一、BeanPostProcessor与BeanFactoryPostProcessor的定义
一、BeanPostProcessor
bean后置处理器，bean创建对象初始化前后进行拦截工作的
二、BeanFactoryPostProcessor
beanFactory的后置处理器，在BeanFactory标准初始化之后调用，来定制和修改BeanFactory的内容，所有的bean定义信息已经保存加载到beanFactory，但是bean的实例还未创建。BeanFactoryPostProcessor是BeanFactory的一个钩子接口
二、原理
一、测试demo
@Component
public class MyBeanFactoryPostProcessor implements BeanFactoryPostProcessor {
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {
System.out.println("MyBeanFactoryPostProcessor...postProcessBeanFactory...");
int count = beanFactory.getBeanDefinitionCount();
String[] names = beanFactory.getBeanDefinitionNames();
System.out.println("当前BeanFactory中有"+count+" 个Bean");
System.out.println(Arrays.asList(names));
}
}
@ComponentScan("com.spring.annotate.beans")
@Configuration
public class BeansFactoryConfig {
@Bean
public Blue blue(){
return new Blue();
}
}
@Test
void contextLoads() {
AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext(BeansFactoryConfig.class);
applicationContext.close();
}结果：
二、原理
一、通过idea工具可以查看到spring源码接口，发现它还有一个子接口BeanDefinitionRegistryPostProcessor
二、BeanFactoryPostProcessor接口
@FunctionalInterface
public interface BeanFactoryPostProcessor {/**
* Modify the application context's internal bean factory after its standard
* initialization. All bean definitions will have been loaded, but no beans
* will have been instantiated yet. This allows for overriding or adding
* properties even to eager-initializing beans.
* @param beanFactory the bean factory used by the application context
* @throws org.springframework.beans.BeansException in case of errors
*/
void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;}
从源码上看，这个接口只有一个方法，也就是说spring是通过这个方法对BeanFactory进行增强的
三、BeanDefinitionRegistryPostProcessor接口
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;}
此接口也只有一个方法，是为了Bean的注册而生，BeanDefinitionRegistry 是BeanDefinition的注册器，而注册Bean的过程是将满足Bean条件的类解析为BeanDefinition对象然后注册到BeanDefinition注册器中。
总结：
BeanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor都是扩展Bean的加载方式，当我们需要自定义自己的Bean加载方式时实现BeanDefinitionRegistryPostProcessor接口即可。@Configuration注解的实现就是基于BeanDefinitionRegistryPostProcessor接口完成
四、BeanFactoryPostProcessor 原理
首先我们需要清楚，AbstractApplicationContext类中refresh()是spring加载Bean的核心方法，大部分的处理逻辑都是在这个方法中完成。执行时机是：所有的bean定义已经保存加载到beanFactory，但是bean的实例还未创建
@Override
public void refresh() throws BeansException, IllegalStateException {
synchronized (this.startupShutdownMonitor) {
StartupStep contextRefresh = this.applicationStartup.start("spring.context.refresh");
// Prepare this context for refreshing.
/**
* 准备上下文刷新工作，如设置初始值
*/
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
/**
* 告诉子类刷新内部beanFactory，返回Bean工厂
*/
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
/**
* 准备beanFactory，以便于上下文中使用
*/
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
/**
* 允许在上下文子类中对bean工厂进行后处理。
*/
postProcessBeanFactory(beanFactory);
/**
* 开启处理PostProcessors步骤器
*/
StartupStep beanPostProcess = this.applicationStartup.start("spring.context.beans.post-process");
// Invoke factory processors registered as beans in the context.
/**
* 调用BeanFactory的后置处理器
*/
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
/**
*
* 注册拦截bean创建的bean处理器
*/
registerBeanPostProcessors(beanFactory);
/**
* 处理PostProcessors步骤器
*/
beanPostProcess.end();
// Initialize message source for this context.
/**
* 初始化MessageSource
*/
initMessageSource();
// Initialize event multicaster for this context.
/**
* 初始化Application监听器的管理Bean（ApplicationEventMulticaster）
*/
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
/**
* 模板模式，刷新Bean的操作，由子类实现具体逻辑
*/
onRefresh();
// Check for listener beans and register them.
