吃透Spring源码(十五):invokeBeanFactoryPostProcessors 执行流程

进入源码之前先来了解一下BeanFactoryPostProcessorBeanDefinitionRegistryPostProcessor

  • BeanFactoryPostProcessor:主要针对的操作对象是BeanFactory,主要是对BeanFactory的修改。
  • BeanDefinitionRegistryPostProcessor:是BeanFactoryPostProcessor的子接口,主要针对的操作对象是BeanDefinition
public interface BeanFactoryPostProcessor {
   
     

	void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException;

}

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
   
     

	void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException;

}

refresh()方法

public abstract class AbstractApplicationContext extends DefaultResourceLoader
		implements ConfigurableApplicationContext {
   
     
    @Override
	public void refresh() throws BeansException, IllegalStateException {
   
     
		synchronized (this.startupShutdownMonitor) {
   
     
			// Prepare this context for refreshing.
			/**
			 * 前戏,做容器刷新前的准备工作
			 * 1、设置容器的启动时间
			 * 2、设置活跃状态为true
			 * 3、设置关闭状态为false
			 * 4、获取Environment对象,并加载当前系统的属性值到Environment对象中
			 * 5、准备监听器和事件的集合对象,默认为空的集合
			 */

			prepareRefresh();

			// Tell the subclass to refresh the internal bean factory.
			// 创建容器对象:DefaultListableBeanFactory
			// 加载xml配置文件的属性值到当前工厂中,最重要的就是BeanDefinition
			ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();

			// Prepare the bean factory for use in this context.
			// beanFactory的准备工作,对各种属性进行填充
			prepareBeanFactory(beanFactory);

			try {
   
     
				// Allows post-processing of the bean factory in context subclasses.
				// 子类覆盖方法做额外的处理,此处我们自己一般不做任何扩展工作,但是可以查看web中的代码,是有具体实现的
				postProcessBeanFactory(beanFactory);

				// Invoke factory processors registered as beans in the context.
				// 调用各种beanFactory处理器
				invokeBeanFactoryPostProcessors(beanFactory);

				// Register bean processors that intercept bean creation.
				// 注册bean处理器,这里只是注册功能,真正调用的是getBean方法
				registerBeanPostProcessors(beanFactory);

				// Initialize message source for this context.
				// 为上下文初始化message源,即不同语言的消息体,国际化处理,在springmvc的时候通过国际化的代码重点讲
				initMessageSource();

				// Initialize event multicaster for this context.
				// 初始化事件监听多路广播器
				initApplicationEventMulticaster();

				// Initialize other special beans in specific context subclasses.
				// 留给子类来初始化其他的bean
				onRefresh();

				// Check for listener beans and register them.
				// 在所有注册的bean中查找listener bean,注册到消息广播器中
				registerListeners();

				// Instantiate all remaining (non-lazy-init) singletons.
				// 初始化剩下的单实例(非懒加载的)
				finishBeanFactoryInitialization(beanFactory);

				// Last step: publish corresponding event.
				// 完成刷新过程,通知生命周期处理器lifecycleProcessor刷新过程,同时发出ContextRefreshEvent通知别人
				finishRefresh();
			}

			catch (BeansException ex) {
   
     
				if (logger.isWarnEnabled()) {
   
     
					logger.warn("Exception encountered during context initialization - " +
							"cancelling refresh attempt: " + ex);
				}

				// Destroy already created singletons to avoid dangling resources.
				// 为防止bean资源占用,在异常处理中,销毁已经在前面过程中生成的单件bean
				destroyBeans();

				// Reset 'active' flag.
				// 重置active标志
				cancelRefresh(ex);

				// Propagate exception to caller.
				throw ex;
			}

			finally {
   
     
				// Reset common introspection caches in Spring's core, since we
				// might not ever need metadata for singleton beans anymore...
				resetCommonCaches();
			}
		}
	}
}

invokeBeanFactoryPostProcessors()方法

public abstract class AbstractApplicationContext extends DefaultResourceLoader
		implements ConfigurableApplicationContext {
   
     	
    
