版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/J080624/article/details/83444209
该篇博文是基于xml配置，非SpringBoot项目。
一般项目中使用Tomcat作为Web容器时会有三个容器，ServletContext-Tomcat启动时创建，然后会分别再创建Spring容器-Root WebApplicationContext-IOC容器和SpringMVC容器。
Spring容器以属性(org.springframework.web.context.WebApplicationContext.ROOT)-值(Root WebApplicationContext)放置在ServletContext中，SpringMVC容器以属性(org.springframework.web.servlet.FrameworkServlet.CONTEXT.springMVC)-值(WebApplicationContext)放置在ServletContext容器中。
同时，Spring容器是SpringMVC容器的父容器！
【1】Spring容器的创建
Tomcat启动会检测classpath是否有WebApplicationInitializer，然后创建ServletContext之后读取web.xml中节点。其中ContextLoaderListener会创建Spring root WebApplicationContext。
① ContextLoaderListener.contextInitialized()方法
/**
* Initialize the root web application context.
*/
@Override
public void contextInitialized(ServletContextEvent event) {
//参考②
initWebApplicationContext(event.getServletContext());
}
② ContextLoader.initWebApplicationContext()方法源码如下：
// 这里ServletContext为org.apache.catalina.core.ApplicationContextFacade@7824f26a
//ApplicationContextFacade：从Web应用程序中屏蔽内部应用程序上下文对象的外观对象
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
throw new IllegalStateException(
"Cannot initialize context because there is already a root application context present - " +
"check whether you have multiple ContextLoader* definitions in your web.xml!");
}
Log logger = LogFactory.getLog(ContextLoader.class);
servletContext.log("Initializing Spring root WebApplicationContext");
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
long startTime = System.currentTimeMillis();
try {
// Store context in local instance variable, to guarantee that
// it is available on ServletContext shutdown.
if (this.context == null) {
this.context = createWebApplicationContext(servletContext);
}
if (this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent ->
// determine parent for root web application context, if any.
//给Root WebApplicationContext设置父容器，默认返回null
//通常这里你可以设想父容器为Servlet
ApplicationContext parent = loadParentContext(servletContext);
cwac.setParent(parent);
}
//配置并刷新Root WebApplicationContext 参考③
configureAndRefreshWebApplicationContext(cwac, servletContext);
}
}
//以org.springframework.web.context.WebApplicationContext.ROOT为属性，放到servletContext
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl == ContextLoader.class.getClassLoader()) {
currentContext = this.context;
}
else if (ccl != null) {
currentContextPerThread.put(ccl, this.context);
}
if (logger.isDebugEnabled()) {
logger.debug("Published root WebApplicationContext as ServletContext attribute with name [" +
WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE + "]");
}
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
logger.info("Root WebApplicationContext: initialization completed in " + elapsedTime + " ms");
}
return this.context;
}
catch (RuntimeException ex) {
logger.error("Context initialization failed", ex);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
throw ex;
}
catch (Error err) {
logger.error("Context initialization failed", err);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, err);
throw err;
}
}
这里分别说明一下WebApplicationContext和ServletContext。
ServletContext如下图所示：
你可以理解为，项目中使用到的ServletContext即为org.apache.catalina.core.ApplicationContextFacade。
那么Spring中的ApplicationContext呢？如下图所示：
③ ContextLoader.configureAndRefreshWebApplicationContext()方法
源码如下：
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
String idParam = sc.getInitParameter(CONTEXT_ID_PARAM);
if (idParam != null) {
wac.setId(idParam);
}
// id：org.springframework.web.context.WebApplicationContext:
else {
// Generate default id...
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(sc.getContextPath()));
}
}
// 设置关联的上下文ApplicationContextFacade
wac.setServletContext(sc);
//设置配置文件classpath:applicationContext.xml
String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocationParam != null) {
wac.setConfigLocation(configLocationParam);
}
//设置环境
// The wac environment's #initPropertySources will be called in any case when the context
// is refreshed; do it eagerly here to ensure servlet property sources are in place for
// use in any post-processing or initialization that occurs below prior to #refresh
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(sc, null);
}
/*
在配置位置被提供给上下文之后，但是在上下文被<em>刷新</em>之前，
自定义由ContextLoader创建的{@link ConfigurableWebApplicationContext}。
*/
//参考④
customizeContext(sc, wac);
//重要方法！参考⑤
wac.refresh();
}
④ ContextLoader.customizeContext()
遍历系统中的ApplicationContextInitializer，调用其initialize方法：
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {
List<Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> initializerClasses =
determineContextInitializerClasses(sc);
for (Class<ApplicationContextInitializer<ConfigurableApplicationContext>> initializerClass : initializerClasses) {
Class<?> initializerContextClass =
GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);
if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) {
throw new ApplicationContextException(String.format(
"Could not apply context initializer [%s] since its generic parameter [%s] " +
"is not assignable from the type of application context used by this " +
"context loader: [%s]", initializerClass.getName(), initializerContextClass.getName(),
wac.getClass().getName()));
}
this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass));
}
AnnotationAwareOrderComparator.sort(this.contextInitializers);
for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) {
initializer.initialize(wac);
}
}
⑤ AbstractApplicationContext.refresh() 方法
源码如下：
@Override
public void refresh() throws BeansException, IllegalStateException {
//同步代码块
synchronized (this.startupShutdownMonitor) {
// Prepare this context for refreshing.
prepareRefresh();
// Tell the subclass to refresh the internal bean factory.
//告诉子类去刷新内部Bean 工程，这一步会加载一些bean定义放到BeanFactory中
ConfigurableListableBeanFactory beanFactory = obtainFreshBeanFactory();
// Prepare the bean factory for use in this context.
//配置工厂的标准上下文特性，例如上下文的类加载器和后置处理器
//参考⑥
prepareBeanFactory(beanFactory);
try {
// Allows post-processing of the bean factory in context subclasses.
//bean工厂后置处理--允许创建实例后再进行修改
//参考⑦
postProcessBeanFactory(beanFactory);
// Invoke factory processors registered as beans in the context.
//初始化并按次序(如果设置了order)调用所有已注册的BeanFactoryPostProcessors
invokeBeanFactoryPostProcessors(beanFactory);
// Register bean processors that intercept bean creation.
//初始化并按次序(如果设置了order)调用所有已注册的BeanPostProcessors
//参考 ⑧
registerBeanPostProcessors(beanFactory);
// Initialize message source for this context.
//读取properties的，并支持国际化的bean
initMessageSource();
// Initialize event multicaster for this context.
//初始化程序事件广播器--单例
//尝试从BeanFactory中根据属性applicationEventMulticaster获取；
//如果没有则创建一个SimpleApplicationEventMulticaster并注册到BeanFactory
initApplicationEventMulticaster();
// Initialize other special beans in specific context subclasses.
// 在特定上下文子类中初始化其他特殊bean
//参考⑨
onRefresh();
// Check for listener beans and register them.
//参考（10）
registerListeners();
// Instantiate all remaining (non-lazy-init) singletons.
//参考 （11）
finishBeanFactoryInitialization(beanFactory);
// Last step: publish corresponding event.
//参考 （12）
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.
destroyBeans();
// Reset 'active' flag.
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();
}
}
}
⑥ AbstractApplicationContext.prepareBeanFactory()方法
注册了一些基础的、项目中很可能使用的、为其他bean提供服务的bean。源码如下：
protected void prepareBeanFactory(ConfigurableListableBeanFactory beanFactory) {
// Tell the internal bean factory to use the context's class loader etc.
beanFactory.setBeanClassLoader(getClassLoader());
beanFactory.setBeanExpressionResolver(new StandardBeanExpressionResolver(beanFactory.getBeanClassLoader()));
beanFactory.addPropertyEditorRegistrar(new ResourceEditorRegistrar(this, getEnvironment()));
// Configure the bean factory with context callbacks.
beanFactory.addBeanPostProcessor(new ApplicationContextAwareProcessor(this));
beanFactory.ignoreDependencyInterface(EnvironmentAware.class);
beanFactory.ignoreDependencyInterface(EmbeddedValueResolverAware.class);
beanFactory.ignoreDependencyInterface(ResourceLoaderAware.class);
beanFactory.ignoreDependencyInterface(ApplicationEventPublisherAware.class);
beanFactory.ignoreDependencyInterface(MessageSourceAware.class);
beanFactory.ignoreDependencyInterface(ApplicationContextAware.class);
// BeanFactory interface not registered as resolvable type in a plain factory.
