文章目录
- Pre
- org.springframework.beans.factory.config.BeanFactoryPostProcessor
- 源码探究
- 1 是否实现BeanDefinitionRegistryPostProcessor 接口，分别写入集合
- 2 处理实现了的PriorityOrdered和 BeanDefinitionRegistryPostProcessors 的 bean
- 3. 处理实现了的Ordered和BeanDefinitionRegistryPostProcessors 的 bean
- 4 处理其他实现了BeanDefinitionRegistryPostProcessor的bean
- 5 invokeBeanFactoryPostProcessors
- 6 除了试下BeanDefinitionRegistryPostProcessor之外的其他 实现了BeanFactoryPostProcessor接口的bean 分类
- 7 处理 PriorityOrdered ，invokeBeanDefinitionRegistryPostProcessors
- 8 处理 Ordered ，invokeBeanDefinitionRegistryPostProcessors
- 9 处理剩下的 ，invokeBeanDefinitionRegistryPostProcessors
- 10 invokeBeanDefinitionRegistryPostProcessors & invokeBeanFactoryPostProcessors 分析
- BeanFactoryPostProcessor的处理流程
- 扩展方式
Pre
Spring Boot – 扩展接口一览
org.springframework.beans.factory.config.BeanFactoryPostProcessor
这个接口是beanFactory的扩展接口，调用时机在spring在读取beanDefinition信息之后，实例化bean之前。
在这个时机，用户可以通过实现这个扩展接口来自行处理一些东西，比如修改已经注册的beanDefinition的元信息
package org.springframework.beans.factory.config;import org.springframework.beans.BeansException;/** * Factory hook that allows for custom modification of an application context's * bean definitions, adapting the bean property values of the context's underlying * bean factory. * * Useful for custom config files targeted at system administrators that * override bean properties configured in the application context. See * {@link PropertyResourceConfigurer} and its concrete implementations for * out-of-the-box solutions that address such configuration needs. * *
A {@code BeanFactoryPostProcessor} may interact with and modify bean * definitions, but never bean instances. Doing so may cause premature bean * instantiation, violating the container and causing unintended side-effects. * If bean instance interaction is required, consider implementing * {@link BeanPostProcessor} instead. * *
Registration
* An {@code ApplicationContext} auto-detects {@code BeanFactoryPostProcessor} * beans in its bean definitions and applies them before any other beans get created. * A {@code BeanFactoryPostProcessor} may also be registered programmatically * with a {@code ConfigurableApplicationContext}. * *
Ordering
* {@code BeanFactoryPostProcessor} beans that are autodetected in an * {@code ApplicationContext} will be ordered according to * {@link org.springframework.core.PriorityOrdered} and * {@link org.springframework.core.Ordered} semantics. In contrast, * {@code BeanFactoryPostProcessor} beans that are registered programmatically * with a {@code ConfigurableApplicationContext} will be applied in the order of * registration; any ordering semantics expressed through implementing the * {@code PriorityOrdered} or {@code Ordered} interface will be ignored for * programmatically registered post-processors. Furthermore, the * {@link org.springframework.core.annotation.Order @Order} annotation is not * taken into account for {@code BeanFactoryPostProcessor} beans. * * @author Juergen Hoeller * @author Sam Brannen * @since 06.07.2003 * @see BeanPostProcessor * @see PropertyResourceConfigurer */
@FunctionalInterfacepublic 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;}spring容器初始化时，从资源中读取到bean的相关定义后，保存在beanFactory的成员变量中（DefaultListableBeanFactory#beanDefinitionMap）
private final Map<String, BeanDefinition> beanDefinitionMap = new ConcurrentHashMap<>(256);实例化bean的操作就是依据这些BeanDefinition来做的。
在实例化之前，spring允许我们通过自定义扩展来改变bean的定义，定义一旦变了，后面的实例也就变了，而beanFactory后置处理器BeanFactoryPostProcessor就是用来改变bean定义的。
源码探究
AbstractApplicationContext#refresh 继续走起
继续
// Invoke factory processors registered as beans in the context.invokeBeanFactoryPostProcessors(beanFactory);主要功能是： 找出所有beanFactory后置处理器，并且调用这些处理器来改变bean的定义