    /**
	 * 用来存放beanFactory的后置处理器集合
	 */
	private final List<BeanFactoryPostProcessor> beanFactoryPostProcessors = new ArrayList<>();
    
    public List<BeanFactoryPostProcessor> getBeanFactoryPostProcessors() {
   
     
		return this.beanFactoryPostProcessors;
	}
    
	protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
   
     
		// 获取到当前应用程序上下文的beanFactoryPostProcessors变量的值,并且实例化调用执行所有已经注册的beanFactoryPostProcessor
		// 默认情况下,通过getBeanFactoryPostProcessors()来获取已经注册的BFPP,但是默认是空的,那么问题来了,如果你想扩展,怎么进行扩展工作?
		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()));
		}
	}
}

具体处理方法

	public static void invokeBeanFactoryPostProcessors(
            ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {
   
     

        // 无论是什么情况,优先执行BeanDefinitionRegistryPostProcessors
        // 将已经执行过的BFPP存储在processedBeans中,防止重复执行
        Set<String> processedBeans = new HashSet<>();

        // 判断beanfactory是否是BeanDefinitionRegistry类型,此处是DefaultListableBeanFactory,实现了BeanDefinitionRegistry接口,所以为true
        if (beanFactory instanceof BeanDefinitionRegistry) {
   
     
            // 类型转换
            BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
            // 此处希望大家做一个区分,两个接口是不同的,BeanDefinitionRegistryPostProcessor是BeanFactoryPostProcessor的子集
            // BeanFactoryPostProcessor主要针对的操作对象是BeanFactory,而BeanDefinitionRegistryPostProcessor主要针对的操作对象是BeanDefinition
            // 存放BeanFactoryPostProcessor的集合
            List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
            // 存放BeanDefinitionRegistryPostProcessor的集合
            List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

            // 首先处理入参中的beanFactoryPostProcessors,遍历所有的beanFactoryPostProcessors,将BeanDefinitionRegistryPostProcessor
            // 和BeanFactoryPostProcessor区分开
            for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
   
     
                // 如果是BeanDefinitionRegistryPostProcessor
                if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
   
     
                    BeanDefinitionRegistryPostProcessor registryProcessor =
                            (BeanDefinitionRegistryPostProcessor) postProcessor;
                    // 直接执行BeanDefinitionRegistryPostProcessor接口中的postProcessBeanDefinitionRegistry方法
                    registryProcessor.postProcessBeanDefinitionRegistry(registry);
                    // 添加到registryProcessors,用于后续执行postProcessBeanFactory方法
                    registryProcessors.add(registryProcessor);
                } else {
   
     
                    // 否则,只是普通的BeanFactoryPostProcessor,添加到regularPostProcessors,用于后续执行postProcessBeanFactory方法
                    regularPostProcessors.add(postProcessor);
                }
            }

            
            // 用于保存本次要执行的BeanDefinitionRegistryPostProcessor
            List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

            // 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);
            // 遍历处理所有符合规则的postProcessorNames
            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,添加到currentRegistryProcessors中
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    // 将要被执行的BFPP名称添加到processedBeans,避免后续重复执行
                    processedBeans.add(ppName);
                }
            }
            // 按照优先级进行排序操作
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 添加到registryProcessors中,用于最后执行postProcessBeanFactory方法
            registryProcessors.addAll(currentRegistryProcessors);
            // 遍历currentRegistryProcessors,执行postProcessBeanDefinitionRegistry方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 执行完毕之后,清空currentRegistryProcessors
            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,
            // 此处需要重复查找的原因在于上面的执行过程中可能会新增其他的BeanDefinitionRegistryPostProcessor
            postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
            for (String ppName : postProcessorNames) {
   
     
                // 检测是否实现了Ordered接口,并且还未执行过
                if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
   
