1.BeanFactoryPostProcessors和BeanDefinitionRegistryPostProcessor的作用2.spring源码prepareBeanFactory(beanFactory)流程介绍3.spring源码prepareBeanFactory(beanFactory)源码解析4.总结 1.BeanFactoryPostProcessors和BeanDefinitionRegistryPostProcessor的作用
github源码地址（带正文）：https://github.com/su15967456...
spring源码执行流程图：
咱们点到这个办法里，大抵浏览一下代码，发现次要是围绕着这两个汇合进行操作：
简而言之：invokeBeanFactoryPostProcessors办法会把所有实现beanFactoryPostProcessor和BeanDefinitionRegistryPostProcessor的类进行实例化和调用。
咱们先来看一下beanFactoryPostProcessor的正文：
意思大抵为：在bean definitions全副加载结束，并且在初始化之前，beanFactoryPostProcessor能够对这些bd重写或者减少一些属性。
咱们再来看一下BeanDefinitionRegistryPostProcessor的正文：当bean definitions全副被加载结束，并且在初始化之前，BeanDefinitionRegistryPostProcessor减少一些额定的bean definition。
咱们得出结论：BeanDefinitionRegistryPostProcessor：能够用来减少新的bean DifinitionbeanFactoryPostProcessor：能够对bean Difinition的进行批改。
2.spring源码prepareBeanFactory(beanFactory)流程介绍
从整体的执行程序来看，这个办法的执行流程是这个样子的：
1)执行内部传进来的BeanFactoryPostProcessor类2)执行实现子类BeanDefinitionRegistryPostProcessor接口的类3)执行实现父类BeanFactoryPostProcessor接口的类
从执行每一步的BeanDefinitionRegistryPostProcessor或者BeanFactoryPostProcessor，又能够分为以下几个逻辑：
1)执行实现了PriorityOrdered（高优先级）的类2)执行实现了Ordered（有序）的类3)执行什么都没有实现的一般类
3.spring源码prepareBeanFactory(beanFactory)源码解析
public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) { // WARNING: Although it may appear that the body of this method can be easily // refactored to avoid the use of multiple loops and multiple lists, the use // of multiple lists and multiple passes over the names of processors is // intentional. We must ensure that we honor the contracts for PriorityOrdered // and Ordered processors. Specifically, we must NOT cause processors to be // instantiated (via getBean() invocations) or registered in the ApplicationContext // in the wrong order. // // Before submitting a pull request (PR) to change this method, please review the // list of all declined PRs involving changes to PostProcessorRegistrationDelegate // to ensure that your proposal does not result in a breaking change: // https://github.com/spring-projects/spring-framework/issues?q=PostProcessorRegistrationDelegate+is%3Aclosed+label%3A%22status%3A+declined%22 // Invoke BeanDefinitionRegistryPostProcessors first, if any. //无论是什么状况，先执行BeanDefinitionRegistryPostProcessors //将曾经执行的BFPP存储在processBean中，避免反复执行 Set<String> processedBeans = new HashSet<>(); //BeanDefinitionRegistry是对beanDefinition进行操作的类 // 判断beanFactory是不是 BeanDefinitionRegistry的实现，此处是DefaultListableBeanFactory,实现了BeanDefinitionRegistry接口，此处为true if (beanFactory instanceof BeanDefinitionRegistry) { //类型转换 BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; //此时要做一个辨别，BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子类 //BeanFactoryPostProcessor次要针对的对象是BeanFactory， //BeanDefinitionRegistryPostProcessor次要针对的对象是BeanDefinition //寄存BeanFactoryPostProcessor的汇合类 List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>(); //寄存BeanDefinitionRegistryPostProcessor的汇合 List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>(); //首先解决入参中的beanFactoryPostProcessors，遍历所有的beanFactoryPostProcessors for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { //如果是BeanDefinitionRegistryPostProcessor if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; //查找BeanDefinitionRegistryPostProcessor中的postProcessBeanDefinitionRegistry办法 registryProcessor.postProcessBeanDefinitionRegistry(registry); //增加到registryProcessors registryProcessors.add(registryProcessor); } else { 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. //用于保留本次要执行的BeanDefinitionRegistryPostProcessor List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>(); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. //调用所有实现PriorityOrdered接口的BeanDefinitionRegistryPostProcessor实现类 //找到所有实现BeanDefinitionRegistryPostProcessor接口bean的beanName String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); //遍历所有合乎规定的postProcessNames