postProcessBeanFactory方法源码跟踪

看这篇文章之前可以先了解之前的跟踪流程，https://www.jianshu.com/p/4934233f0ead

代码过宽，可以shift + 鼠标滚轮 左右滑动查看

AbstractApplicationContext类refresh()方法中的第四个调用方法postProcessBeanFactory()的跟踪。

@Override
public void refresh() throws BeansException, IllegalStateException {
    synchronized (this.startupShutdownMonitor) {
        ...
        try {
            // Allows post-processing of the bean factory in context subclasses.
            // 允许在上下文的子类中对bean factory进行后处理
            postProcessBeanFactory(beanFactory);
        ···
 }

断点进入跟踪。

postProcessBeanFactory(零)

此方法的实现在AbstractRefreshableWebApplicationContext类中，它是XmlWebApplicationContext的父类。进入方法查看：

/**
* Register request/session scopes, a {@link ServletContextAwareProcessor}, etc.
*
* 注册request/session scopes，一个ServletContextAwareProcessor处理器等。
*/
@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {

    //ServletContextAwareProcessor中拿到应用上下文持有的servletContext引用和servletConfig引用
    //1.添加ServletContextAwareProcessor处理器
    beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));

    //在自动注入时忽略指定的依赖接口
    //通常被应用上下文用来注册以其他方式解析的依赖项
    beanFactory.ignoreDependencyInterface(ServletContextAware.class);
    beanFactory.ignoreDependencyInterface(ServletConfigAware.class);

    //2.注册web应用的scopes
    WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);

    //3.注册和环境有关的beans
    WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}

postProcessBeanFactory方法的接口声明在AbstractApplicationContext类中：

/**
* Modify the application context's internal bean factory after its standard
* initialization. All bean definitions will have been loaded, but no beans
* will have been instantiated yet. This allows for registering special
* BeanPostProcessors etc in certain ApplicationContext implementations.
*
* 在应用上下文的内部bean factory初始化之后修改bean factory。
* 所有的bean definitions已经被加载，但是还没有bean被实例化。
* 在明确的ApplicationContext实现中允许指定BeanPostProcessors等的注册
*/
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}

1.addBeanPostProcessor

跟踪标记为1的方法

此方法的实现在AbstractBeanFactory类中

这里要注册的处理器ServletContextAwareProcessor带有Aware单词，这个单词是“有意识、能意识到”的意思，个人理解就是能意识到ServletContext的存在，也就是能拿到ServletContext的引用，或者能对其进行设置。

//1.添加ServletContextAwareProcessor处理器
beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));

/**
* Add a new BeanPostProcessor that will get applied to beans created
* by this factory. To be invoked during factory configuration.
* <p>Note: Post-processors submitted here will be applied in the order of
* registration; any ordering semantics expressed through implementing the
* {@link org.springframework.core.Ordered} interface will be ignored. Note
* that autodetected post-processors(e.g. as beans in an ApplicationContext)
* will always be applied after programmatically registered ones.
*
* 添加一个新的BeanPostProcessor，在工厂创建bean的时候会应用得到。
* 在工厂配置时被调用。
* 注意：Post-processors是按照注册的顺序被提交的
* 任何通过实现Ordered接口的排序表达式都将被忽略。
* 注意，自动检测的post-processors（作为一个在ApplicationContext的bean）总是在编程方式注册后才会被使用。
*/
@Override
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {

    Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");

    //beanPostProcessors是一个ArrayList，持有在创建bean时被应用的BeanPostProcessors
    this.beanPostProcessors.remove(beanPostProcessor);
    this.beanPostProcessors.add(beanPostProcessor);

    //InstantiationAwareBeanPostProcessor这个接口有两个方法
    //一个在实例化之前被调用
    //一个在实例化之后，初始化之前被调用，可以用来做一些特殊用途，比如代理
    if (beanPostProcessor instanceof InstantiationAwareBeanPostProcessor) {
        this.hasInstantiationAwareBeanPostProcessors = true;
    }

    //DestructionAwareBeanPostProcessor这个接口只有一个方法，在被销毁前调用
    if (beanPostProcessor instanceof DestructionAwareBeanPostProcessor) {
        this.hasDestructionAwareBeanPostProcessors = true;
    }
}

2.registerWebApplicationScopes

跟踪标记为2的方法

此方法的实现在WebApplicationContextUtils类中

//2.注册web应用的scopes
WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);