     
                    // 获取名字对应的bean实例,添加到currentRegistryProcessors中
                    currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                    // 将要被执行的BFPP名称添加到processedBeans,避免后续重复执行
                    processedBeans.add(ppName);
                }
            }
            // 按照优先级进行排序操作
            sortPostProcessors(currentRegistryProcessors, beanFactory);
            // 添加到registryProcessors中,用于最后执行postProcessBeanFactory方法
            registryProcessors.addAll(currentRegistryProcessors);
            // 遍历currentRegistryProcessors,执行postProcessBeanDefinitionRegistry方法
            invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
            // 执行完毕之后,清空currentRegistryProcessors
            currentRegistryProcessors.clear();

            // Finally, invoke all other BeanDefinitionRegistryPostProcessors until no further ones appear.
            // 最后,调用所有剩下的BeanDefinitionRegistryPostProcessors
            boolean reiterate = true;
            while (reiterate) {
   
     
                reiterate = false;
                // 找出所有实现BeanDefinitionRegistryPostProcessor接口的类
                postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
                // 遍历执行
                for (String ppName : postProcessorNames) {
   
     
                    // 跳过已经执行过的BeanDefinitionRegistryPostProcessor
                    if (!processedBeans.contains(ppName)) {
   
     
                        // 获取名字对应的bean实例,添加到currentRegistryProcessors中
                        currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                        // 将要被执行的BFPP名称添加到processedBeans,避免后续重复执行
                        processedBeans.add(ppName);
                        reiterate = true;
                    }
                }
                // 按照优先级进行排序操作
                sortPostProcessors(currentRegistryProcessors, beanFactory);
                // 添加到registryProcessors中,用于最后执行postProcessBeanFactory方法
                registryProcessors.addAll(currentRegistryProcessors);
                // 遍历currentRegistryProcessors,执行postProcessBeanDefinitionRegistry方法
                invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);
                // 执行完毕之后,清空currentRegistryProcessors
                currentRegistryProcessors.clear();
            }

            // Now, invoke the postProcessBeanFactory callback of all processors handled so far.
            // 调用所有BeanDefinitionRegistryPostProcessor的postProcessBeanFactory方法
            invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);
            // 最后,调用入参beanFactoryPostProcessors中的普通BeanFactoryPostProcessor的postProcessBeanFactory方法
            invokeBeanFactoryPostProcessors(regularPostProcessors, beanFactory);
        } else {
   
     
            // Invoke factory processors registered with the context instance.
            // 如果beanFactory不归属于BeanDefinitionRegistry类型,那么直接执行postProcessBeanFactory方法
            invokeBeanFactoryPostProcessors(beanFactoryPostProcessors, beanFactory);
        }

        // 到这里为止,入参beanFactoryPostProcessors和容器中的所有BeanDefinitionRegistryPostProcessor已经全部处理完毕,下面开始处理容器中
        // 所有的BeanFactoryPostProcessor
        // 可能会包含一些实现类,只实现了BeanFactoryPostProcessor,并没有实现BeanDefinitionRegistryPostProcessor接口

        // 找到所有实现BeanFactoryPostProcessor接口的类
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanFactoryPostProcessor.class, true, false);

        // 用于存放实现了PriorityOrdered接口的BeanFactoryPostProcessor
        List<BeanFactoryPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
        // 用于存放实现了Ordered接口的BeanFactoryPostProcessor的beanName
//		List<String> orderedPostProcessorNames = new ArrayList<>();
        List<BeanFactoryPostProcessor> orderedPostProcessor = new ArrayList<>();
        // 用于存放普通BeanFactoryPostProcessor的beanName
//		List<String> nonOrderedPostProcessorNames = new ArrayList<>();
        List<BeanFactoryPostProcessor> nonOrderedPostProcessorNames = new ArrayList<>();
        // 遍历postProcessorNames,将BeanFactoryPostProcessor按实现PriorityOrdered、实现Ordered接口、普通三种区分开
        for (String ppName : postProcessorNames) {
   
     
            // 跳过已经执行过的BeanFactoryPostProcessor
            if (processedBeans.contains(ppName)) {
   
     
                // skip - already processed in first phase above
            }
            // 添加实现了PriorityOrdered接口的BeanFactoryPostProcessor到priorityOrderedPostProcessors
            else if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
   
     
                priorityOrderedPostProcessors.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
            // 添加实现了Ordered接口的BeanFactoryPostProcessor的beanName到orderedPostProcessorNames
            else if (beanFactory.isTypeMatch(ppName, Ordered.class)) {
   