// MessageSource registered (and found for autowiring) as a bean.
beanFactory.registerResolvableDependency(BeanFactory.class, beanFactory);
beanFactory.registerResolvableDependency(ResourceLoader.class, this);
beanFactory.registerResolvableDependency(ApplicationEventPublisher.class, this);
beanFactory.registerResolvableDependency(ApplicationContext.class, this);
// Register early post-processor for detecting inner beans as ApplicationListeners.
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(this));
// Detect a LoadTimeWeaver and prepare for weaving, if found.
if (beanFactory.containsBean(LOAD_TIME_WEAVER_BEAN_NAME)) {
beanFactory.addBeanPostProcessor(new LoadTimeWeaverAwareProcessor(beanFactory));
// Set a temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(new ContextTypeMatchClassLoader(beanFactory.getBeanClassLoader()));
}
// Register default environment beans.
if (!beanFactory.containsLocalBean(ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(ENVIRONMENT_BEAN_NAME, getEnvironment());
}
if (!beanFactory.containsLocalBean(SYSTEM_PROPERTIES_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_PROPERTIES_BEAN_NAME, getEnvironment().getSystemProperties());
}
if (!beanFactory.containsLocalBean(SYSTEM_ENVIRONMENT_BEAN_NAME)) {
beanFactory.registerSingleton(SYSTEM_ENVIRONMENT_BEAN_NAME, getEnvironment().getSystemEnvironment());
}
}
⑦ AbstractRefreshableWebApplicationContext.postProcessBeanFactory()方法
源码如下：
/**
* Register request/session scopes, a {@link ServletContextAwareProcessor}, etc.
*/
@Override
protected void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) {
beanFactory.addBeanPostProcessor(new ServletContextAwareProcessor(this.servletContext, this.servletConfig));
beanFactory.ignoreDependencyInterface(ServletContextAware.class);
beanFactory.ignoreDependencyInterface(ServletConfigAware.class);
WebApplicationContextUtils.registerWebApplicationScopes(beanFactory, this.servletContext);
WebApplicationContextUtils.registerEnvironmentBeans(beanFactory, this.servletContext, this.servletConfig);
}
⑧ AbstractApplicationContext.registerBeanPostProcessors()
源码如下：
/**
* Instantiate and invoke all registered BeanPostProcessor beans,
* respecting explicit order if given.
* <p>Must be called before any instantiation of application beans.
*/
protected void registerBeanPostProcessors(ConfigurableListableBeanFactory beanFactory) {
PostProcessorRegistrationDelegate.registerBeanPostProcessors(beanFactory, this);
}
其调用了PostProcessorRegistrationDelegate的registerBeanPostProcessors方法：
public static void registerBeanPostProcessors(
ConfigurableListableBeanFactory beanFactory, AbstractApplicationContext applicationContext) {
String[] postProcessorNames = beanFactory.getBeanNamesForType(BeanPostProcessor.class, true, false);
// Register BeanPostProcessorChecker that logs an info message when
// a bean is created during BeanPostProcessor instantiation, i.e. when
// a bean is not eligible for getting processed by all BeanPostProcessors.
int beanProcessorTargetCount = beanFactory.getBeanPostProcessorCount() + 1 + postProcessorNames.length;
beanFactory.addBeanPostProcessor(new BeanPostProcessorChecker(beanFactory, beanProcessorTargetCount));
// Separate between BeanPostProcessors that implement PriorityOrdered,
// Ordered, and the rest.
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);
}
}
// First, register the BeanPostProcessors that implement PriorityOrdered.
sortPostProcessors(priorityOrderedPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, priorityOrderedPostProcessors);
// Next, register the BeanPostProcessors that implement Ordered.
List<BeanPostProcessor> orderedPostProcessors = new ArrayList<>();
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);
// Now, register all regular BeanPostProcessors.
List<BeanPostProcessor> nonOrderedPostProcessors = new ArrayList<>();
for (String ppName : nonOrderedPostProcessorNames) {
BeanPostProcessor pp = beanFactory.getBean(ppName, BeanPostProcessor.class);
nonOrderedPostProcessors.add(pp);
if (pp instanceof MergedBeanDefinitionPostProcessor) {
internalPostProcessors.add(pp);
}
}
registerBeanPostProcessors(beanFactory, nonOrderedPostProcessors);
// Finally, re-register all internal BeanPostProcessors.
sortPostProcessors(internalPostProcessors, beanFactory);
registerBeanPostProcessors(beanFactory, internalPostProcessors);
// Re-register post-processor for detecting inner beans as ApplicationListeners,
// moving it to the end of the processor chain (for picking up proxies etc).
beanFactory.addBeanPostProcessor(new ApplicationListenerDetector(applicationContext));
}
⑨ AbstractRefreshableWebApplicationContext.onRefresh()
源码如下：
/**
* Initialize the theme capability.
*/
@Override
protected void onRefresh() {
this.themeSource = UiApplicationContextUtils.initThemeSource(this);
}
UiApplicationContextUtils.initThemeSource(this)如下：
/**
* Initialize the ThemeSource for the given application context,
* autodetecting a bean with the name "themeSource". If no such
* bean is found, a default (empty) ThemeSource will be used.
* @param context current application context
* @return the initialized theme source (will never be {@code null})
* @see #THEME_SOURCE_BEAN_NAME
*/
public static ThemeSource initThemeSource(ApplicationContext context) {
if (context.containsLocalBean(THEME_SOURCE_BEAN_NAME)) {
ThemeSource themeSource = context.getBean(THEME_SOURCE_BEAN_NAME, ThemeSource.class);
// Make ThemeSource aware of parent ThemeSource.
if (context.getParent() instanceof ThemeSource && themeSource instanceof HierarchicalThemeSource) {
HierarchicalThemeSource hts = (HierarchicalThemeSource) themeSource;
if (hts.getParentThemeSource() == null) {
// Only set parent context as parent ThemeSource if no parent ThemeSource
// registered already.
hts.setParentThemeSource((ThemeSource) context.getParent());
}
}
if (logger.isDebugEnabled()) {
logger.debug("Using ThemeSource [" + themeSource + "]");
}
return themeSource;
}
else {
// Use default ThemeSource to be able to accept getTheme calls, either
// delegating to parent context's default or to local ResourceBundleThemeSource.
HierarchicalThemeSource themeSource = null;
if (context.getParent() instanceof ThemeSource) {
themeSource = new DelegatingThemeSource();
themeSource.setParentThemeSource((ThemeSource) context.getParent());
}
else {
themeSource = new ResourceBundleThemeSource();
}
if (logger.isDebugEnabled()) {
logger.debug("Unable to locate ThemeSource with name '" + THEME_SOURCE_BEAN_NAME +
"': using default [" + themeSource + "]");
}
return themeSource;
}
}
(10)AbstractApplicationContext.registerListeners()
源码如下：
/**
* Add beans that implement ApplicationListener as listeners.
* Doesn't affect other listeners, which can be added without being beans.
*/
protected void registerListeners() {
// Register statically specified listeners first.
//把监听器放入应用事件广播器中
for (ApplicationListener<?> listener : getApplicationListeners()) {
getApplicationEventMulticaster().addApplicationListener(listener);
}
// Do not initialize FactoryBeans here: We need to leave all regular beans
// uninitialized to let post-processors apply to them!
