计算机网站建设招聘,贵州城市和城乡建设官方网站,网站建设新手教程视频,如何自学广告设计BeanPostProcessors是Spring框架中的一个扩展机制#xff0c;它允许开发人员在Spring容器实例化、配置和初始化Bean的过程中干预和定制化。BeanPostProcessor接口定义了两个方法#xff1a;postProcessBeforeInitialization和postProcessAfterInitialization#xff0c;分别…BeanPostProcessors是Spring框架中的一个扩展机制它允许开发人员在Spring容器实例化、配置和初始化Bean的过程中干预和定制化。BeanPostProcessor接口定义了两个方法postProcessBeforeInitialization和postProcessAfterInitialization分别在Bean初始化之前和之后被调用。 BeanPostProcessors的作用是在Bean的初始化过程中提供额外的处理逻辑。通过实现BeanPostProcessor接口并注册到Spring容器中开发人员可以在Bean实例化后的早期和后期阶段对Bean进行修改、增强或执行其他自定义逻辑。这样可以实现很多功能如属性注入、AOP代理、资源初始化等。 猜测 入口是在AbstractApplicationContext的refresh方法中在方法中调用了registerBeanPostProcessors(beanFactory)从字面意思来说就是注册BeanPostProcessorsBeanPostProcessor具体做什么用的上面也有介绍本章就分析一下这个注册做了哪些事情。 分析 老规矩从入口的注释开始这个方法就是实例化和注册所有的BeanPostProcessor尊重期望的排序如果有给出的话这个方法必须在我们应用bean实力化之前被调用。 /*** Instantiate and register all BeanPostProcessor beans,* respecting explicit order if given.* pMust be called before any instantiation of application beans.*/ protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this); }方法实际调用的是PostProcessorRegistrationDelegate类中的registerBeanPostProcessors方法如果调用参数的详细入下截图所示 PostProcessorRegistrationDelegate 这个类中的方法其实就是整个代码的核心接下来我们继续用拆解的方式来进行分析下面是其所有的代码块。 public static void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {// 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?qPostProcessorRegistrationDelegateis%3Aclosedlabel%3A%22status%3Adeclined%22String[] 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.int beanProcessorTargetCount beanFactory.getBeanPostProcessorCount() 1 postProcessorNames.length;beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));// Separate between BeanPostProcessors that implement PriorityOrdered,// Ordered, and the rest.ListBeanPostProcessor priorityOrderedPostProcessors new ArrayList();ListBeanPostProcessor internalPostProcessors new ArrayList();ListString orderedPostProcessorNames new ArrayList();ListString 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.sortPostProcessors(priorityOrderedPostProcessors, beanFactory);registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);// Next, register the BeanPostProcessors that implement Ordered.ListBeanPostProcessor 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);}}sortPostProcessors(orderedPostProcessors, beanFactory);registerBeanPostProcessors(beanFactory, orderedPostProcessors);// Now, register all regular BeanPostProcessors.ListBeanPostProcessor 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);}}registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);// Finally, re-register all internal BeanPostProcessors.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).beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext)); }步骤一 直接通过类型去获取所有的BeanPostProcessor的BeanNames存在postProcessorNames数组中。 String[] postProcessorNames beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);步骤二 注册一个名为BeanPostProcessorChecker的BeanPostProcessor并将其添加到beanFactory中。 具体分析如下 获取已注册的BeanPostProcessor数量 int beanProcessorTargetCount beanFactory.getBeanPostProcessorCount();这行代码获取已经注册到beanFactory的BeanPostProcessor的数量。 计算新的BeanPostProcessor的目标数量 beanProcessorTargetCount beanProcessorTargetCount 1 postProcessorNames.length;在已有的BeanPostProcessor数量基础上加上1表示新注册的BeanPostProcessorChecker以及postProcessorNames的长度表示后续要注册的BeanPostProcessor的数量计算出新的目标数量。 创建并注册BeanPostProcessorChecker beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));创建一个名为BeanPostProcessorChecker的BeanPostProcessor实例并将其添加到beanFactory中。BeanPostProcessorChecker是一个自定义的BeanPostProcessor它在BeanPostProcessor实例化期间检查并记录信息。具体来说当创建BeanPostProcessor期间创建了一个Bean即一个Bean不符合所有BeanPostProcessor的处理条件时BeanPostProcessorChecker会记录一个信息日志。 步骤三 对已注册的BeanPostProcessor进行分类并按照优先级顺序注册到beanFactory中。 创建用于存储实现PriorityOrdered接口的BeanPostProcessor的列表 ListBeanPostProcessor priorityOrderedPostProcessors new ArrayList();创建一个名为priorityOrderedPostProcessors的列表用于存储实现了PriorityOrdered接口的BeanPostProcessor。 创建用于存储内部BeanPostProcessor的列表 ListBeanPostProcessor internalPostProcessors new ArrayList();创建一个名为internalPostProcessors的列表用于存储内部的BeanPostProcessor。 创建用于存储实现Ordered接口的BeanPostProcessor名称的列表 ListString orderedPostProcessorNames new ArrayList();创建一个名为orderedPostProcessorNames的列表用于存储实现了Ordered接口的BeanPostProcessor的名称。 