     
//				orderedPostProcessorNames.add(ppName);
                orderedPostProcessor.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            } else {
   
     
                // 添加剩下的普通BeanFactoryPostProcessor的beanName到nonOrderedPostProcessorNames
//				nonOrderedPostProcessorNames.add(ppName);
                nonOrderedPostProcessorNames.add(beanFactory.getBean(ppName, BeanFactoryPostProcessor.class));
            }
        }

        // First, invoke the BeanFactoryPostProcessors that implement PriorityOrdered.
        // 对实现了PriorityOrdered接口的BeanFactoryPostProcessor进行排序
        sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
        // 遍历实现了PriorityOrdered接口的BeanFactoryPostProcessor,执行postProcessBeanFactory方法
        invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

        // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
        // 创建存放实现了Ordered接口的BeanFactoryPostProcessor集合
//		List<BeanFactoryPostProcessor> orderedPostProcessors = new ArrayList<>(orderedPostProcessorNames.size());
        // 遍历存放实现了Ordered接口的BeanFactoryPostProcessor名字的集合
//		for (String postProcessorName : orderedPostProcessorNames) {
   
     
        // 将实现了Ordered接口的BeanFactoryPostProcessor添加到集合中
//			orderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
//		}
        // 对实现了Ordered接口的BeanFactoryPostProcessor进行排序操作
//		sortPostProcessors(orderedPostProcessors, beanFactory);
        sortPostProcessors(orderedPostProcessor, beanFactory);
        // 遍历实现了Ordered接口的BeanFactoryPostProcessor,执行postProcessBeanFactory方法
//		invokeBeanFactoryPostProcessors(orderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(orderedPostProcessor, beanFactory);

        // Finally, invoke all other BeanFactoryPostProcessors.
        // 最后,创建存放普通的BeanFactoryPostProcessor的集合
//		List<BeanFactoryPostProcessor> nonOrderedPostProcessors = new ArrayList<>(nonOrderedPostProcessorNames.size());
        // 遍历存放实现了普通BeanFactoryPostProcessor名字的集合
//		for (String postProcessorName : nonOrderedPostProcessorNames) {
   
     
        // 将普通的BeanFactoryPostProcessor添加到集合中
//			nonOrderedPostProcessors.add(beanFactory.getBean(postProcessorName, BeanFactoryPostProcessor.class));
//		}
        // 遍历普通的BeanFactoryPostProcessor,执行postProcessBeanFactory方法
//		invokeBeanFactoryPostProcessors(nonOrderedPostProcessors, beanFactory);
        invokeBeanFactoryPostProcessors(nonOrderedPostProcessorNames, beanFactory);

        // Clear cached merged bean definitions since the post-processors might have
        // modified the original metadata, e.g. replacing placeholders in values...
        // 清除元数据缓存(mergeBeanDefinitions、allBeanNamesByType、singletonBeanNameByType)
        // 因为后置处理器可能已经修改了原始元数据,例如,替换值中的占位符
        beanFactory.clearMetadataCache();
    }

  1. 先处理参数中传过来的beanFactoryPostProcessors中的 BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry()方法
  2. 处理容器中的指定BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry()方法,按照优先级排序执行
    3、 重复执行步骤2,有可能在执行2的过程中又加入了新的BeanDefinitionRegistryPostProcessor
  3. 执行剩余的所有普通的没有实现优先级接口的BeanDefinitionRegistryPostProcessor#postProcessBeanDefinitionRegistry()方法
  4. 执行入参beanFactoryPostProcessors中的普通BeanFactoryPostProcessor#postProcessBeanFactory()方法
    6、 遍历实现了PriorityOrdered接口的BeanFactoryPostProcessor,执行postProcessBeanFactory方法;
    7、 遍历实现了Ordered接口的BeanFactoryPostProcessor,执行postProcessBeanFactory方法;
    8、 遍历普通的BeanFactoryPostProcessor,执行postProcessBeanFactory方法;

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