继续 org.springframework.context.support.AbstractApplicationContext#invokeBeanFactoryPostProcessors
/** * Instantiate and invoke all registered BeanFactoryPostProcessor beans, * respecting explicit order if given. * Must be called before singleton instantiation. */
protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());.......我们重点关注PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors
PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors());代码比较长，我们逐段看一下
1 是否实现BeanDefinitionRegistryPostProcessor 接口，分别写入集合
for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {BeanDefinitionRegistryPostProcessor registryProcessor =(BeanDefinitionRegistryPostProcessor) postProcessor;registryProcessor.postProcessBeanDefinitionRegistry(registry);registryProcessors.add(registryProcessor);}else {regularPostProcessors.add(postProcessor);}}遍历入参 beanFactoryPostProcessors ， 是否实现了BeanDefinitionRegistryPostProcessor，分别放入两个集合：registryProcessors和regularPostProcessors；
2 处理实现了的PriorityOrdered和 BeanDefinitionRegistryPostProcessors 的 bean
// 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, beanFactory.getApplicationStartup());currentRegistryProcessors.clear();找出所有实现了BeanDefinitionRegistryPostProcessor接口和PriorityOrdered接口的bean，放入registryProcessors集合，根据PriorityOrdered接口来排序，然后这些bean会被invokeBeanDefinitionRegistryPostProcessors方法执行；
3. 处理实现了的Ordered和BeanDefinitionRegistryPostProcessors 的 bean
// 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, beanFactory.getApplicationStartup());currentRegistryProcessors.clear();找出所有实现了BeanDefinitionRegistryPostProcessor接口和Ordered接口的bean，放入registryProcessors集合，根据Ordered接口来排序，然后这些bean会被invokeBeanDefinitionRegistryPostProcessors方法执行；
4 处理其他实现了BeanDefinitionRegistryPostProcessor的bean
// 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, beanFactory.getApplicationStartup());currentRegistryProcessors.clear();}对于那些实现了BeanDefinitionRegistryPostProcessor接口，但是没有实现PriorityOrdered和Ordered的bean也被找出来，然后这些bean会被invokeBeanDefinitionRegistryPostProcessors方法执行
5 invokeBeanFactoryPostProcessors
// Now, invoke the postProcessBeanFactory callback of all processors handled so far.invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);6 除了试下BeanDefinitionRegistryPostProcessor之外的其他 实现了BeanFactoryPostProcessor接口的bean 分类
// 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);}}找出实现了BeanFactoryPostProcessor接口的bean，注意这里已将前面实现了BeanDefinitionRegistryPostProcessor接口的bean给剔除了
if (processedBeans.contains(ppName)) {// skip - already processed in first phase above}将这些bean分为三类：
- 实现了PriorityOrdered接口的放入priorityOrderedPostProcessors，
- 实现了Ordered接口的放入orderedPostProcessorNames，
- 其他的放入nonOrderedPostProcessorNames，这段代码是关键，自定义的实现BeanFactoryPostProcessor接口的bean就会在此处被查找出来。
7 处理 PriorityOrdered ，invokeBeanDefinitionRegistryPostProcessors
// First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.sortPostProcessors(priorityOrderedPostProcessors, beanFactory);invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);8 处理 Ordered ，invokeBeanDefinitionRegistryPostProcessors
// 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);9 处理剩下的 ，invokeBeanDefinitionRegistryPostProcessors
// 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);10 invokeBeanDefinitionRegistryPostProcessors & invokeBeanFactoryPostProcessors 分析
从上面的分析可以发现，所有实现了BeanFactoryPostProcessor接口的bean，都被作为入参，然后调用了invokeBeanDefinitionRegistryPostProcessors或者invokeBeanFactoryPostProcessors方法去处理
/** * Invoke the given BeanDefinitionRegistryPostProcessor beans. */private static void invokeBeanDefinitionRegistryPostProcessors(Collection<" />