# Spring BeanFactoryPostProcessor - Author: [HuiFer](https://github.com/huifer) - 源码阅读仓库: [SourceHot-Spring](https://github.com/SourceHot/spring-framework-read) - 作用: 定制或修改`BeanDefinition`的属性 ## Demo ```java public class ChangeAttrBeanPostProcessor implements BeanFactoryPostProcessor { private Set attr; public ChangeAttrBeanPostProcessor() { attr = new HashSet<>(); } public Set getAttr() { return attr; } public void setAttr(Set attr) { this.attr = attr; } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { String[] beanDefinitionNames = beanFactory.getBeanDefinitionNames(); for (String beanName : beanDefinitionNames) { BeanDefinition beanDefinition = beanFactory.getBeanDefinition(beanName); StringValueResolver stringValueResolver = new StringValueResolver() { @Override public String resolveStringValue(String strVal) { if (attr.contains(strVal)) { return "隐藏属性"; } else { return strVal; } } }; BeanDefinitionVisitor visitor = new BeanDefinitionVisitor(stringValueResolver); visitor.visitBeanDefinition(beanDefinition); } } } ``` ```java public class BeanFactoryPostProcessorSourceCode { public static void main(String[] args) { ApplicationContext context = new ClassPathXmlApplicationContext("BeanFactoryPostProcessor-demo.xml"); Apple apple = context.getBean("apple", Apple.class); System.out.println(apple); } } ``` ```xml hc ``` ## 初始化 - `org.springframework.context.support.AbstractApplicationContext#refresh` ```JAVA invokeBeanFactoryPostProcessors(beanFactory); ``` ```JAVA protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) { 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())); } } ``` - `org.springframework.context.support.PostProcessorRegistrationDelegate#invokeBeanFactoryPostProcessors(org.springframework.beans.factory.config.ConfigurableListableBeanFactory, java.util.List)` ```JAVA public static void invokeBeanFactoryPostProcessors( ConfigurableListableBeanFactory beanFactory, List beanFactoryPostProcessors) { // Invoke BeanDefinitionRegistryPostProcessors first, if any. Set processedBeans = new HashSet<>(); // 判断是否为BeanDefinitionRegistry类 if (beanFactory instanceof BeanDefinitionRegistry) { BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory; // 存放 BeanFactoryPostProcessor List regularPostProcessors = new ArrayList<>(); // 存放 BeanDefinitionRegistryPostProcessor List registryProcessors = new ArrayList<>(); // 2.首先处理入参中的beanFactoryPostProcessors for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) { // 判断是否是BeanDefinitionRegistryPostProcessor if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) { BeanDefinitionRegistryPostProcessor registryProcessor = (BeanDefinitionRegistryPostProcessor) postProcessor; // registryProcessor.postProcessBeanDefinitionRegistry(registry); // BeanDefinitionRegistryPostProcessor 添加 // 执行 postProcessBeanFactory registryProcessors.add(registryProcessor); } // 这部分else 内容就是 BeanFactoryPostProcessor else { // BeanFactoryPostProcessor 添加 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 currentRegistryProcessors = new ArrayList<>(); // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered. /** * 调用实现{@link PriorityOrdered}\{@link BeanDefinitionRegistryPostProcessor} * todo: 2020年1月16日 解析方法 * {@link DefaultListableBeanFactory#getBeanNamesForType(java.lang.Class, boolean, boolean)} */ 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); } } // 排序Order sortPostProcessors(currentRegistryProcessors, beanFactory); registryProcessors.addAll(currentRegistryProcessors); invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry); currentRegistryProcessors.clear(); // 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(); // 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(); } // Now, invoke the postProcessBeanFactory callback of all processors handled so far. 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! // 配置文件中的 BeanFactoryPostProcessor 处理 String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false); // 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 // 处理过的跳过 } 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 orderedPostProcessors = new ArrayList<>(); for (String postProcessorName : orderedPostProcessorNames) { orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class)); } sortPostProcessors(orderedPostProcessors, beanFactory); invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory); // Finally, invoke all other BeanFactoryPostProcessors. // 配置文件中自定义的 BeanFactoryPostProcessor 注册 List nonOrderedPostProcessors = new ArrayList<>(); 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(); } ``` ![image-20200119085346675](../../../images/spring/image-20200119085346675.png) ![image-20200119085655734](../../../images/spring/image-20200119085655734.png) ## InstantiationAwareBeanPostProcessor ```java protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) { PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this); } ``` ```java public static void