读下……
流程详解
- 方法声明
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List beanFactoryPostProcessors) {
- 定义
processedBeans用于缓存BeanFactoryPostProcessor的名称
Set processedBeans = new HashSet<>();
- 判断
beanFactory是否是BeanDefinitionRegistry的实例，如果不是，则直接调用，否则分开调用
if (beanFactory instanceof BeanDefinitionRegistry) {
...
}else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
- 第
3步中，简述了当beanFactory不是BeanDefinitionRegistry的情况，现在来看下当beanFactory是BeanDefinitionRegistry的情况下又是如何执行的呢。
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List regularPostProcessors = new ArrayList<>();
List registryProcessors = new ArrayList<>();
// 遍历beanFactoryPostProcessors
// a. 如果是BeanDefinitionRegistryPostProcessor，则调用其postProcessBeanDefinitionRegistry方法，并添加到registryProcessors
// b. 否则，缓存到regularPostProcessors
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 调用postProcessBeanDefinitionRegistry
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 添加到registryProcessors
registryProcessors.add(registryProcessor);
}
else {
// 缓存到regularPostProcessors
regularPostProcessors.add(postProcessor);
}
}
- 定义一个缓存池
currentRegistryProcessors，用于缓存分别实现了PriorityOrdered、Ordered接口以及未实现接口的BeanDefinitionRegistryPostProcessor。
List currentRegistryProcessors = new ArrayList<>();
- 调用实现了
PriorityOrdered接口的BeanDefinitionRegistryPostProcessor。
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 调用实现了 PriorityOrdered 接口的 BeanDefinitionRegistryPostProcessors
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();
- 调用实现了
Ordered接口的BeanDefinitionRegistryPostProcessor
// 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();
- 调用其它
BeanDefinitionRegistryPostProcessor。
// 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();
}
- 调用
BeanDefinitionRegistryPostProcessor的postProcessBeanFactory(beanFactory)方法
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
- 至此，当
beanFactory是BeanDefinitionRegistry的专有处理流程结束，接下来，我们再继续跟进通用的处理流程。
// 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);
- 将
BeanFactoryPostProcessor按实现了、和其它进行分类。
// Separate between BeanFactoryPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
List priorityOrderedPostProcessors = new ArrayList<>();
List orderedPostProcessorNames = new ArrayList<>();
List 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);
}
}
- 调用实现了
PriorityOrdered接口的BeanFactoryPostProcessor。
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
- 调用实现了
Ordered接口的BeanFactoryPostProcessor。
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
List orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String postProcessorName : orderedPostProcessorNames) {
orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
sortPostProcessors(orderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
- 调用其它
BeanFactoryPostProcessor。
// Finally, invoke all other BeanFactoryPostProcessors.
List nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String postProcessorName : nonOrderedPostProcessorNames) {
nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
}
invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
- 清理元数据缓存，至此，
Spring的Bean后置处理器BeanFactoryPostProcessor调用结束。
// Clear cached merged bean definitions since the post-processors might have
// modified the original metadata, e.g. replacing placeholders in values...
beanFactory.clearMetadataCache();