Spring5源码解析4-refresh方法之invokeBeanFacto…

2019-10-12 08:23:42来源:博客园 阅读 ()

新老客户大回馈,云服务器低至5折

Spring5源码解析4-refresh方法之invokeBeanFactoryPostProcessors

invokeBeanFactoryPostProcessors(beanFactory);方法源码如下:

protected void invokeBeanFactoryPostProcessors(ConfigurableListableBeanFactory beanFactory) {
    // getBeanFactoryPostProcessors 获取的是 this.beanFactoryPostProcessors;
    //this.beanFactoryPostProcessors 只能通过 AbstractApplicationContext.addBeanFactoryPostProcessor 方法添加
    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()));
    }
}

getBeanFactoryPostProcessors()方法获取的是AbstractApplicationContext#beanFactoryPostProcessors这个成员变量。

这个成员变量只能通过代码中手动编码调用AbstractApplicationContext#addBeanFactoryPostProcessor方法来添加新的元素。很明显,我们这里为空。

invokeBeanFactoryPostProcessors(beanFactory)方法的主要的逻辑在PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors方法中:

//PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(beanFactory, getBeanFactoryPostProcessors())源码
public static void invokeBeanFactoryPostProcessors(
        ConfigurableListableBeanFactory beanFactory, List<BeanFactoryPostProcessor> beanFactoryPostProcessors) {

    // Invoke BeanDefinitionRegistryPostProcessors first, if any.
    Set<String> processedBeans = new HashSet<>();

    if (beanFactory instanceof BeanDefinitionRegistry) {
        BeanDefinitionRegistry registry = (BeanDefinitionRegistry) beanFactory;
        List<BeanFactoryPostProcessor> regularPostProcessors = new ArrayList<>();
        List<BeanDefinitionRegistryPostProcessor> registryProcessors = new ArrayList<>();

        //beanFactoryPostProcessors是传进来里的对象,把传入的对象分类放入 BeanFactoryPostProcessor 和  BeanDefinitionRegistryPostProcessor
        //BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor ,是一个特殊的 BeanFactoryPostProcessor
        for (BeanFactoryPostProcessor postProcessor : beanFactoryPostProcessors) {
            if (postProcessor instanceof BeanDefinitionRegistryPostProcessor) {
                BeanDefinitionRegistryPostProcessor registryProcessor =
                        (BeanDefinitionRegistryPostProcessor) postProcessor;
                //如果传入的beanFactoryPostProcessors是它的子类,即:BeanDefinitionRegistryPostProcessor
                //则执行传入的BeanDefinitionRegistryPostProcessor的postProcessBeanDefinitionRegistry方法
                registryProcessor.postProcessBeanDefinitionRegistry(registry);
                registryProcessors.add(registryProcessor);
            } else {
                regularPostProcessors.add(postProcessor);
            }
        }

        // Do noitialize 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<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors = new ArrayList<>();

        // First, invoke the BeanDefinitionRegistryPostProcessors that implement PriorityOrdered.

        //这里只能拿到spring内部的BeanDefinitionRegistryPostProcessor,
        //因为到这里spring还没有去扫描Bean,获取不到我们通过@Component标识的自定义BeanDefinitionRegistryPostProcessor
        //一般默认情况下,这里只有一个,BeanName:org.springframework.context.annotation.internalConfigurationAnnotationProcessor
        //对应的BeanClass:ConfigurationClassPostProcessor
        String[] postProcessorNames =
                beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            if (beanFactory.isTypeMatch(ppName, PriorityOrdered.class)) {
                //beanFactory.getBean, 这里开始创建BeanDefinitionRegistryPostProcessor bean 了
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }

        //排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);

        // registryProcessors 中放的是 BeanDefinitionRegistryPostProcessor
        // 因为这里只执行eanDefinitionRegistryPostProcessor中独有的方法,而不会执行其父类即BeanFactoryProcessor的方法
        // 所以这里需要把处理器放入一个集合中,后续统一执行父类的方法
        registryProcessors.addAll(currentRegistryProcessors);