for (String ppName : postProcessorNames) { //检测是否实现了PriorityOrdered接口 if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { //获取名字对应的bean实例，增加到currentRegistryProcessor currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); //将要被执行的BFPP增加到processedBeans中，避免反复执行 processedBeans.add(ppName); } } //依照优先程序进行排序 sortPostProcessors(currentRegistryProcessors, beanFactory); //增加到registryProcessors中，用于最初执行postProcessBeanFactory办法 registryProcessors.addAll(currentRegistryProcessors); //遍历currentRegistryProcessors，执行postProcessBeanFactory办法 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup()); //执行结束后，清空 currentRegistryProcessors.clear(); // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered. //调用所有实现Ordered接口的BeanDefinitionRegistryPostProcessor实现类 //找到所有实现BeanDefinitionRegistryPostProcessor接口bean的beanName //为什么要从新获取 ： //下面调用invoke办法的时候，可能会新增一些 BeanDefinitionRegistryPostProcessor postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { //检测是否实现了Order接口，并且还未执行过程 if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) { //获取名字的bean实例，增加到currentRegistryProcessors currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); //增加到已执行过的processedBeans processedBeans.add(ppName); } } //依照优先程序进行排序 sortPostProcessors(currentRegistryProcessors, beanFactory); //增加到registryProcessors中，用于最初执行postProcessBeanFactory办法 registryProcessors.addAll(currentRegistryProcessors); //遍历currentRegistryProcessors，执行postProcessBeanFactory办法 invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry, beanFactory.getApplicationStartup()); //执行结束后，清空 currentRegistryProcessors.clear(); // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear. // 最初，调用剩下的BeanDefinitionRegistryPostProcessors，没有实现Order的 boolean reiterate = true; while (reiterate) { reiterate = false; //找出所有BeanDefinitionRegistryPostProcessors的接口类 postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false); for (String ppName : postProcessorNames) { //如果还未执行过BeanDefinitionRegistryPostProcessors if (!processedBeans.contains(ppName)) { currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)); processedBeans.add(ppName); //如果在中途过程中，可能会新增 BeanDefinitionRegistryPostProcessors，所以这里要为true 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postProcessBeanFactory invokeBeanFactoryPostProcessors(registryProcessors, beanFactory); invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory); } else { // Invoke factory processors registered with the context instance. invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory); } // Do not initialize FactoryBeans here: We need to leave all regular beans // uninitialized to let the bean factory post-processors apply to them! //获取实现BeanFactoryPostProcessor的所有类 //到目前为止，所有BeanDefinitionRegistryPostProcessor曾经全副实现结束了，接下来开始BeanFactoryPostProcessor的类的解决 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // 他们不反复执行是因为beanFactoryPostProcessor不会新增新Processor // Separate between BeanFactoryPostProcessors that implement PriorityOrdered, // Ordered, and the rest. //下面只执行了实现BeanDefinitionRegistryPostProcessor的postprocessor，并没有实现 //有priorityOrdered的PostProcessors汇合 List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>(); //有ordered的PostProcessors汇合 为什么上面两种存string，下面那种存类 //代码改掉还是能够运行的，猜想可能是省空间 List<String> orderedPostProcessorNames = new ArrayList<>(); //没有order的PostProcessors汇合 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. //依据priorityOrderedPostProcessors的汇合先排序，后执行 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(); }以上的几个逻辑，除了执行程序外，有几个重要的点：1）为什么执行子类BeanDefinitionRegistryPostProcessor的时候，每次都要从容器中从新获取类？因为实现BeanDefinitionRegistryPostProcessor的类能够减少新的bd，也就是说能够减少新的BeanDefinitionRegistryPostProcessor，所以每次都要从新获取。2）为什么执行父类BeanFactoryPostProcessor的时候，不必从新获取？因为父类BeanFactoryPostProcessor，不能减少新的bd，所以就不必从新获取了。3）
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