/**
* 检查和注册监听器
*/
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
/**
* 实例化所有（非惰性初始化）单例
*/
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
/**
* 发布相应的事件
*/
finishRefresh();
}
catch (BeansException ex) {
if (logger.isWarnEnabled()) {
logger.warn("Exception encountered during context initialization - " +
"cancelling refresh attempt: " + ex);
}
// Destroy already created singletons to avoid dangling resources.
destroyBeans();
// Reset 'active' flag.
cancelRefresh(ex);
// Propagate exception to caller.
throw ex;
}
finally {
// Reset common introspection caches in Spring's core, since we
// might not ever need metadata for singleton beans anymore...
resetCommonCaches();
contextRefresh.end();
}
}
}
一、 ioc容器创建对象
二、invokeBeanFactoryPostProcessors(beanFactory);
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
/**
* 执行BeanFactoryPostProcessor，是该方法的处理核心
*/
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)
/**
* 检查和赋初始值
*/
if (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
三、PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())方法
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
Set<String> processedBeans = new HashSet<>();
/**
* 首先调用BeanDefinitionRegistryPostProcessors（如果有）。
*/
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
/**
* 用于存放BeanFactoryPostProcessor的对象
*/
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
/**
* 用户存放BeanDefinitionRegistryPostProcessor对象
*/
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
/********************************* 下面处理BeanDefinitionRegistryPostProcessor逻辑 *************************************/
/**
* 遍历最原始的BeanFactoryPostProcessor列表，找出BeanDefinitionRegistryPostProcessor和 BeanFactoryPostProcessor
* BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子接口
*/
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
/**
* 执行BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry
*/
registryProcessor.postProcessBeanDefinitionRegistry(registry);
registryProcessors.add(registryProcessor);
}
else {
regularPostProcessors.add(postProcessor);
}
}
/**
* 定义当前找到的BeanDefinitionRegistryPostProcessor临时存储
*/
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 首先，调用实现PriorityOrdered的BeanDefinitionRegistryPostProcessor。
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// 接下来，调用实现Ordered的BeanDefinitionRegistryPostProcessor。
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// 最后，调用所有其他BeanDefinitionRegistryPostProcessor，直到不再出现其他BeanDefinitionRegistryPostProcessor。
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, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
}
/**
* 批量执行BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry
*/
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
/**
* 批量执行BeanFactoryPostProcessor（最开始的BeanFactoryPostProcessor）
*/
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
/********************************* 下面处理BeanFactoryPostProcessor逻辑（可能执行上面步骤产生新的BeanFactoryPostProcessor），执行逻辑和BeanDefinitionRegistryPostProcessor一致 *************************************/
// 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<>(orderedPostProcessorNames.size());
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<>(nonOrderedPostProcessorNames.size());
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();
}
/**
* 排序BeanFactoryPostProcessor
* @param postProcessors
* @param beanFactory
*/
private static void sortPostProcessors(List<?> postProcessors, ConfigurableListableBeanFactory beanFactory) {
// Nothing to sort?
if (postProcessors.size() <= 1) {
return;
}
Comparator<Object> comparatorToUse = null;
if (beanFactory instanceof DefaultListableBeanFactory) {
comparatorToUse = ((DefaultListableBeanFactory) beanFactory).getDependencyComparator();
}
if (comparatorToUse == null) {
comparatorToUse = OrderComparator.INSTANCE;
}
postProcessors.sort(comparatorToUse);
}
/**
* 执行 BeanDefinitionRegistryPostProcessor
* @param postProcessors
* @param registry