//获取所有需要被监听的BeanName
String[] listenerBeanNames = getBeanNamesForType(ApplicationListener.class, true, false);
//遍历所有BeanName
for (String listenerBeanName : listenerBeanNames) {
// Add a listener bean to be notified of all events.
getApplicationEventMulticaster().addApplicationListenerBean(listenerBeanName);
}
// Publish early application events now that we finally have a multicaster...
Set<ApplicationEvent> earlyEventsToProcess = this.earlyApplicationEvents;
this.earlyApplicationEvents = null;
if (earlyEventsToProcess != null) {
for (ApplicationEvent earlyEvent : earlyEventsToProcess) {
//广播事件给监听
getApplicationEventMulticaster().multicastEvent(earlyEvent);
}
}
}
(11)AbstractApplicationContext.finishBeanFactoryInitialization()
/**
* Finish the initialization of this context's bean factory,
* initializing all remaining singleton beans.
*/
protected void finishBeanFactoryInitialization(ConfigurableListableBeanFactory beanFactory) {
// Initialize conversion service for this context.--conversionService
if (beanFactory.containsBean(CONVERSION_SERVICE_BEAN_NAME) &&
beanFactory.isTypeMatch(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class)) {
beanFactory.setConversionService(
beanFactory.getBean(CONVERSION_SERVICE_BEAN_NAME, ConversionService.class));
}
// Register a default embedded value resolver if no bean post-processor
// (such as a PropertyPlaceholderConfigurer bean) registered any before:
// at this point, primarily for resolution in annotation attribute values.
if (!beanFactory.hasEmbeddedValueResolver()) {
beanFactory.addEmbeddedValueResolver(strVal -> getEnvironment().resolvePlaceholders(strVal));
}
// Initialize LoadTimeWeaverAware beans early to allow for registering their transformers early.
String[] weaverAwareNames = beanFactory.getBeanNamesForType(LoadTimeWeaverAware.class, false, false);
for (String weaverAwareName : weaverAwareNames) {
getBean(weaverAwareName);
}
// Stop using the temporary ClassLoader for type matching.
beanFactory.setTempClassLoader(null);
// Allow for caching all bean definition metadata, not expecting further changes.
beanFactory.freezeConfiguration();
// Instantiate all remaining (non-lazy-init) singletons.
beanFactory.preInstantiateSingletons();
}
(12)AbstractApplicationContext.finishRefresh()
源码如下：
/**
* Finish the refresh of this context, invoking the LifecycleProcessor's
* onRefresh() method and publishing the
* {@link org.springframework.context.event.ContextRefreshedEvent}.
*/
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches();
// Initialize lifecycle processor for this context.
//Initialize the LifecycleProcessor.
//Uses DefaultLifecycleProcessor if none defined in the context.
initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
//首先将刷新传播到生命周期处理器
getLifecycleProcessor().onRefresh();
// Publish the final event.
//参考（13）
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}
(13)AbstractApplicationContext.publishEvent()
如下所示：
/**
* Publish the given event to all listeners.
* <p>Note: Listeners get initialized after the MessageSource, to be able
* to access it within listener implementations. Thus, MessageSource
* implementations cannot publish events.
* @param event the event to publish (may be application-specific or a
* standard framework event)
*/
@Override
public void publishEvent(ApplicationEvent event) {
publishEvent(event, null);
}
调用的publishEvent(event,null)如下所示：
protected void publishEvent(Object event, @Nullable ResolvableType eventType) {
Assert.notNull(event, "Event must not be null");
if (logger.isTraceEnabled()) {
logger.trace("Publishing event in " + getDisplayName() + ": " + event);
}
// Decorate event as an ApplicationEvent if necessary
ApplicationEvent applicationEvent;
if (event instanceof ApplicationEvent) {
applicationEvent = (ApplicationEvent) event;
}
else {
applicationEvent = new PayloadApplicationEvent<>(this, event);
if (eventType == null) {
eventType = ((PayloadApplicationEvent) applicationEvent).getResolvableType();
}
}
// Multicast right now if possible - or lazily once the multicaster is initialized
if (this.earlyApplicationEvents != null) {
this.earlyApplicationEvents.add(applicationEvent);
}
else {
//applicationEvent==ContextRefreshedEvent
//Multicast the given application event to appropriate listeners.
//If the eventType is null, a default type is builtbased on the event instance.
getApplicationEventMulticaster().multicastEvent(applicationEvent, eventType);
}
// Publish event via parent context as well...
if (this.parent != null) {
if (this.parent instanceof AbstractApplicationContext) {
((AbstractApplicationContext) this.parent).publishEvent(event, eventType);
}
else {
this.parent.publishEvent(event);
}
}
}
至此，Spring容器创建、配置并刷新完成！！！
【2】SpringMVC容器创建
SpringMVC的核心是DispatcherServlet，其是一个Servlet。首先要注意Servlet的三个标准方法：init(),service()和destroy()。
DispatcherServlet类继承如下：
DispatcherServlet是没有init()方法的，其继承父类HttpServletBean.init()方法。
DispatcherServlet也没有service()方法，其继承父类FrameworkServlet.service()方法。
这里主要研究这两个方法前后做了什么。
【3】HttpServletBean.init()
(1)SpringMVC容器创建
创建完IOC容器后就该创建SpringMVC容器。
首先Tomcat调用无参构造函数,初始化DispatcherServlet实例。StandardContext 实例化servlet之后,接着初始化该servlet。
DispatcherServlet自身没有init()方法，其继承自父类HttpServletBean，这时首先调用HttpServletBean.init()方法。
init 方法的执行时刻其实与 servlet 的配置有关。可以看到以下代码的load-on-startup结点，如果结点的值大于等于 0，则在 Servlet 实例化的时候执行，间隔时间由具体的值决定，值越大，则越迟执行。如果小于 0 或者没有配置，则在第一次请求的时候才同步执行 ， 注意 init 方法只执行一次。
<load-on-startup>1</load-on-startup>
HttpServletBean.init()源码如下：
@Override
public final void init() throws ServletException {
if (logger.isDebugEnabled()) {
logger.debug("Initializing servlet '" + getServletName() + "'");
}
// Set bean properties from init parameters.
PropertyValues pvs = new ServletConfigPropertyValues(getServletConfig(), this.requiredProperties);
if (!pvs.isEmpty()) {
try {
BeanWrapper bw = PropertyAccessorFactory.forBeanPropertyAccess(this);
ResourceLoader resourceLoader = new ServletContextResourceLoader(getServletContext());
bw.registerCustomEditor(Resource.class, new ResourceEditor(resourceLoader, getEnvironment()));
initBeanWrapper(bw);
bw.setPropertyValues(pvs, true);
}
catch (BeansException ex) {
if (logger.isErrorEnabled()) {
logger.error("Failed to set bean properties on servlet '" + getServletName() + "'", ex);
}
throw ex;
}
}
// Let subclasses do whatever initialization they like.
//这里我们要关注这个！FrameworkServlet.initServletBean() --参考2
initServletBean();
if (logger.isDebugEnabled()) {
logger.debug("Servlet '" + getServletName() + "' configured successfully");
}
}
(2) FrameworkServlet.initServletBean()
然后开始执行FrameworkServlet.initServletBean() 方法，其重写了父类HttpServletBean.initServletBean方法，源码如下：
Overridden method of {@link HttpServletBean}, invoked after any bean properties have been set. Creates this servlet’s WebApplicationContext.
@Override
protected final void initServletBean() throws ServletException {
getServletContext().log("Initializing Spring FrameworkServlet '" + getServletName() + "'");
if (this.logger.isInfoEnabled()) {
this.logger.info("FrameworkServlet '" + getServletName() + "': initialization started");
}
long startTime = System.currentTimeMillis();
try {
// 初始化WebApplicationContext--参考3
this.webApplicationContext = initWebApplicationContext();
//初始化FrameworkServlet--参考4
initFrameworkServlet();
}
catch (ServletException ex) {
this.logger.error("Context initialization failed", ex);
throw ex;
}
catch (RuntimeException ex) {
this.logger.error("Context initialization failed", ex);
throw ex;
}
if (this.logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
this.logger.info("FrameworkServlet '" + getServletName() + "': initialization completed in " +
elapsedTime + " ms");
}
}
这段代码很重要，先初始化WebApplicationContext，然后初始化FrameworkServlet！
(3)FrameworkServlet.initWebApplicationContext()
Initialize and publish the WebApplicationContext for this servlet.
