Spring上下文刷新第六步

这个方法和第五步的方法相似,对BeanPostProcess按照排序优先级加入BeanFactory中,但是少了执行(invok)的步骤,用以Bean创建过程中调用(可参考我Bean生命周期那个文章).其中注入的MergedBeanDefinitionPostProcessor涉及到Bean生命周期和IOC功能可以结合流程分明的Spring的Bean生命周期、Spring控制反转IOC和依赖注入DI结构化简述看一下

public static void registerBeanPostProcessors(
        ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {

    String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);

    int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
    // 加了一个自定义的BeanPostProcessor.大概意思是检测BeanPostProcessor是否符合规范
    beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));

    // 创建不同优先级BeanPostProcessor容器,在for循环中进行分类
    List<BeanPostProcessor> priorityOrderedPostProcessors = new ArrayList<>();
    List<BeanPostProcessor> internalPostProcessors = new ArrayList<>();
    List<String> orderedPostProcessorNames = new ArrayList<>();
    List<String> 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);
        }
    }

    // 注册加入高优先级BeanPostProcessor
    sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);

    // 注册加入中优先级BeanPostProcessor
    List<BeanPostProcessor> 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);

    // 注册加入常规BeanPostProcessor
    List<BeanPostProcessor> 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);

    // 上面将所有的internal BeanPostProcessors筛选出来统一放到最低优先级加入
    sortPostProcessors(internalPostProcessors, beanFactory);
    registerBeanPostProcessors(beanFactory, internalPostProcessors);

    // 注册检查BeanPostProcessor是否是ApplicationListener并加入上下文的Listener容器中
    beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}

registerBeanPostProcessors注册方法

注册加入方法

private static void registerBeanPostProcessors(
        ConfigurableListableBeanFactory beanFactory, List<BeanPostProcessor> postProcessors) {

    if (beanFactory instanceof AbstractBeanFactory) {
        // Bulk addition is more efficient against our CopyOnWriteArrayList there
        ((AbstractBeanFactory) beanFactory).addBeanPostProcessors(postProcessors);
    }
    else {
        for (BeanPostProcessor postProcessor : postProcessors) {
            beanFactory.addBeanPostProcessor(postProcessor);
        }
    }
}

MergedBeanDefinitionPostProcessor接口

该接口涉及到Bean生命周期***能.在AbstractAutowireCapableBeanFactory类的doGreateBean中有调用使用,主要是两个对Bean内部属性注解扫描类,用于在Bean实例化后给Bean属性赋值.

在将MergedBeanDefinitionPostProcessor加入BeanFactory中后,创建Bean时对Bean的类属性信息解析,并将解析内容添加到了BeanDefinition上(在AbstractAutowireCapableBeanFactory类的576行).

解析执行代码

AutowiredAnnotationBeanPostProcessor负责查找解析@Autowire和@Value标注的属性添加到BeanDefinition中

public AutowiredAnnotationBeanPostProcessor() {
    this.autowiredAnnotationTypes.add(Autowired.class);
    this.autowiredAnnotationTypes.add(Value.class);
}

public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
    InjectionMetadata metadata = findAutowiringMetadata(beanName, beanType, null);
    metadata.checkConfigMembers(beanDefinition);
}

CommonAnnotationBeanPostProcessor负责解析@Resource和@PostConstruct、@PreDestroy注解(继承了InitDestroyAnnotationBeanPostProcessor).并将标注的属性和初始化、销毁方法加入BeanDefinition中

static {
    webServiceRefClass = loadAnnotationType("javax.xml.ws.WebServiceRef");
    ejbClass = loadAnnotationType("javax.ejb.EJB");

    resourceAnnotationTypes.add(Resource.class);
    if (webServiceRefClass != null) {
        resourceAnnotationTypes.add(webServiceRefClass);
    }
    if (ejbClass != null) {
        resourceAnnotationTypes.add(ejbClass);
    }
}

public CommonAnnotationBeanPostProcessor() {
    setOrder(Ordered.LOWEST_PRECEDENCE - 3);
    setInitAnnotationType(PostConstruct.class);
    setDestroyAnnotationType(PreDestroy.class);
    ignoreResourceType("javax.xml.ws.WebServiceContext");
}
// 先执行父类的查找注解方法,再查找@Resource注解标注的属性信息加入BeanDefinition中
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
    super.postProcessMergedBeanDefinition(beanDefinition, beanType, beanName);
    InjectionMetadata metadata = findResourceMetadata(beanName, beanType, null);
    metadata.checkConfigMembers(beanDefinition);
}
// 查找Bean生命周期涉及到初始化和销毁方法注解.添加到BeanDefinition中
public void postProcessMergedBeanDefinition(RootBeanDefinition beanDefinition, Class<?> beanType, String beanName) {
    LifecycleMetadata metadata = findLifecycleMetadata(beanType);
    metadata.checkConfigMembers(beanDefinition);
}

扫描信息使用

这些被扫描到BeanDefinition中后在AbstractAutowireCapableBeanFactory类的601行读取BeanDefinition添加对应的Bean依赖进去

参考

MergedBeanDefinitionPostProcessor和@Autowired，@Value的关系
 Spring中@Value注解有多强大