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【spring】深入了解spring的PostProcessors
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PostProcessors简单介绍
- 本文源码基于spring-framework-5.3.10。
- 主要包括：BeanPostProcessor、BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor
- 本文侧重点在启动的过程中，实例化非懒加载的单例Bean之前
BeanPostProcessor常用的有什么
- 主要存在：private final List
beanPostProcessors中。 - AutowiredAnnotationBeanPostProcessor：处理@Autowired、@Value
- CommonAnnotationBeanPostProcessor：处理@Resource、@PostConstruct、@PreDestroy
- ApplicationContextAwareProcessor：处理ApplicationContextAware等回调
BeanFactoryPostProcessor执行顺序：先执行注册，后执行处理
- 执行通过ApplicationContext添加进来的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
- 执行BeanFactory中实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
- 执行BeanFactory中实现了Ordered接口的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
- 执行BeanFactory中其他的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
- 执行上面所有的BeanDefinitionRegistryPostProcessor的postProcessBeanFactory()方法
执行通过ApplicationContext添加进来的BeanFactoryPostProcessor的postProcessBeanFactory()方法 - 执行BeanFactory中实现了PriorityOrdered接口的BeanFactoryPostProcessor的postProcessBeanFactory()方法
- 执行BeanFactory中实现了Ordered接口的BeanFactoryPostProcessor的postProcessBeanFactory()方法
- 执行BeanFactory中其他的BeanFactoryPostProcessor的postProcessBeanFactory()方法
Lifecycle的使用
registerBeanPostProcessors源码分析
/**
* 源码位于：org.springframework.context.support.AbstractApplicationContext.registerBeanPostProcessors(ConfigurableListableBeanFactory)
* 将扫描到的BeanPostProcessors实例化并排序，并添加到BeanFactory的beanPostProcessors属性中去。
* 在掉用这个方法之前会在加载reader的时候配置（这里生成BeanDefinition放入Bean工厂的BeanDefinitinoMap属性）：new RootBeanDefinition(AutowiredAnnotationBeanPostProcessor.class);
* 在掉用这个方法之前会在加载reader的时候配置（这里生成BeanDefinition放入Bean工厂的BeanDefinitinoMap属性）：new RootBeanDefinition(CommonAnnotationBeanPostProcessor.class);
* 在掉用这个方法之前会在prepareBeanFactory的时候配置（这里会加入到List<BeanPostProcessor> beanPostProcessors这个变量中）：beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
* 在掉用这个方法之前会在prepareBeanFactory的时候配置（这里会加入到List<BeanPostProcessor> beanPostProcessors这个变量中）：beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
*/
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
/**
* 具体的注册BeanPostProcessor方法
*/
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
// 拿到所有的BeanPostProcessor的子类
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.
// beanProcessorTargetCount表示BeanFactory中所有的BeanPostProcessor数量，+1表示BeanPostProcessorChecker
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
// 将不同类型的BeanPostProcessor进行分类
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.
// 升序排序，执行BeanFactory中实现了PriorityOrdered接口的BeanPostProcessor的addBeanPostProcessor()方法，添加到beanPostProcessors变量中
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
// 实现了Ordered注解的逻辑处理
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
for (String ppName : orderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
orderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
// 升序排序，执行BeanFactory中实现了Ordered接口的BeanPostProcessor的addBeanPostProcessor()方法，添加到beanPostProcessors变量中
sortPostProcessors(orderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, orderedPostProcessors);
// Now, register all regular BeanPostProcessors.
// 其他的BeanPostProcessor处理
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
// 执行BeanFactory中实现了Ordered接口的BeanPostProcessor的addBeanPostProcessor()方法，添加到beanPostProcessors变量中
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
// MergedBeanDefinitionPostProcessor排在最后,这里可以理解为spring内部的BeanPostProcessor排在最后
// 执行BeanFactory中实现了MergedBeanDefinitionPostProcessor接口的BeanPostProcessor的addBeanPostProcessor()方法，添加到beanPostProcessors变量中
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).
// ApplicationListenerDetector放在所有BeanPostProcessor之后，注意ApplicationListenerDetector的equals()方法实现
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
invokeBeanFactoryPostProcessors源码分析
/**
* 源码位于：org.springframework.context.support.AbstractApplicationContext.invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory)
* 在掉用这个方法之前会在加载reader的时候配置（这里生成BeanDefinition放入Bean工厂的BeanDefinitinoMap属性）：new RootBeanDefinition(ConfigurationClassPostProcessor.class);
* 在掉用这个方法之前会在加载reader的时候配置：beanFactory.setDependencyComparator(AnnotationAwareOrderComparator.INSTANCE);
*/
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
// 有顺序的执行BeanFactoryPostProcessors的方法
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)
// LoadTimeWeaver相关。
if (!NativeDetector.inNativeImage() && beanFactory.getTempClassLoader() == null && beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
}
/**
* BeanFactoryPostProcessors按入场方式分为：
* 1. 程序员调用ApplicationContext的API手动添加
* 2. Spring自己扫描出来的
*
* BeanFactoryPostProcessor按类型又可以分为：
* 1. 普通BeanFactoryPostProcessor
* 2. BeanDefinitionRegistryPostProcessor
*
* 执行顺序顺序如下：
* 1. 执行手动添加的BeanDefinitionRegistryPostProcessor 的postProcessBeanDefinitionRegistry()方法
* 2. 执行扫描出来的BeanDefinitionRegistryPostProcessor（实现了PriorityOrdered）的postProcessBeanDefinitionRegistry()方法
* 3. 执行扫描出来的BeanDefinitionRegistryPostProcessor（实现了Ordered） 的postProcessBeanDefinitionRegistry()方法
* 4. 执行扫描出来的BeanDefinitionRegistryPostProcessor（普通） 的postProcessBeanDefinitionRegistry()方法
* 5. 执行扫描出来的BeanDefinitionRegistryPostProcessor（所有） 的postProcessBeanFactory()方法
* 6. 执行手动添加的BeanFactoryPostProcessor 的postProcessBeanFactory()方法
* 7. 执行扫描出来的BeanFactoryPostProcessor（实现了PriorityOrdered） 的postProcessBeanFactory()方法
* 8. 执行扫描出来的BeanFactoryPostProcessor（实现了Ordered） 的postProcessBeanFactory()方法
* 9. 执行扫描出来的BeanFactoryPostProcessor（普通） 的postProcessBeanFactory()方法
*
* ConfigurationClassPostProcessor就会在第2步执行，会进行扫描
*
* beanFactory:是他的Bean工厂
* beanFactoryPostProcessors:可能有BeanFactoryPostProcessor、BeanDefinitionRegistryPostProcessor
*/
public static void invokeBeanFactoryPostProcessors(
ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
// Invoke BeanDefinitionRegistryPostProcessors first, if any.