源码如下：
protected WebApplicationContext initWebApplicationContext() {
// 根据xml获取Root WebApplicationContext--XmlWebApplicationContext
//现获取父容器
WebApplicationContext rootContext =
WebApplicationContextUtils.getWebApplicationContext(getServletContext());
WebApplicationContext wac = null;
//判断项目中是否已经存在DispatcherServlet.webApplicationContext
if (this.webApplicationContext != null) {
// A context instance was injected at construction time -> use it
wac = this.webApplicationContext;
if (wac instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) wac;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent -> set
// the root application context (if any; may be null) as the parent
cwac.setParent(rootContext);
}
configureAndRefreshWebApplicationContext(cwac);
}
}
}
if (wac == null) {
// No context instance was injected at construction time -> see if one
// has been registered in the servlet context. If one exists, it is assumed
// that the parent context (if any) has already been set and that the
// user has performed any initialization such as setting the context id
wac = findWebApplicationContext();
//尝试从servlet context 查找一个WebApplicationContext--3.1
}
if (wac == null) {
// No context instance is defined for this servlet -> create a local one
wac = createWebApplicationContext(rootContext);
//根据rootContext创建一个WebApplicationContext--3.2
}
/** Flag used to detect whether onRefresh has already been called */
// private boolean refreshEventReceived = false;
if (!this.refreshEventReceived) {
// Either the context is not a ConfigurableApplicationContext with refresh
// support or the context injected at construction time had already been
// refreshed -> trigger initial onRefresh manually here.
onRefresh(wac);
//这个方法很重要！！！
}
//使用属性org.springframework.web.servlet.FrameworkServlet.CONTEXT.springMVC
//放到org.apache.catalina.core.ApplicationContext中
if (this.publishContext) {
// Publish the context as a servlet context attribute.
String attrName = getServletContextAttributeName();
getServletContext().setAttribute(attrName, wac);
if (this.logger.isDebugEnabled()) {
this.logger.debug("Published WebApplicationContext of servlet '" + getServletName() +
"' as ServletContext attribute with name [" + attrName + "]");
}
}
return wac;
}
获取根容器源码如下：
WebApplicationContextUtils.getWebApplicationContext
@Nullable
public static WebApplicationContext getWebApplicationContext(ServletContext sc) {
return getWebApplicationContext(sc, WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
}
//ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE：
//org.springframework.web.context.WebApplicationContext.ROOT
(3.1)FrameworkServlet.findWebApplicationContext()方法
Retrieve a {@code WebApplicationContext} from the {@code ServletContext} attribute with the {@link #setContextAttribute configured name}。
@Nullable
protected WebApplicationContext findWebApplicationContext() {
String attrName = getContextAttribute();
if (attrName == null) {
return null;
}
WebApplicationContext wac =
WebApplicationContextUtils.getWebApplicationContext(getServletContext(), attrName);
if (wac == null) {
throw new IllegalStateException("No WebApplicationContext found: initializer not registered?");
}
return wac;
}
(3.2)createWebApplicationContext
Instantiate the WebApplicationContext for this servlet, either a default {@link org.springframework.web.context.support.XmlWebApplicationContext} or a {@link #setContextClass custom context class}, if set.
This implementation expects custom contexts to implement the {@link org.springframework.web.context.ConfigurableWebApplicationContext} interface. Can be overridden in subclasses.
Do not forget to register this servlet instance as application listener on the created context (for triggering its {@link #onRefresh callback}, and to call {@link org.springframework.context.ConfigurableApplicationContext#refresh()} before returning the context instance.
源码如下：
protected WebApplicationContext createWebApplicationContext(@Nullable ApplicationContext parent) {
//org.springframework.web.context.support.XmlWebApplicationContext
Class<?> contextClass = getContextClass();
if (this.logger.isDebugEnabled()) {
this.logger.debug("Servlet with name '" + getServletName() +
"' will try to create custom WebApplicationContext context of class '" +
contextClass.getName() + "'" + ", using parent context [" + parent + "]");
}
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException(
"Fatal initialization error in servlet with name '" + getServletName() +
"': custom WebApplicationContext class [" + contextClass.getName() +
"] is not of type ConfigurableWebApplicationContext");
}
//根据contextClass获取实例并强转为ConfigurableWebApplicationContext
ConfigurableWebApplicationContext wac =
(ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
//设置环境
wac.setEnvironment(getEnvironment());
//设置父容器--initWebApplicationContext里面的rootContext
wac.setParent(parent);
//配置文件路径classpath:spring-mvc.xml
String configLocation = getContextConfigLocation();
if (configLocation != null) {
wac.setConfigLocation(configLocation);
}
//配置并刷新创建的wac-3.3
configureAndRefreshWebApplicationContext(wac);
return wac;
}
(3.3)configureAndRefreshWebApplicationContext
源码如下：
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac) {
//设置id：org.springframework.web.context.WebApplicationContext:/springMVC
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
if (this.contextId != null) {
wac.setId(this.contextId);
}
else {
// Generate default id...
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(getServletContext().getContextPath()) + '/' + getServletName());
}
}
wac.setServletContext(getServletContext());
wac.setServletConfig(getServletConfig());
//setNamespace：springMVC-servlet
wac.setNamespace(getNamespace());
//添加监听
wac.addApplicationListener(new SourceFilteringListener(wac, new ContextRefreshListener()));
// The wac environment's #initPropertySources will be called in any case when the context
// is refreshed; do it eagerly here to ensure servlet property sources are in place for
// use in any post-processing or initialization that occurs below prior to #refresh
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(getServletContext(), getServletConfig());
}
//在刷新和激活该servlet的上下文之前，对给定的wac进行后期处理。默认空方法
postProcessWebApplicationContext(wac);
//参考 3.4
applyInitializers(wac);
//参考3.5
wac.refresh();
}
(3.4)applyInitializers
Delegate the WebApplicationContext before it is refreshed to any {@link ApplicationContextInitializer} instances specified by the “contextInitializerClasses” servlet init-param.
源码如下：
protected void applyInitializers(ConfigurableApplicationContext wac) {
String globalClassNames = getServletContext().getInitParameter(ContextLoader.GLOBAL_INITIALIZER_CLASSES_PARAM);
if (globalClassNames != null) {
for (String className : StringUtils.tokenizeToStringArray(globalClassNames, INIT_PARAM_DELIMITERS)) {
this.contextInitializers.add(loadInitializer(className, wac));
}
}
if (this.contextInitializerClasses != null) {
for (String className : StringUtils.tokenizeToStringArray(this.contextInitializerClasses, INIT_PARAM_DELIMITERS)) {
this.contextInitializers.add(loadInitializer(className, wac));
}
}
AnnotationAwareOrderComparator.sort(this.contextInitializers);
for (ApplicationContextInitializer<ConfigurableApplicationContext> initializer : this.contextInitializers) {
initializer.initialize(wac);
}
}
(3.5)AbstractApplicationContext.refresh()
再次调用AbstractApplicationContext.refresh()！上面创建Root WebApplicationContext时最后一步就调用了该方法！
这里需要注意的是在 wac.refresh()方法中，有个方法调用至关重要：
//registerApplicationContext
publishEvent(new ContextRefreshedEvent(this));
因为FrameWorkServelt有个私有内部类ContextRefreshListener ：
/**
* ApplicationListener endpoint that receives events from this servlet's WebApplicationContext
* only, delegating to {@code onApplicationEvent} on the FrameworkServlet instance.