        // 执行BeanDefinitionRegistryPostProcessor,currentRegistryProcessors中放的是spring内部的BeanDefinitionRegistryPostProcessor
        // 默认情况下,只有 org.springframework.context.annotation.ConfigurationClassPostProcessor
        // ConfigurationClassPostProcessor 里面就是在执行扫描Bean,并且注册BeanDefinition
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);

        // 清空这个临时变量,方便后面再使用
        currentRegistryProcessors.clear();

        // Next, invoke the BeanDefinitionRegistryPostProcessors that implement Ordered.
        // 这里已经可以获取到我们通过注册到Spring容器的 BeanDefinitionRegistryPostProcessor 了
        postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);
        for (String ppName : postProcessorNames) {
            // 之前优先处理的是实现PriorityOrdered接口的,而PriorityOrdered接口也实现了Ordered接口
            // 所有这里需要把之前已经处理过的给过滤掉
            if (!processedBeans.contains(ppName) && beanFactory.isTypeMatch(ppName, Ordered.class)) {
                //之前这个临时变量已经被清空了,现在又开始放东西了
                currentRegistryProcessors.add(beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class));
                processedBeans.add(ppName);
            }
        }

        //排序
        sortPostProcessors(currentRegistryProcessors, beanFactory);

        registryProcessors.addAll(currentRegistryProcessors);

        // 执行BeanDefinitionRegistryPostProcessor
        invokeBeanDefinitionRegistryPostProcessors(currentRegistryProcessors, registry);

        //清空临时变量
        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) {
                //执行没有实现Ordered接口的BeanDefinitionRegistryPostProcessor
                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.
        // List<BeanDefinitionRegistryPostProcessor> registryProcessors
        // 之前已经执行过BeanDefinitionRegistryPostProcessor独有方法,现在执行其父类方法
        invokeBeanFactoryPostProcessors(registryProcessors, beanFactory);

        // List<BeanFactoryPostProcessor> regularPostProcessors
        // 执行 BeanFactoryPostProcessor 方法
        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 BeanFactoryPostProcessor 的 beanName
    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) {
        // 如果已经被执行过了,就不在执行
        // 因为一开始先获取的BeanDefinitionRegistryPostProcessor,而BeanDefinitionRegistryPostProcessor继承了BeanFactoryPostProcessor
        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.
    // 根据不同的优先级,按序执行 BeanFactoryPostProcessor
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    invokeBeanFactoryPostProcessors(priorityOrderedPostProcessors, beanFactory);

    // Next, invoke the BeanFactoryPostProcessors that implement Ordered.
    List<BeanFactoryPostProcessor> 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.
    List<BeanFactoryPostProcessor> 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();
}

源码超级长,我们慢慢来看。

  1. Spring容器使用的BeanFactoryDefaultListableBeanFactory,它实现了BeanDefinitionRegistry接口,if条件成立。

  2. 优先处理程序传进来的beanFactoryPostProcessors,也就是我们手动调用AbstractApplicationContext#addBeanFactoryPostProcessor方法来添加的BeanFactoryPostProcessor

  3. BeanFactoryPostProcessor是一个顶级接口,他还有一个子类BeanDefinitionRegistryPostProcessor。在该方法中声明了两个List来存放BeanFactoryPostProcessorBeanDefinitionRegistryPostProcessor,以便控制这两个接口方法的执行。

  4. 遍历传入的List<BeanFactoryPostProcessor> beanFactoryPostProcessors,将其分类放到两个List中。如果传入的是BeanDefinitionRegistryPostProcessor类,则先执行BeanDefinitionRegistryPostProcessor类中独有的方法postProcessBeanDefinitionRegistry方法。当然,我们这里传入的List<BeanFactoryPostProcessor> beanFactoryPostProcessors为空。

  5. 第一次执行beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);方法,从容器中获取BeanDefinitionRegistryPostProcessor类型的Bean的name(这里只是获取名称,还没有实例化Bean)。注意,程序执行到这里,Spring还没有扫描包,还没有将项目中的Bean注册到容器中。默认情况下,这里返回的数据为如下图所示。回忆一下,这个BeanDefinition是在什么时候被加入到BeanFactory的呢?是在AnnotationConfigApplicationContext的无参构造器中创建reader时注册的BeanDefinition。其中BeanName为org.springframework.context.annotation.internalConfigurationAnnotationProcessor,对应的Class为org.springframework.context.annotation.ConfigurationClassPostProcessorimage.png