* @param applicationStartup
*/
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry, ApplicationStartup applicationStartup) {
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
StartupStep postProcessBeanDefRegistry = applicationStartup.start("spring.context.beandef-registry.post-process")
.tag("postProcessor", postProcessor::toString);
postProcessor.postProcessBeanDefinitionRegistry(registry);
postProcessBeanDefRegistry.end();
}
}
/**
* 执行invokeBeanFactoryPostProcessors
* @param postProcessors
* @param beanFactory
*/
private static void invokeBeanFactoryPostProcessors(
Collection<? extends BeanFactoryPostProcessor> postProcessors, ConfigurableListableBeanFactory beanFactory) {
for (BeanFactoryPostProcessor postProcessor : postProcessors) {
StartupStep postProcessBeanFactory = beanFactory.getApplicationStartup().start("spring.context.bean-factory.post-process")
.tag("postProcessor", postProcessor::toString);
postProcessor.postProcessBeanFactory(beanFactory);
postProcessBeanFactory.end();
}
}
一、遍历最原始的BeanFactoryPostProcessor，找到BeanDefinitionRegistryPostProcessor和BeanFactoryPostProcessor，且执行BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry(registry)方法加载Bean。
二、从BeanFactory中寻找BeanDefinitionRegistryPostProcessor的PriorityOrdered（最高优先级的排序）类型Bean，排序后执行postProcessBeanDefinitionRegistry(registry)方法加载Bean。
三、从BeanFactory中寻找BeanDefinitionRegistryPostProcessor未被加载的Ordered（排序）类型Bean，排序后执行postProcessBeanDefinitionRegistry(registry)方法加载Bean。
四、从BeanFactory中寻找出未被加载的BeanDefinitionRegistryPostProcessor类型Bean，然后执行postProcessBeanDefinitionRegistry(registry)方法加载Bean，这一步目的就是处理加载新的BeanDefinitionRegistryPostProcessor的Bean。
五、从BeanFactory中寻找BeanFactoryPostProcessor的PriorityOrdered（最高优先级的排序）类型Bean，排序后执行postProcessBeanFactory(beanFactory)方法加载Bean。
六、从BeanFactory中寻找BeanFactoryPostProcessor未被加载的Ordered（排序）的类型Bean，排序后执行postProcessBeanFactory(beanFactory)方法加载Bean。
七、从BeanFactory中寻找出未排序的BeanFactoryPostProcessor类型Bean，然后执行postProcessBeanFactory(beanFactory)方法加载Bean。
- priorityOrderedPostProcessors：放置有优先级排序的接口
- orderedPostProcessorNames：放置有排序的PostProcessorNames
- nonOrderedPostProcessorNames：放置普通的PostProcessorNames
五、BeanDefinitionRegistryPostProcessor原理
执行时机：在所有bean定义信息将要被加载，bean实例还未创建的，这个是将要被加载，BeanFactoryPostProcessor 这个是已经被加载，所以BeanDefinitionRegistryPostProcessor是在更前执行
1、BeanDefinition：容器中的每一个bean都会有一个对应的
BeanDefinition实例，该实例负责保存bean对象的所有必要信息，包括bean对象的class类型、是否是抽象类、构造方法和参数、其它属性等等。2、BeanDefinitionRegistry：
BeanDefinition是定义bean的，BeanDefinitionRegistry则是bean定义信息的保存中心，也叫注册中心，保存了bean的所有定义，以后BeanFactory就是按照BeanDefinitionRegistry里面保存的每一个bean定义信息创建bean实例。bean是单例还是多例，bean的类型，bean的ID等信息，都是存在BeanDefinitionRegistry里面。
3、BeanDefinitionRegistryPostProcessor：它是Spring框架的一个扩展点，用于对Bean定义的注册过程进行干预和定制。继承BeanFactoryPostProcessor接口，并在其基础上扩展了一个新的方法，即：postProcessBeanDefinitionRegistry()方法。
用途：在Spring容器初始化时，首先会读取应用程序中的配置文件，并解析出所有的Bean定义，然后将这些Bean定义注册到容器中。在这个过程中，BeanDefinitionRegistryProcessor提供了一种机制，允许开发人员在Bean定义注册之前和之后对Bean定义进行自定义处理，例如添加，修改或删除Bean定义等。
方法详解：postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry)：该方法在所有Bean定义加载完成之后，Bean实例化之前被调用，允许开发人员对Bean定义进行自定义修改，例如添加，修改或删除Bean定义等。
postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory): 该方法是继承自BeanFactoryPostProcessor接口的方法，用于在BeanFactory完成实例化之后对BeanFactory进行后置处理。
一、ioc容器创建
二、调用refresh()方法，执行到里面的invokeBeanFactoryPostProcessors(beanFactory);方法
进入PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());
三、从容器中获取到所有的BeanDefinitionRegistryPostProcessor组件
private static void invokeBeanDefinitionRegistryPostProcessors(
Collection<? extends BeanDefinitionRegistryPostProcessor> postProcessors, BeanDefinitionRegistry registry) {
for (BeanDefinitionRegistryPostProcessor postProcessor : postProcessors) {
postProcessor.postProcessBeanDefinitionRegistry(registry);
}
}1、依次触发所有的postProcessBeanDefinitionRegistry()方法
2、再来触发postProcessBeanFactory()方法，是BeanFactoryPostProcessor里面的方法。
四、最后到BeanFactoryPostProcessor组件时还会依次触发postProcessBeanFactory()方法