*/
private class ContextRefreshListener implements ApplicationListener<ContextRefreshedEvent> {
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
//参考（3.6）
FrameworkServlet.this.onApplicationEvent(event);
}
}
(3.6)FrameworkServlet.onApplicationEvent()
其源码如下：
/**
* Callback that receives refresh events from this servlet's WebApplicationContext.
* <p>The default implementation calls {@link #onRefresh},
* triggering a refresh of this servlet's context-dependent state.
* @param event the incoming ApplicationContext event
*/
public void onApplicationEvent(ContextRefreshedEvent event) {
this.refreshEventReceived = true;
//参考（3.7）
onRefresh(event.getApplicationContext());
}
(3.7)DispatcherServlet.onRefresh()
源码如下：
/**
* This implementation calls {@link #initStrategies}.
*/
@Override
protected void onRefresh(ApplicationContext context) {
//初始化策略--参考（3.8）
initStrategies(context);
}
(3.8)DispatcherServlet.initStrategies()
源码如下：
/**
* Initialize the strategy objects that this servlet uses.
* <p>May be overridden in subclasses in order to initialize further strategy objects.
*/
protected void initStrategies(ApplicationContext context) {
// 上传文件的那个玩意
initMultipartResolver(context);
//根据beanName--localeResolver从BeanFactory获取LocaleResolver
//否则返回默认org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver
initLocaleResolver(context);
//根据beanName--themeResolver从BeanFactory获取
//否则返回默认org.springframework.web.servlet.theme.FixedThemeResolver
initThemeResolver(context);
//Initialize the HandlerMappings used by this class.
//默认BeanNameUrlHandlerMapping
initHandlerMappings(context);
//Initialize the HandlerAdapters used by this class.
//默认SimpleControllerHandlerAdapter
initHandlerAdapters(context);
//Initialize the HandlerExceptionResolver used by this class.
//we default to no exception resolver.
initHandlerExceptionResolvers(context);
//初始化请求视图转换器
//根据beanName--viewNameTranslator从工厂获取
//否则返回默认对象DefaultRequestToViewNameTranslator
initRequestToViewNameTranslator(context);
//Initialize the ViewResolvers used by this class.
//default to InternalResourceViewResolver
initViewResolvers(context);
//根据beanName-flashMapManager从工厂里面获取
//默认DefaultFlashMapManager
initFlashMapManager(context);
}
之后，依次返回3.7,3.6…直到AbstractApplicationContext.publishEvent方法。
方法如下：
/**
* Publish the given event to all listeners.
* @param event the event to publish (may be an {@link ApplicationEvent}
* or a payload object to be turned into a {@link PayloadApplicationEvent})
* @param eventType the resolved event type, if known
* @since 4.2
*/
protected void publishEvent(Object event, @Nullable ResolvableType eventType) {
Assert.notNull(event, "Event must not be null");
if (logger.isTraceEnabled()) {
logger.trace("Publishing event in " + getDisplayName() + ": " + event);
}
// Decorate event as an ApplicationEvent if necessary
ApplicationEvent applicationEvent;
if (event instanceof ApplicationEvent) {
applicationEvent = (ApplicationEvent) event;
}
else {
applicationEvent = new PayloadApplicationEvent<>(this, event);
if (eventType == null) {
eventType = ((PayloadApplicationEvent) applicationEvent).getResolvableType();
}
}
// Multicast right now if possible - or lazily once the multicaster is initialized
if (this.earlyApplicationEvents != null) {
this.earlyApplicationEvents.add(applicationEvent);
}
else {
getApplicationEventMulticaster().multicastEvent(applicationEvent, eventType);
}
// Publish event via parent context as well...
//在Spring容器创建过程中，该步跳过了。但是现在SpringMVC父容器为Spring容器！！！
if (this.parent != null) {
if (this.parent instanceof AbstractApplicationContext) {
//调用该方法--参考（3.9）
((AbstractApplicationContext) this.parent).publishEvent(event, eventType);
}
else {
this.parent.publishEvent(event);
}
}
}
(3.9)SimpleApplicationEventMulticaster.multicastEvent
@Override
public void multicastEvent(final ApplicationEvent event, @Nullable ResolvableType eventType) {
ResolvableType type = (eventType != null ? eventType : resolveDefaultEventType(event));
for (final ApplicationListener<?> listener : getApplicationListeners(event, type)) {
Executor executor = getTaskExecutor();
if (executor != null) {
executor.execute(() -> invokeListener(listener, event));
}
else {
//调用该方法....
invokeListener(listener, event);
}
}
}
也就是说Spring容器创建过程中调用了一遍AbstractApplicationContext.publishEvent()方法，SpringIOC容器创建过程中调用了两遍AbstractApplicationContext.publishEvent()方法！！
此时FrameworkServlet.configureAndRefreshWebApplicationContext()方法才算结束！返回到（3.2）
(4)initFrameworkServlet
前面初始化了Spring容器和SpringMVC容器，这里初始化FrameworkServlet。
源码如下：
/**
* This method will be invoked after any bean properties have been set and
* the WebApplicationContext has been loaded. The default implementation is empty;
* subclasses may override this method to perform any initialization they require.
* @throws ServletException in case of an initialization exception
*/
protected void initFrameworkServlet() throws ServletException {
}
【4】DispatcherServlet运行原理分析
一个Servlet在处理请求的时候具体方法为service，DispatcherServlet继承自父类FrameworkServlet.service()方法。
这里以浏览器发送get请求为例 http://localhost:8080/login。
① FrameworkServlet.service()
源码如下：
@Override
protected void service(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//参考（2）
HttpMethod httpMethod = HttpMethod.resolve(request.getMethod());
// 进行方法判断
if (HttpMethod.PATCH == httpMethod || httpMethod == null) {
//请求处理
processRequest(request, response);
}
else {
//参考（3）
super.service(request, response);
}
}
首先获取方法，然后处理请求。
② 获取请求方法
首先获取方法类型名字：
Request.getMethod()：
/**
* Return the HTTP request method used in this Request.
*/
@Override
public String getMethod() {
return coyoteRequest.method().toString();
}
其次解析方法名获取HttpMethod：
③ HttpServlet.service()方法
源码如下：
protected void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String method = req.getMethod();
// 这里将会走doGet方法，参考（4）
if (method.equals(METHOD_GET)) {
long lastModified = getLastModified(req);
if (lastModified == -1) {
// servlet doesn't support if-modified-since, no reason
// to go through further expensive logic
doGet(req, resp);
} else {
long ifModifiedSince;
try {
ifModifiedSince = req.getDateHeader(HEADER_IFMODSINCE);
} catch (IllegalArgumentException iae) {
// Invalid date header - proceed as if none was set
ifModifiedSince = -1;
}
if (ifModifiedSince < (lastModified / 1000 * 1000)) {
// If the servlet mod time is later, call doGet()
// Round down to the nearest second for a proper compare
// A ifModifiedSince of -1 will always be less
maybeSetLastModified(resp, lastModified);
doGet(req, resp);
} else {
resp.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
}
}
} else if (method.equals(METHOD_HEAD)) {
long lastModified = getLastModified(req);
maybeSetLastModified(resp, lastModified);
doHead(req, resp);
} else if (method.equals(METHOD_POST)) {
doPost(req, resp);
} else if (method.equals(METHOD_PUT)) {
doPut(req, resp);
} else if (method.equals(METHOD_DELETE)) {
doDelete(req, resp);
} else if (method.equals(METHOD_OPTIONS)) {
doOptions(req,resp);
} else if (method.equals(METHOD_TRACE)) {
doTrace(req,resp);
} else {
//
// Note that this means NO servlet supports whatever
// method was requested, anywhere on this server.
//
String errMsg = lStrings.getString("http.method_not_implemented");
Object[] errArgs = new Object[1];
errArgs[0] = method;
errMsg = MessageFormat.format(errMsg, errArgs);
resp.sendError(HttpServletResponse.SC_NOT_IMPLEMENTED, errMsg);
}
}
④ FrameworkServlet.doGet方法
@Override
protected final void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//参考 （5）
processRequest(request, response);
}
⑤ FrameworkServlet.processRequest()方法
请求处理的核心方法：
/**
* Process this request, publishing an event regardless of the outcome.