创建用于存储未实现Ordered接口的BeanPostProcessor名称的列表 ListString nonOrderedPostProcessorNames new ArrayList();创建一个名为nonOrderedPostProcessorNames的列表用于存储未实现Ordered接口的BeanPostProcessor的名称。 遍历已注册的BeanPostProcessor名称列表根据其类型进行分类 for (String ppName : postProcessorNames) {if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {// BeanPostProcessor实现了PriorityOrdered接口BeanPostProcessor pp beanFactory.getBean(ppName, BeanPostProcessor.class);priorityOrderedPostProcessors.add(pp);if (pp instanceof MergedBeanDefinitionPostProcessor) {// 内部的BeanPostProcessorinternalPostProcessors.add(pp);}}else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {// BeanPostProcessor实现了Ordered接口orderedPostProcessorNames.add(ppName);}else {// 未实现Ordered接口的BeanPostProcessornonOrderedPostProcessorNames.add(ppName);} }遍历已注册的BeanPostProcessor名称列表postProcessorNames根据名称对应的BeanPostProcessor的类型进行分类。如果BeanPostProcessor实现了PriorityOrdered接口则将其添加到priorityOrderedPostProcessors列表中如果是MergedBeanDefinitionPostProcessor的实例则也添加到internalPostProcessors列表中如果实现了Ordered接口则将其名称添加到orderedPostProcessorNames列表中否则将其名称添加到nonOrderedPostProcessorNames列表中。 对实现PriorityOrdered接口的BeanPostProcessor进行排序 sortPostProcessors(priorityOrderedPostProcessors, beanFactory);调用sortPostProcessors方法对priorityOrderedPostProcessors列表中的BeanPostProcessor进行排序按照优先级顺序进行排序。 注册实现PriorityOrdered接口的BeanPostProcessor到beanFactory中 registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);调用registerBeanPostProcessors方法将priorityOrderedPostProcessors列表中的BeanPostProcessor注册到beanFactory中。 步骤四 实现了Ordered接口的BeanPostProcessor到beanFactory中。 创建用于存储实现Ordered接口的BeanPostProcessor的列表 ListBeanPostProcessor orderedPostProcessors new ArrayList(orderedPostProcessorNames.size());创建一个名为orderedPostProcessors的列表用于存储实现了Ordered接口的BeanPostProcessor。 遍历实现了Ordered接口的BeanPostProcessor的名称列表并将它们实例化并添加到orderedPostProcessors列表中 for (String ppName : orderedPostProcessorNames) {BeanPostProcessor pp beanFactory.getBean(ppName, BeanPostProcessor.class);orderedPostProcessors.add(pp);if (pp instanceof MergedBeanDefinitionPostProcessor) {// 内部的BeanPostProcessorinternalPostProcessors.add(pp);} }遍历实现了Ordered接口的BeanPostProcessor的名称列表orderedPostProcessorNames通过beanFactory.getBean方法实例化每个BeanPostProcessor并将其添加到orderedPostProcessors列表中。如果BeanPostProcessor是MergedBeanDefinitionPostProcessor的实例则也添加到internalPostProcessors列表中。 对实现Ordered接口的BeanPostProcessor进行排序 sortPostProcessors(orderedPostProcessors, beanFactory);调用sortPostProcessors方法对orderedPostProcessors列表中的BeanPostProcessor进行排序按照Ordered接口的顺序进行排序。 注册实现Ordered接口的BeanPostProcessor到beanFactory中 registerBeanPostProcessors(beanFactory, orderedPostProcessors);调用registerBeanPostProcessors方法将orderedPostProcessors列表中的BeanPostProcessor注册到beanFactory中。 步骤五 注册剩余的未实现Ordered接口的BeanPostProcessor并重新注册内部的BeanPostProcessor。 创建用于存储未实现Ordered接口的BeanPostProcessor的列表 ListBeanPostProcessor nonOrderedPostProcessors new ArrayList(nonOrderedPostProcessorNames.size());创建一个名为nonOrderedPostProcessors的列表用于存储未实现Ordered接口的BeanPostProcessor。 遍历未实现Ordered接口的BeanPostProcessor的名称列表并将它们实例化并添加到nonOrderedPostProcessors列表中 for (String ppName : nonOrderedPostProcessorNames) {BeanPostProcessor pp beanFactory.getBean(ppName, BeanPostProcessor.class);nonOrderedPostProcessors.add(pp);if (pp instanceof MergedBeanDefinitionPostProcessor) {// 内部的BeanPostProcessorinternalPostProcessors.add(pp);} }遍历未实现Ordered接口的BeanPostProcessor的名称列表nonOrderedPostProcessorNames通过beanFactory.getBean方法实例化每个BeanPostProcessor并将其添加到nonOrderedPostProcessors列表中。如果BeanPostProcessor是MergedBeanDefinitionPostProcessor的实例则也添加到internalPostProcessors列表中。 注册未实现Ordered接口的BeanPostProcessor到beanFactory中 registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);调用registerBeanPostProcessors方法将nonOrderedPostProcessors列表中的BeanPostProcessor注册到beanFactory中。 对内部的BeanPostProcessor进行排序 sortPostProcessors(internalPostProcessors, beanFactory);调用sortPostProcessors方法对internalPostProcessors列表中的BeanPostProcessor进行排序。 重新注册内部的BeanPostProcessor到beanFactory中 registerBeanPostProcessors(beanFactory, internalPostProcessors);调用registerBeanPostProcessors方法将internalPostProcessors列表中的BeanPostProcessor重新注册到beanFactory中。 重新注册用于检测内部Bean作为ApplicationListeners的后处理器 beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));创建一个ApplicationListenerDetector的实例并将其作为BeanPostProcessor添加到beanFactory中。这个后处理器用于检测内部Bean是否为ApplicationListeners并将其移动到处理器链的末尾以便在处理代理等情况时能够正确拾取内部Bean。