registerBeanPostProcessors( ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) { // 获取 BeanPostProcessor 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. // 获取数量 int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length; beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount)); // Separate between BeanPostProcessors that implement PriorityOrdered, // Ordered, and the rest. // BeanPostProcessor 通过PriorityOrdered保证顺序 List priorityOrderedPostProcessors = new ArrayList<>(); // MergedBeanDefinitionPostProcessor List internalPostProcessors = new ArrayList<>(); // 有序的 BeanPostProcessor List orderedPostProcessorNames = new ArrayList<>(); // 无序的 BeanPostProcessor List nonOrderedPostProcessorNames = new ArrayList<>(); for (String ppName : postProcessorNames) { if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); priorityOrderedPostProcessors.add(pp); // 类型判断放入相应的list 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. /** * 有{@link org.springframework.core.annotation.Order} 相关操作 */ sortPostProcessors(priorityOrderedPostProcessors, beanFactory); // 注册 BeanPostProcessor 和 PriorityOrdered 实现 registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors); // Next, register the BeanPostProcessors that implement Ordered. List orderedPostProcessors = new ArrayList<>(); for (String ppName : orderedPostProcessorNames) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); orderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } sortPostProcessors(orderedPostProcessors, beanFactory); // 注册 实现Order 和 BeanPostProcessor registerBeanPostProcessors(beanFactory, orderedPostProcessors); // Now, register all regular BeanPostProcessors. List nonOrderedPostProcessors = new ArrayList<>(); for (String ppName : nonOrderedPostProcessorNames) { BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class); nonOrderedPostProcessors.add(pp); if (pp instanceof MergedBeanDefinitionPostProcessor) { internalPostProcessors.add(pp); } } // 注册无序的 BeanPostProcessor registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors); // Finally, re-register all internal BeanPostProcessors. sortPostProcessors(internalPostProcessors, beanFactory); // 注册 MergedBeanDefinitionPostProcessor 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). // 添加 ApplicationListenerDetector beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); } ``` - 测试用 Bean ```java public class DemoInstantiationAwareBeanPostProcessor implements InstantiationAwareBeanPostProcessor { @Override public Object postProcessBeforeInstantiation(Class beanClass, String beanName) throws BeansException { System.out.println("init bean beanClass = " + beanClass.getSimpleName() + " beanName = " + beanName); return null; } } ``` - 按照笔者的注释,可以知道`DemoInstantiationAwareBeanPostProcessor` 这个类是一个无序 Bean ![image-20200119101026726](../../../images/spring/image-20200119101026726.png) ![image-20200119101017989](../../../images/spring/image-20200119101017989.png) - 注册方法信息截图 ![image-20200119101107820](../../../images/spring/image-20200119101107820.png) ### 使用阶段(调用阶段) 在`org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#createBean(java.lang.String, org.springframework.beans.factory.support.RootBeanDefinition, java.lang.Object[])`中有如下代码 ```JAVA Object bean = resolveBeforeInstantiation(beanName, mbdToUse); ``` - `org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#resolveBeforeInstantiation` ```JAVA @Nullable protected Object resolveBeforeInstantiation(String beanName, RootBeanDefinition mbd) { Object bean = null; if (!Boolean.FALSE.equals(mbd.beforeInstantiationResolved)) { // Make sure bean class is actually resolved at this point. if (!mbd.isSynthetic() && hasInstantiationAwareBeanPostProcessors()) { Class targetType = determineTargetType(beanName, mbd); if (targetType != null) { /** * 主要实现{@link org.springframework.beans.factory.config.InstantiationAwareBeanPostProcessor#postProcessBeforeInstantiation(java.lang.Class, java.lang.String)} */ bean = applyBeanPostProcessorsBeforeInstantiation(targetType, beanName); if (bean != null) { bean = applyBeanPostProcessorsAfterInitialization(bean, beanName); } } } mbd.beforeInstantiationResolved = (bean != null); } return bean; } ``` - `org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory#applyBeanPostProcessorsBeforeInstantiation` ```JAVA @Nullable protected Object applyBeanPostProcessorsBeforeInstantiation(Class beanClass, String beanName) { for (BeanPostProcessor bp : getBeanPostProcessors()) { if (bp instanceof InstantiationAwareBeanPostProcessor) { InstantiationAwareBeanPostProcessor ibp = (InstantiationAwareBeanPostProcessor) bp; // 调用自定义实现 Object result = ibp.postProcessBeforeInstantiation(beanClass, beanName); if (result != null) { return result; } } } return null; } ``` 这个地方已经可以看到`InstantiationAwareBeanPostProcessor`出现了,并且调用了方法`postProcessBeforeInstantiation`，此处就可以调用我们的自定义方法了 ![image-20200119101516591](../../../images/spring/image-20200119101516591.png)