Set<String> processedBeans = new HashSet<>();
if (beanFactory instanceof BeanDefinitionRegistry) {
BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();
// beanFactoryPostProcessors集合一般情况下都是空的，除非我们手动调用容器的addBeanFactoryPostProcessor方法添加了
// beanFactoryPostProcessors中可能包含了：普通BeanFactoryPostProcessor对象和BeanDefinitionRegistryPostProcessor对象
// 对于BeanDefinitionRegistryPostProcessor对象，会执行自己的postProcessBeanDefinitionRegistry()方法
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
// 存在beanFactoryPostProcessors，会进行分类确定是子接口还是当前的
if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
BeanDefinitionRegistryPostProcessor registryProcessor =
(BeanDefinitionRegistryPostProcessor) postProcessor;
// 是子类的话，先调用注册的方法。
// 执行通过ApplicationContext添加进来的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
registryProcessor.postProcessBeanDefinitionRegistry(registry);
// 添加到registryProcessors
registryProcessors.add(registryProcessor);
}
else {
// 当前类是父类，不进行任何代码的执行，直接添加到regularPostProcessors
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.
List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();
// 执行扫描出来的BeanDefinitionRegistryPostProcessor
// First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.
// 首次进来只会拿到ConfigurableListableBeanFactory
String[] postProcessorNames =
beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// 它实现了PriorityOrdered接口的时候，才会真正的创建Bean
if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
// 升序排序，使用PriorityOrdered的getOrder进行比较
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 执行刚刚找到的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法。
// 执行BeanFactory中实现了PriorityOrdered接口的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
// ConfigurableListableBeanFactory的postProcessBeanDefinitionRegistry内部会进行扫描！
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
// 继续来获取实现了BeanDefinitionRegistryPostProcessor的类，进过来扫描，这里可以发现程序员自定义的Bean
postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
for (String ppName : postProcessorNames) {
// processedBeans表示该beanFactoryPostProcessor的postProcessBeanDefinitionRegistry()方法已经执行过了，不再重复执行
// 简单理解就是过滤掉之前已经执行过的，准备去执行实现Ordered接口的。
if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
processedBeans.add(ppName);
}
}
// 排序
sortPostProcessors(currentRegistryProcessors, beanFactory);
registryProcessors.addAll(currentRegistryProcessors);
// 执行程序员自定义（包括上面为执行的）的实现了BeanDefinitionRegistryPostProcessor接口并且实现了Ordered接口的postProcessBeanDefinitionRegistry方法
// 执行BeanFactory中实现了Ordered接口的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup());
currentRegistryProcessors.clear();
// Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
// 执行哪些没有实现了PriorityOrdered或Ordered接口的普通BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法
// 在这个过程中可能会向BeanFactory中注册另外的BeanDefinitionRegistryPostProcessor，所以需要while，直到确定所有的BeanDefinitionRegistryPostProcessor都执行完了
// 在这个过程中注册的BeanDefinitionRegistryPostProcessor，所实现的PriorityOrdered或Ordered接口可能会不按顺序执行
// 比如 A注册了B和C,B又注册了D和E,那么B和C会按顺序执行，D和E也会按顺序执行，但是B、C、D、E整体不能保证是顺序执行
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();
}
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.
// 执行完BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry()方法后，
// 再执行BeanDefinitionRegistryPostProcessor的postProcessBeanFactory()方法
invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
// 执行手动添加的普通BeanFactoryPostProcessor的postProcessBeanFactory()方法
invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
}
else {
// Invoke factory processors registered with the context instance.
// 没有子类，直接执行BeanFactoryPostProcessor的postProcessBeanFactory()方法
invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
}
// 代码执到这里，就不会出现新的BeanDefinition！
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let the bean factory post-processors apply to them!
// 执行扫描出来的普通BeanFactoryPostProcessor
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<>();
// 先进行分类
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.
// 排序执行BeanFactory中实现了PriorityOrdered接口的BeanFactoryPostProcessor的postProcessBeanFactory()方法
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);
// Next, invoke the BeanFactoryPostProcessors that implement Ordered.
// 排序执行BeanFactory中实现了Ordered接口的BeanFactoryPostProcessor的postProcessBeanFactory()方法
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.
// 排序执行BeanFactory中其他的BeanFactoryPostProcessor的postProcessBeanFactory()方法
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...
// 清空缓存！
beanFactory.clearMetadataCache();
}
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