/**
* Register web-specific scopes ("request", "session", "globalSession", "application")
* with the given BeanFactory, as used by the WebApplicationContext.
*
* 注册web特有的scopes("request", "session", "globalSession", "application")到指定的bean工厂
* 被WebApplicationContext使用
*/
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory, ServletContext sc) {

    //2.1注册request Scope
    beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());

    //注册session Scope
    beanFactory.registerScope(WebApplicationContext.SCOPE_SESSION, new SessionScope(false));

    //注册global session Scope
    beanFactory.registerScope(WebApplicationContext.SCOPE_GLOBAL_SESSION, new SessionScope(true));
    if (sc != null) {
        ServletContextScope appScope = new ServletContextScope(sc);

        //注册application Scope
        beanFactory.registerScope(WebApplicationContext.SCOPE_APPLICATION, appScope);

        // Register as ServletContext attribute, for ContextCleanupListener to detect it.
        // 为了能让ContextCleanupListener监听器检测到，
        // 将application Scope作为ServletContext的属性进行注册
        sc.setAttribute(ServletContextScope.class.getName(), appScope);
    }

    //ServletRequest.class为key，对象为value放入到了beanFactory的resolvableDependencies属性中
    //resolvableDependencies是一个ConcurrentHashMap，映射依赖类型和对应的被注入的value
    //value要是依赖类型的实例，要不value就应该是个ObjectFactory
    //ObjectFactory和FactoryBean的区别可以看下文参考
    beanFactory.registerResolvableDependency(ServletRequest.class, new RequestObjectFactory());
    beanFactory.registerResolvableDependency(ServletResponse.class, new ResponseObjectFactory());
    beanFactory.registerResolvableDependency(HttpSession.class, new SessionObjectFactory());
    beanFactory.registerResolvableDependency(WebRequest.class, new WebRequestObjectFactory());

    //是否存在jsf
    if (jsfPresent) {
        FacesDependencyRegistrar.registerFacesDependencies(beanFactory);
    }
}

2.1 registerScope

跟踪标记为2.1的方法

此方法的实现在AbstractBeanFactory类中

//2.1注册request Scope
beanFactory.registerScope(WebApplicationContext.SCOPE_REQUEST, new RequestScope());

@Override
public void registerScope(String scopeName, Scope scope) {

    Assert.notNull(scopeName, "Scope identifier must not be null");
    Assert.notNull(scope, "Scope must not be null");

    //singleton和prototype在这个方法中不进行注册
    if (SCOPE_SINGLETON.equals(scopeName) || SCOPE_PROTOTYPE.equals(scopeName)) {

        //不能替换已存在的 singleton scope和 prototype scope
        throw new IllegalArgumentException("Cannot replace existing scopes 'singleton' and 'prototype'");
    }

    //scopes是AbstractBeanFactory的LinkedHashMap属性
    Scope previous = this.scopes.put(scopeName, scope);

    //打印日志
    if (previous != null && previous != scope) {

        //对已经注册过的scope进行替换
        if (logger.isInfoEnabled()) {
            logger.info("Replacing scope '" + scopeName + "' from [" + previous + "] to [" + scope + "]");
        }
    }
    else {

        //没注册过的和同一个实例注册两次的scope都打印日志记录下
        if (logger.isDebugEnabled()) {
            logger.debug("Registering scope '" + scopeName + "' with implementation [" + scope + "]");
        }
    }
}

3.registerEnvironmentBeans

跟踪标记为3的方法

此方法的实现在WebApplicationContextUtils类中

//3.注册和环境有关的beans
WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);

/**
* Register web-specific environment beans ("contextParameters", "contextAttributes")
* with the given BeanFactory, as used by the WebApplicationContext.
*
* 注册web特有的environment beans ("contextParameters", "contextAttributes")到指定工厂中
* 被WebApplicationContext所使用
*/
public static void registerEnvironmentBeans(
    ConfigurableListableBeanFactory bf, ServletContext servletContext, ServletConfig servletConfig) {

    //单例或者beanDefinition中不包含servletContext进入条件
    if (servletContext != null && !bf.containsBean(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME)) {

        //3.1注册servletContext单例，注册方法跟踪过一次，这里再跟踪一次加深印象
        bf.registerSingleton(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME, servletContext);
    }