* <p>The actual event handling is performed by the abstract
* {@link #doService} template method.
*/
protected final void processRequest(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
long startTime = System.currentTimeMillis();
Throwable failureCause = null;
LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext();
LocaleContext localeContext = buildLocaleContext(request);
RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes();
ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes);
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor());
initContextHolders(request, localeContext, requestAttributes);
try {
// 核心方法 参考（6）
doService(request, response);
}
catch (ServletException | IOException ex) {
failureCause = ex;
throw ex;
}
catch (Throwable ex) {
failureCause = ex;
throw new NestedServletException("Request processing failed", ex);
}
finally {
resetContextHolders(request, previousLocaleContext, previousAttributes);
if (requestAttributes != null) {
requestAttributes.requestCompleted();
}
if (logger.isDebugEnabled()) {
if (failureCause != null) {
this.logger.debug("Could not complete request", failureCause);
}
else {
if (asyncManager.isConcurrentHandlingStarted()) {
logger.debug("Leaving response open for concurrent processing");
}
else {
this.logger.debug("Successfully completed request");
}
}
}
//发布请求已经被处理事件 参考 （14）
publishRequestHandledEvent(request, response, startTime, failureCause);
}
}
⑥ DispatcherServlet.doService()方法
源码如下：
/**
* Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch}
* for the actual dispatching.
*/
@Override
protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception {
if (logger.isDebugEnabled()) {
String resumed = WebAsyncUtils.getAsyncManager(request).hasConcurrentResult() ? " resumed" : "";
logger.debug("DispatcherServlet with name '" + getServletName() + "'" + resumed +
" processing " + request.getMethod() + " request for [" + getRequestUri(request) + "]");
}
// Keep a snapshot of the request attributes in case of an include,
// to be able to restore the original attributes after the include.
Map<String, Object> attributesSnapshot = null;
if (WebUtils.isIncludeRequest(request)) {
attributesSnapshot = new HashMap<>();
Enumeration<?> attrNames = request.getAttributeNames();
while (attrNames.hasMoreElements()) {
String attrName = (String) attrNames.nextElement();
if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) {
attributesSnapshot.put(attrName, request.getAttribute(attrName));
}
}
}
// Make framework objects available to handlers and view objects.
request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext());
request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver);
request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver);
request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource());
if (this.flashMapManager != null) {
FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response);
if (inputFlashMap != null) {
request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap));
}
request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap());
request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager);
}
try {
// 哈哈，在这里 参考（7）
doDispatch(request, response);
}
finally {
if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Restore the original attribute snapshot, in case of an include.
if (attributesSnapshot != null) {
restoreAttributesAfterInclude(request, attributesSnapshot);
}
}
}
}
⑦ DispatcherServlet.doDispatch()
源码如下：
/**
* Process the actual dispatching to the handler.
* <p>The handler will be obtained by applying the servlet's HandlerMappings in order.
* The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters
* to find the first that supports the handler class.
* <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers
* themselves to decide which methods are acceptable.
* @param request current HTTP request
* @param response current HTTP response
* @throws Exception in case of any kind of processing failure
*/
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
//处理器链
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
//视图对象
ModelAndView mv = null;
//异常对象
Exception dispatchException = null;
try {
//使用multipartResolver检测request是否为a multipart request；
//如果是，则解析为 multipart request
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
//根据当前请求，或者处理器链 参考⑧
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
//根据HandlerExecutionChain 的Handler对象，获取HandlerAdapter 对象
//参考 ⑨
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
// Process last-modified header, if supported by the handler.
String method = request.getMethod();
boolean isGet = "GET".equals(method);
if (isGet || "HEAD".equals(method)) {
long lastModified = ha.getLastModified(request, mappedHandler.getHandler());
if (logger.isDebugEnabled()) {
logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);
}
if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
//执行HandlerExecutionChain中每个拦截器的preHandle方法
if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
//核心方法！！！获取MAV 参考 （10）
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
//执行handlerExecutionChain中拦截器的postHandle()方法
mappedHandler.applyPostHandle(processedRequest, response, mv);
}
catch (Exception ex) {
dispatchException = ex;
}
catch (Throwable err) {
// As of 4.3, we're processing Errors thrown from handler methods as well,
// making them available for @ExceptionHandler methods and other scenarios.
dispatchException = new NestedServletException("Handler dispatch failed", err);
}
//处理器处理结果 参考（11）
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
}
catch (Exception ex) {
triggerAfterCompletion(processedRequest, response, mappedHandler, ex);
}
catch (Throwable err) {
triggerAfterCompletion(processedRequest, response, mappedHandler,
new NestedServletException("Handler processing failed", err));
}
finally {
if (asyncManager.isConcurrentHandlingStarted()) {
// Instead of postHandle and afterCompletion
if (mappedHandler != null) {
mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);
}
}
else {
// Clean up any resources used by a multipart request.
if (multipartRequestParsed) {
cleanupMultipart(processedRequest);
}
}
}
}
⑧DispatcherServlet.getHandler()
@Nullable
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
if (this.handlerMappings != null) {
for (HandlerMapping hm : this.handlerMappings) {
if (logger.isTraceEnabled()) {
logger.trace(
"Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'");
}
//根据hanlerMapping和请求获取HandlerExecutionChain ，参考（8.1）
HandlerExecutionChain handler = hm.getHandler(request);
if (handler != null) {
return handler;
}
}
}
return null;
}
(8.1)AbstractHandlerMapping.getHandler()
源码如下：
/**
* Look up a handler for the given request, falling back to the default
* handler if no specific one is found.
* @param request current HTTP request
* @return the corresponding handler instance, or the default handler
* @see #getHandlerInternal
*/
@Override
@Nullable
public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {
//获取handler 参考（8.3）
Object handler = getHandlerInternal(request);
if (handler == null) {
handler = getDefaultHandler();
}
if (handler == null) {
return null;
}
// Bean name or resolved handler?
if (handler instanceof String) {
String handlerName = (String) handler;
handler = obtainApplicationContext().getBean(handlerName);
}
// 根据handler和请求，获取HandlerExecutionChain 参考（8.6）
HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request);
if (CorsUtils.isCorsRequest(request)) {
CorsConfiguration globalConfig = this.globalCorsConfigSource.getCorsConfiguration(request);
CorsConfiguration handlerConfig = getCorsConfiguration(handler, request);
CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig);
executionChain = getCorsHandlerExecutionChain(request, executionChain, config);
}
return executionChain;
}
(8.3)AbstractHandlerMethodMapping.getHandlerInternal()
源码如下：
/**
* Look up a handler method for the given request.
*/
@Override
protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception {
//找到请求的url 本例这里为 /login
String lookupPath = getUrlPathHelper().getLookupPathForRequest(request);
if (logger.isDebugEnabled()) {
logger.debug("Looking up handler method for path " + lookupPath);
}
//获取mappingRegistry的读锁
this.mappingRegistry.acquireReadLock();
try {
// 查找处理方法 参考（8.4）
HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request);
if (logger.isDebugEnabled()) {
if (handlerMethod != null) {
logger.debug("Returning handler method [" + handlerMethod + "]");
}
else {
logger.debug("Did not find handler method for [" + lookupPath + "]");
}
}
// 这里很有意思 参考8.5
return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null);
}
finally {
//释放读锁
this.mappingRegistry.releaseReadLock();
}
}
(8.4)AbstractHandlerMethodMapping.lookupHandlerMethod()
源码如下：
/**
* Look up the best-matching handler method for the current request.
* If multiple matches are found, the best match is selected.
* @param lookupPath mapping lookup path within the current servlet mapping
* @param request the current request
* @return the best-matching handler method, or {@code null} if no match
* @see #handleMatch(Object, String, HttpServletRequest)
* @see #handleNoMatch(Set, String, HttpServletRequest)
*/
@Nullable
protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception {
List<Match> matches = new ArrayList<>();
//A registry that maintains all mappings to handler methods, exposing methods to perform lookups and providing concurrent access.