  6. 遍历这个获取的postProcessorNames,如果实现了PriorityOrdered接口,就调用beanFactory.getBean(ppName, BeanDefinitionRegistryPostProcessor.class)方法,从容器中获取这个Bean,将其加入到临时变量List<BeanDefinitionRegistryPostProcessor> currentRegistryProcessors中。

  7. currentRegistryProcessors中的元素进行排序,然后执行BeanDefinitionRegistryPostProcessor中的特有方法postProcessBeanDefinitionRegistry。注意哦,这里没有执行其父类的方法,而是又将其放到List<BeanDefinitionRegistryPostProcessor> registryProcessors中,到后面再执行其父类方法。

  8. 默认情况下,此时currentRegistryProcessors中只有一个Bean即:org.springframework.context.annotation.ConfigurationClassPostProcessor(它实现了PriorityOrdered接口)。ConfigurationClassPostProcessor是一个非常重要的类,我们后面在讲。当程序执行完ConfigurationClassPostProcessorBeanDefinitionRegistryPostProcessor方法后,我们程序中的Bean就被注册到了Spring容器中了,需要注意的是,这里还只是注册了BeanDefinition,还没有创建Bean对象。currentRegistryProcessors

    ((DefaultListableBeanFactory) registry).beanDefinitionMap

  9. 当第二次执行postProcessorNames = beanFactory.getBeanNamesForType(BeanDefinitionRegistryPostProcessor.class, true, false);方法,此时因为之前已经完成了Bean的扫描,所以如果我们有自定义的BeanDefinitionRegistryPostProcessor就可以在这里被获取了。获取之前,判断其是否实现Ordered接口,并且之前没有被执行过,则调用getBean方法,从容器中获取该Bean,然后进行排序,执行postProcessBeanDefinitionRegistry方法。

  10. 前面已经按顺序执行了实现PriorityOrderedOrdered接口的BeanDefinitionRegistryPostProcessor,最后,执行没有实现Ordered接口的BeanDefinitionRegistryPostProcessorpostProcessBeanDefinitionRegistry方法。执行完之后再BeanDefinitionRegistryPostProcessor的父类方法postProcessBeanFactory

  11. 获取容器中还没有被执行过的实现BeanFactoryPostProcessor接口的Bean,然后按顺序执行的postProcessBeanFactory。默认情况下,这里会获取到:

postProcessorNames

由于Bean org.springframework.context.annotation.internalConfigurationAnnotationProcessor(对应的Class为org.springframework.context.annotation.ConfigurationClassPostProcessor)在之前已经被执行了,这里只会执行Bean org.springframework.context.event.internalEventListenerProcessor(对应的Class为org.springframework.context.event.EventListenerMethodProcessor)的postProcessBeanFactory方法,源码如下:

//org.springframework.context.event.EventListenerMethodProcessor#postProcessBeanFactory 源码
@Override
public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
    this.beanFactory = beanFactory;

    Map<String, EventListenerFactory> beans = beanFactory.getBeansOfType(EventListenerFactory.class, false, false);
    List<EventListenerFactory> factories = new ArrayList<>(beans.values());
    AnnotationAwareOrderComparator.sort(factories);
    this.eventListenerFactories = factories;
}

未完待续......

源码学习笔记:https://github.com/shenjianeng/spring-code-study

欢迎关注公众号:

Coder小黑


原文链接:https://www.cnblogs.com/coderxiaohei/p/11645764.html
如有疑问请与原作者联系

标签:

版权申明:本站文章部分自网络,如有侵权,请联系:west999com@outlook.com
特别注意:本站所有转载文章言论不代表本站观点,本站所提供的摄影照片,插画,设计作品,如需使用,请与原作者联系,版权归原作者所有

上一篇:JAVA的List接口的remove重载方法调用原理

下一篇:Spring5源码解析3-refresh方法初探