AbstractApplicationContext类refresh()方法中的第四个调用方法postProcessBeanFactory(beanFactory)，允许容器的子类去注册postProcessor ，钩子方法。
postProcessBeanFactory方法的接口声明在AbstractApplicationContext类中：
/**
* 在标准初始化后修改应用程序上下文的内部bean工厂。
* 所有bean定义都将被加载，但是没有bean会被实例化。
* 这允许在某些应用上下文实现中注册特殊的BeanPostProcessors等。
*
* 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.
* @param beanFactory the bean factory used by the application context 应用环境下的Bean工厂
*/
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
}
postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory)
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);
}
addBeanPostProcessor
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));
/**
* 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
* @param beanPostProcessor the post-processor to register
*/
@Override
public void addBeanPostProcessor(BeanPostProcessor beanPostProcessor) {
Assert.notNull(beanPostProcessor, "BeanPostProcessor must not be null");
// Remove from old position, if any
//beanPostProcessors是一个ArrayList，持有在创建bean时被应用的BeanPostProcessors
this.beanPostProcessors.remove(beanPostProcessor);
// Track whether it is instantiation/destruction aware
//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;
}
// Add to end of list
this.beanPostProcessors.add(beanPostProcessor);
}
registerWebApplicationScopes
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
* @param beanFactory the BeanFactory to configure
* @param sc the ServletContext that we're running within
*/
public static void registerWebApplicationScopes(ConfigurableListableBeanFactory beanFactory,
@Nullable 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());
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);
}
}
registerScope
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.isDebugEnabled()) {
logger.debug("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.isTraceEnabled()) {
logger.trace("Registering scope '" + scopeName + "' with implementation [" + scope + "]");
}
}
}
registerEnvironmentBeans
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
* @param bf the BeanFactory to configure
* @param servletContext the ServletContext that we're running within
* @param servletConfig the ServletConfig
*/
public static void registerEnvironmentBeans(ConfigurableListableBeanFactory bf,
@Nullable ServletContext servletContext, @Nullable 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<>();
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<>();
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));
}
}
registerSingleton
此方法的实现在DefaultListableBeanFactory类中
//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);
public class DefaultListableBeanFactory extends AbstractAutowireCapableBeanFactory
implements ConfigurableListableBeanFactory, BeanDefinitionRegistry, Serializable {
@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);
// 仍然处于启动注册阶段
//属于手动注册情况
updateManualSingletonNames(set -> set.add(beanName), set -> !this.beanDefinitionMap.containsKey(beanName));
//删除按照类型映射有关的任何假设
clearByTypeCache();
}
private void updateManualSingletonNames(Consumer<Set<String>> action, Predicate<Set<String>> condition) {
//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 (condition.test(this.manualSingletonNames)) {
Set<String> updatedSingletons = new LinkedHashSet<>(this.manualSingletonNames);
action.accept(updatedSingletons);
this.manualSingletonNames = updatedSingletons;
}
}
}
else {
// Still in startup registration phase
if (condition.test(this.manualSingletonNames)) {
action.accept(this.manualSingletonNames);
}
}
}
/**
* 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();
}
}
registerSingleton
此方法的实现在DefaultSingletonBeanRegistry类中
//3.1.1调用父类方法，注册单例
super.registerSingleton(beanName, singletonObject);
public class DefaultSingletonBeanRegistry extends SimpleAliasRegistry implements SingletonBeanRegistry {
/** Cache of singleton objects: bean name to bean instance. */
private final Map<String, Object> singletonObjects = new ConcurrentHashMap<>(256);
/** Cache of singleton factories: bean name to ObjectFactory. */
private final Map<String, ObjectFactory<?>> singletonFactories = new HashMap<>(16);
/** Cache of early singleton objects: bean name to bean instance. */
private final Map<String, Object> earlySingletonObjects = new HashMap<>(16);
/** Set of registered singletons, containing the bean names in registration order. */
private final Set<String> registeredSingletons = new LinkedHashSet<>(256);
/**
* 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
* @param beanName the name of the bean
* @param singletonObject the existing singleton object
* @throws IllegalStateException
*/
@Override
public void registerSingleton(String beanName, Object singletonObject) throws IllegalStateException {
Assert.notNull(beanName, "Bean name must not be null");
Assert.notNull(singletonObject, "Singleton object 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
* @param beanName the name of the bean
* @param singletonObject the singleton object
*/
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);
//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);
}
}
}
这样AbstractRefreshableWebApplicationContext中的postProcessBeanFactory方法就分析完了
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