// 这里为[{[/login]}]
List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath);
//如果directPathMatches不为null，就向matches添加
//matches.add(new Match(match, this.mappingRegistry.getMappings().get(mapping)));
//match 为RequestMappingInfo 对象
if (directPathMatches != null) {
addMatchingMappings(directPathMatches, matches, request);
}
if (matches.isEmpty()) {
// No choice but to go through all mappings...
addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request);
}
if (!matches.isEmpty()) {
Comparator<Match> comparator = new MatchComparator(getMappingComparator(request));
//使用工具类进行排序
Collections.sort(matches, comparator);
if (logger.isTraceEnabled()) {
logger.trace("Found " + matches.size() + " matching mapping(s) for [" +
lookupPath + "] : " + matches);
}
//获取排序后的最好的Match对象
Match bestMatch = matches.get(0);
if (matches.size() > 1) {
if (CorsUtils.isPreFlightRequest(request)) {
return PREFLIGHT_AMBIGUOUS_MATCH;
}
//获取第二个最好的Match对象
Match secondBestMatch = matches.get(1);
if (comparator.compare(bestMatch, secondBestMatch) == 0) {
Method m1 = bestMatch.handlerMethod.getMethod();
Method m2 = secondBestMatch.handlerMethod.getMethod();
throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" +
request.getRequestURL() + "': {" + m1 + ", " + m2 + "}");
}
}
//Expose URI template variables, matrix variables, and producible media types in the request
handleMatch(bestMatch.mapping, lookupPath, request);
//将HandlerMethod对象返回
return bestMatch.handlerMethod;
}
else {
return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request);
}
}
其中matches为一个链表，存放Match对象，每个Match对象由(T)Mapping对象和HandlerMethod对象组成，如下图所示：
其中HandlerMethod包含了方法相关的详细信息，如下所示：
有方法名、URL、返回类型，参数值即方法上面的注解等等！
(8.5)HandlerMethod.createWithResolvedBean()方法
源码如下：
/**
* If the provided instance contains a bean name rather than an object instance,
* the bean name is resolved before a {@link HandlerMethod} is created and returned.
*/
public HandlerMethod createWithResolvedBean() {
Object handler = this.bean;
if (this.bean instanceof String) {
Assert.state(this.beanFactory != null, "Cannot resolve bean name without BeanFactory");
String beanName = (String) this.bean;
//根据beanName从工厂里面返回一个bean--本例为LoginController
handler = this.beanFactory.getBean(beanName);
}
// 返回一个新的HandlerMethod对象
return new HandlerMethod(this, handler);
}
(8.6)AbstractHandlerMapping.getHandlerExecutionChain()方法
源码如下：
protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {
//获取一个HandlerExecutionChain
HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ?
(HandlerExecutionChain) handler : new HandlerExecutionChain(handler));
//根据请求url，获取匹配的拦截器
String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);
for (HandlerInterceptor interceptor : this.adaptedInterceptors) {
if (interceptor instanceof MappedInterceptor) {
MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor;
if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) {
//向chain中添加interceptor
chain.addInterceptor(mappedInterceptor.getInterceptor());
}
}
else {
chain.addInterceptor(interceptor);
}
}
return chain;
}
⑨ DispatcherServlet.getHandlerAdapter()方法
源码如下：
/**
* Return the HandlerAdapter for this handler object.
* @param handler the handler object to find an adapter for
* @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error.
*/
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {
if (this.handlerAdapters != null) {
//遍历初始化的所有handlerAdapters找到合适的一个并返回
for (HandlerAdapter ha : this.handlerAdapters) {
if (logger.isTraceEnabled()) {
logger.trace("Testing handler adapter [" + ha + "]");
}
//判断是否支持 本例这里返回的是RequestMappingHandlerAdapter
if (ha.supports(handler)) {
return ha;
}
}
}
throw new ServletException("No adapter for handler [" + handler +
"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler");
}
(10)AbstractHandlerMethodAdapter.handle()方法
源码如下：
/**
* This implementation expects the handler to be an {@link HandlerMethod}.
*/
@Override
@Nullable
public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
throws Exception {
//参考 （10.1）
return handleInternal(request, response, (HandlerMethod) handler);
}
(10.1)RequestMappingHandlerAdapter.handleInternal()方法
源码如下：
@Override
protected ModelAndView handleInternal(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ModelAndView mav;
checkRequest(request);
// Execute invokeHandlerMethod in synchronized block if required.
if (this.synchronizeOnSession) {
HttpSession session = request.getSession(false);
if (session != null) {
Object mutex = WebUtils.getSessionMutex(session);
synchronized (mutex) {
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// No HttpSession available -> no mutex necessary
mav = invokeHandlerMethod(request, response, handlerMethod);
}
}
else {
// No synchronization on session demanded at all...
//参考（10.2）
mav = invokeHandlerMethod(request, response, handlerMethod);
}
if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
}
else {
prepareResponse(response);
}
}
return mav;
}
(10.2)RequestMappingHandlerAdapter.invokeHandlerMethod()方法
源码如下：
@Nullable
protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {
ServletWebRequest webRequest = new ServletWebRequest(request, response);
try {
//数据绑定工厂，本例这里为ServletRequestDataBinderFactory
WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);
//ModelFactory(attrMethods, binderFactory, sessionAttrHandler)
ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);
ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
//如果参数处理器不为null，则为invocableMethod 设置参数处理器；
//本例这里参数处理器为HandlerMethodArgumentResolverComposite
if (this.argumentResolvers != null) {
invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
}
//如果返回值处理器不为null，则为invocableMethod 设置返回值处理器
//本例这里返回值处理器为HandlerMethodReturnValueHandlerComposite
if (this.returnValueHandlers != null) {
invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
}
//为invocableMethod设置数据绑定工厂
invocableMethod.setDataBinderFactory(binderFactory);
//为invocableMethod设置参数名发现器
//本例这里为DefaultParameterNameDiscoverer
invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);
//创建ModelAndViewContainer
ModelAndViewContainer mavContainer = new ModelAndViewContainer();
mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
/**
Populate the model in the following order:
1.Retrieve "known" session attributes listed as @SessionAttributes.
2.Invoke @ModelAttribute methods
3.Find @ModelAttribute method arguments also listed as @SessionAttributes and ensure they're present in the model raisingan exception if necessary.
*/
modelFactory.initModel(webRequest, mavContainer, invocableMethod);
mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);
AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);
asyncWebRequest.setTimeout(this.asyncRequestTimeout);
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
asyncManager.setTaskExecutor(this.taskExecutor);
asyncManager.setAsyncWebRequest(asyncWebRequest);
asyncManager.registerCallableInterceptors(this.callableInterceptors);
asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);
if (asyncManager.hasConcurrentResult()) {
Object result = asyncManager.getConcurrentResult();
mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];
asyncManager.clearConcurrentResult();
if (logger.isDebugEnabled()) {
logger.debug("Found concurrent result value [" + result + "]");
}
invocableMethod = invocableMethod.wrapConcurrentResult(result);
}
//要开始解析参数并处理实际目标方法了 参考（10.3）
invocableMethod.invokeAndHandle(webRequest, mavContainer);
if (asyncManager.isConcurrentHandlingStarted()) {
return null;
}
//获取ModelAndView并返回，参考（10.7）
return getModelAndView(mavContainer, modelFactory, webRequest);
}
finally {
webRequest.requestCompleted();
}
}
(10.3)ServletInvocableHandlerMethod.invokeAndHandle()
源码如下：
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
//执行目标方法，获取返回值 参考 （10.4）
Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);
setResponseStatus(webRequest);
//判断返回值是否为null，如果为null mavContainer.setRequestHandled(true);不再进行视图解析
if (returnValue == null) {
if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {
/* Whether the request has been handled fully within the handler, e.g. @ResponseBody method, and therefore view resolution is notnecessary.