    //单例或者beanDefinition中不包含servletConfig进入条件
    if (servletConfig != null && !bf.containsBean(ConfigurableWebApplicationContext.SERVLET_CONFIG_BEAN_NAME)) {

        //注册servletConfig单例
        bf.registerSingleton(ConfigurableWebApplicationContext.SERVLET_CONFIG_BEAN_NAME, servletConfig);
    }

    //单例或者beanDefinition中不包含contextParameters进入条件
    if (!bf.containsBean(WebApplicationContext.CONTEXT_PARAMETERS_BEAN_NAME)) {
        Map<String, String> parameterMap = new HashMap<String, String>();
        if (servletContext != null) {
            Enumeration<?> paramNameEnum = servletContext.getInitParameterNames();
            while (paramNameEnum.hasMoreElements()) {
                String paramName = (String) paramNameEnum.nextElement();

                //将servletContext参数配置放入集合中
                //也就是web.xml中context-param标签里的param-name和param-value
                parameterMap.put(paramName, servletContext.getInitParameter(paramName));
            }
        }
        if (servletConfig != null) {
            Enumeration<?> paramNameEnum = servletConfig.getInitParameterNames();
            while (paramNameEnum.hasMoreElements()) {
                String paramName = (String) paramNameEnum.nextElement();

                //将servletConfig中的参数配置放入集合
                parameterMap.put(paramName, servletConfig.getInitParameter(paramName));
            }
        }

        //以contextParameters作为name，集合转换成不可修改状态，作为value，进行注册
        bf.registerSingleton(WebApplicationContext.CONTEXT_PARAMETERS_BEAN_NAME,
                             Collections.unmodifiableMap(parameterMap));
    }

	//单例或者beanDefinition中不包含contextAttributes进入条件
    if (!bf.containsBean(WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME)) {
        Map<String, Object> attributeMap = new HashMap<String, Object>();
        if (servletContext != null) {
            Enumeration<?> attrNameEnum = servletContext.getAttributeNames();
            while (attrNameEnum.hasMoreElements()) {
                String attrName = (String) attrNameEnum.nextElement();

                //将servletContext中设置的Attribute放入集合
                attributeMap.put(attrName, servletContext.getAttribute(attrName));
            }
        }

        //以contextAttributes作为name，集合转换成不可修改状态，作为value，进行注册
        bf.registerSingleton(WebApplicationContext.CONTEXT_ATTRIBUTES_BEAN_NAME,
                             Collections.unmodifiableMap(attributeMap));
    }
}

3.1 registerSingleton

跟踪标记为3.1的方法

此方法的实现在DefaultListableBeanFactory类中

//3.1注册servletContext单例
bf.registerSingleton(WebApplicationContext.SERVLET_CONTEXT_BEAN_NAME, servletContext);

@Override
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {

    //3.1.1调用父类方法，注册单例
    super.registerSingleton(beanName, singletonObject);

    //AbstractBeanFactory类中有个集合属性alreadyCreated
    //里面保存在至少被创建过一次的beanName
    //如果这个集合中存在beanName，那么说明已经进入了bean创建阶段
    if (hasBeanCreationStarted()) {

        // Cannot modify startup-time collection elements anymore (for stable iteration)
        // 无法再修改启动时集合元素（为了稳定迭代）
        synchronized (this.beanDefinitionMap) {

            //beanName不在beanDefinitionMap中，说明是手动注册
            if (!this.beanDefinitionMap.containsKey(beanName)) {
                Set<String> updatedSingletons = new LinkedHashSet<String>(this.manualSingletonNames.size() + 1);
                updatedSingletons.addAll(this.manualSingletonNames);
                updatedSingletons.add(beanName);
                this.manualSingletonNames = updatedSingletons;
            }
        }
    }
    else {

        // Still in startup registration phase
        // 仍然处于启动注册阶段
        if (!this.beanDefinitionMap.containsKey(beanName)) {

            //属于手动注册情况
            this.manualSingletonNames.add(beanName);
        }
    }

    //进入这个方法查看
    clearByTypeCache();
}

/**
* Remove any assumptions about by-type mappings.
*
* 删除按照类型映射有关的任何假设
*/
private void clearByTypeCache() {

    //allBeanNamesByType是单例和非单例beanName的映射，key是依赖类型
    this.allBeanNamesByType.clear();

    //仅单例beanName的映射，key是依赖类型
    this.singletonBeanNamesByType.clear();
}

3.1.1 registerSingleton

跟踪标记为3.1.1的方法

此方法的实现在DefaultSingletonBeanRegistry类中

//2.1调用父类方法，注册单例
super.registerSingleton(beanName, singletonObject);

/**
* Register the given existing object as singleton in the bean registry,
* under the given bean name.
* <p>The given instance is supposed to be fully initialized; the registry
* will not perform any initialization callbacks (in particular, it won't
* call InitializingBean's {@code afterPropertiesSet} method).
* The given instance will not receive any destruction callbacks
* (like DisposableBean's {@code destroy} method) either.
* <p>When running within a full BeanFactory: <b>Register a bean definition
* instead of an existing instance if your bean is supposed to receive
* initialization and/or destruction callbacks.</b>
* <p>Typically invoked during registry configuration, but can also be used
* for runtime registration of singletons. As a consequence, a registry
* implementation should synchronize singleton access; it will have to do
* this anyway if it supports a BeanFactory's lazy initialization of singletons.
*
* 在给定的bean name下，将存在的对象作为单例注册在工厂中
* 给定的实例应该是完全初始化；工厂不执行任何初始化回调（特别是，他不会调用InitializingBean的
* afterPropertiesSet方法）
* 给定的实例也不接收任何销毁回调（像DisposableBean的destroy方法）
* 当在完整的BeanFactory运行时：
* 如果你的bean需要接收初始化或者销毁的回调，注册一个bean definition替代一个存在的实例
* 通常此方法在工厂配置时被调用，也能在运行时单例注册时被调用。
* 作为结果，工厂的实现应该同步单例的访问；如果支持BeanFactory的单例的延迟初始化就不得不这样做
*/
@Override
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
    Assert.notNull(beanName, "'beanName' must not be null");
    synchronized (this.singletonObjects) {
        Object oldObject = this.singletonObjects.get(beanName);

        //不能注册两次
        if (oldObject != null) {
            throw new IllegalStateException("Could not register object [" + singletonObject +
                                            "] under bean name '" + beanName + "': there is already object [" + oldObject + "] bound");
        }

        //进入这个方法
        addSingleton(beanName, singletonObject);
    }
}

/**
* Add the given singleton object to the singleton cache of this factory.
* <p>To be called for eager registration of singletons.
*
* 添加给定单例对象到工厂的单例缓存中
* 用来被提早注册的单例调用
*/
protected void addSingleton(String beanName, Object singletonObject) {
    synchronized (this.singletonObjects) {

        //singletonObjects是一个ConcurrentHashMap
        //用来缓存单例对象
        this.singletonObjects.put(beanName, (singletonObject != null ? singletonObject : NULL_OBJECT));

        //singletonFactories是一个HashMap
        //里面缓存着单例工厂
        this.singletonFactories.remove(beanName);

        //早期单例对象
        //earlySingletonObjects是一个HashMap
        this.earlySingletonObjects.remove(beanName);

        //registeredSingletons是一个LinkedHashSet
        //被注册单例的集合，以注册的顺序包含着bean name
        this.registeredSingletons.add(beanName);
    }
}

postProcessBeanFactory方法也跟踪完了。

未完···

参考

FactoryBean与ObjectFactory区别:

https://blog.csdn.net/m0_38043362/article/details/80284577

总结

• 添加后处理器、忽略依赖接口
• 2.注册web应用的scopes
• 3.注册和环境有关的beans

——————————————————————————————————

• 2
• 在工厂中注册request session globalSession Scope
• 如果 ServletContext 不为null，用Scope实现类包裹后注册到工厂，注册为application。同时在ServletContext 的属性中保存一份。
• 在工厂中注册各种可解析依赖

——————————————————————————————————

• 3
• 当 servletContext 不为null时，工厂以及其父工厂中没有对应单例或者BeanDefinition，那么就在工厂中注册单例，并标记为手动注册的单例
• 同上注册 servletConfig
• 拿到 servletContext 和 servletConfig 中的初始参数，都放入到map中，然后注册到工厂，name为 contextParameters ，最后标记为手动注册
• 拿到 servletContext 中的属性，都放入到map中，然后注册到工厂，name为 contextAttributes，最后标记为手动注册