This flag can also be set when controller methods declare anargument of type ServletResponse or OutputStream).
The default value is false.*/
mavContainer.setRequestHandled(true);
return;
}
}
else if (StringUtils.hasText(getResponseStatusReason())) {
mavContainer.setRequestHandled(true);
return;
}
//设置为false，说明需要进行视图解析-视图渲染
mavContainer.setRequestHandled(false);
//断言
Assert.state(this.returnValueHandlers != null, "No return value handlers");
try {
//使用返回值处理器处理返回值
//本例这里为HandlerMethodReturnValueHandlerComposite
//参考（10.5）
this.returnValueHandlers.handleReturnValue(
returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
}
catch (Exception ex) {
if (logger.isTraceEnabled()) {
logger.trace(getReturnValueHandlingErrorMessage("Error handling return value", returnValue), ex);
}
throw ex;
}
}
(10.4).InvocableHandlerMethod.invokeForRequest()
Invoke the method after resolving its argument values in the context of the given request.Argument values are commonly resolved through {@link HandlerMethodArgumentResolver}s.
源码如下：
public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
Object... providedArgs) throws Exception {
//获取方法参数
Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
if (logger.isTraceEnabled()) {
logger.trace("Invoking '" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +
"' with arguments " + Arrays.toString(args));
}
//执行实际目标方法，并获取返回值
//本例这里获取的返回值：ModelAndView: reference to view with name 'login'; model is null
Object returnValue = doInvoke(args);
if (logger.isTraceEnabled()) {
logger.trace("Method [" + ClassUtils.getQualifiedMethodName(getMethod(), getBeanType()) +
"] returned [" + returnValue + "]");
}
return returnValue;
}
(10.5)HandlerMethodReturnValueHandlerComposite.handleReturnValue()
源码如下：
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
//获取返回值处理器，本例这里为ModelAndViewMethodReturnValueHandler
HandlerMethodReturnValueHandler handler = selectHandler(returnValue, returnType);
if (handler == null) {
throw new IllegalArgumentException("Unknown return value type: " + returnType.getParameterType().getName());
}
//返回值处理，参考（10.6）
handler.handleReturnValue(returnValue, returnType, mavContainer, webRequest);
}
(10.6).ModelAndViewMethodReturnValueHandler.handleReturnValue()
源码如下：
@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest) throws Exception {
//如果返回值为null 直接返回
if (returnValue == null) {
mavContainer.setRequestHandled(true);
return;
}
//将返回值对象强转为ModelAndView
ModelAndView mav = (ModelAndView) returnValue;
//Return whether we use a view reference, i.e. true if the view has been specified via a
//name to be resolved by the DispatcherServlet via a ViewResolver.
if (mav.isReference()) {
//获取视图名，本例这里为"login"
String viewName = mav.getViewName();
mavContainer.setViewName(viewName);
//是否重定向
if (viewName != null && isRedirectViewName(viewName)) {
mavContainer.setRedirectModelScenario(true);
}
}
else {
View view = mav.getView();
mavContainer.setView(view);
if (view instanceof SmartView) {
if (((SmartView) view).isRedirectView()) {
mavContainer.setRedirectModelScenario(true);
}
}
}
mavContainer.setStatus(mav.getStatus());
//返回值对象里面的model放到mavContainer
mavContainer.addAllAttributes(mav.getModel());
}
(10.7)RequestMappingHandlerAdapter.getModelAndView()
源码如下：
private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,
ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception {
//Promote model attributes listed as {@code @SessionAttributes} to the session.
// Add {@link BindingResult} attributes where necessary.
modelFactory.updateModel(webRequest, mavContainer);
if (mavContainer.isRequestHandled()) {
return null;
}
ModelMap model = mavContainer.getModel();
ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());
if (!mavContainer.isViewReference()) {
mav.setView((View) mavContainer.getView());
}
if (model instanceof RedirectAttributes) {
Map<String, ?> flashAttributes = ((RedirectAttributes) model).getFlashAttributes();
HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);
if (request != null) {
RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);
}
}
return mav;
}
(11)DispatcherServlet.processDispatchResult()
源码如下：
private void processDispatchResult(HttpServletRequest request, HttpServletResponse response,
@Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv,
@Nullable Exception exception) throws Exception {
boolean errorView = false;
if (exception != null) {
if (exception instanceof ModelAndViewDefiningException) {
logger.debug("ModelAndViewDefiningException encountered", exception);
mv = ((ModelAndViewDefiningException) exception).getModelAndView();
}
else {
Object handler = (mappedHandler != null ? mappedHandler.getHandler() : null);
mv = processHandlerException(request, response, handler, exception);
errorView = (mv != null);
}
}
// Did the handler return a view to render?
if (mv != null && !mv.wasCleared()) {
// 渲染视图！！！参考（12）
render(mv, request, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
}
else {
if (logger.isDebugEnabled()) {
logger.debug("Null ModelAndView returned to DispatcherServlet with name '" + getServletName() +
"': assuming HandlerAdapter completed request handling");
}
}
if (WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {
// Concurrent handling started during a forward
return;
}
if (mappedHandler != null) {
//执行拦截器的afterCompletion方法 参考（13）
mappedHandler.triggerAfterCompletion(request, response, null);
}
}
(12).DispatcherServlet.render()
源码如下：
protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception {
// Determine locale for request and apply it to the response.
//本例这里为zh_CN
Locale locale =
(this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale());
//为响应设置Locale对象
response.setLocale(locale);
View view;
String viewName = mv.getViewName();
if (viewName != null) {
// We need to resolve the view name.
//根据视图解析器获取View对象
view = resolveViewName(viewName, mv.getModelInternal(), locale, request);
if (view == null) {
throw new ServletException("Could not resolve view with name '" + mv.getViewName() +
"' in servlet with name '" + getServletName() + "'");
}
}
else {
// No need to lookup: the ModelAndView object contains the actual View object.
view = mv.getView();
if (view == null) {
throw new ServletException("ModelAndView [" + mv + "] neither contains a view name nor a " +
"View object in servlet with name '" + getServletName() + "'");
}
}
// Delegate to the View object for rendering.
if (logger.isDebugEnabled()) {
logger.debug("Rendering view [" + view + "] in DispatcherServlet with name '" + getServletName() + "'");
}
try {
if (mv.getStatus() != null) {
response.setStatus(mv.getStatus().value());
}
/*Render the view given the specified model.
The first step will be preparing the request: In the JSP case,this would mean setting model objects as request attributes.
The second step will be the actual rendering of the view,for example including the JSP via a RequestDispatcher.
*/
view.render(mv.getModelInternal(), request, response);
}
catch (Exception ex) {
if (logger.isDebugEnabled()) {
logger.debug("Error rendering view [" + view + "] in DispatcherServlet with name '" +
getServletName() + "'", ex);
}
throw ex;
}
}
(13)HandlerExecutionChain.triggerAfterCompletion
源码如下：
void triggerAfterCompletion(HttpServletRequest request, HttpServletResponse response, @Nullable Exception ex)
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = this.interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
try {
interceptor.afterCompletion(request, response, this.handler, ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
}
程序依次返回，直到第⑤中的publishRequestHandledEvent！
(14)FrameworkServlet.publishRequestHandledEvent
源码如下：
private void publishRequestHandledEvent(HttpServletRequest request, HttpServletResponse response,
long startTime, @Nullable Throwable failureCause) {
if (this.publishEvents && this.webApplicationContext != null) {
// Whether or not we succeeded, publish an event.
long processingTime = System.currentTimeMillis() - startTime;
this.webApplicationContext.publishEvent(
new ServletRequestHandledEvent(this,
request.getRequestURI(), request.getRemoteAddr(),
request.getMethod(), getServletConfig().getServletName(),
WebUtils.getSessionId(request), getUsernameForRequest(request),
processingTime, failureCause, response.getStatus()));
}
}
其调用了webApplicationContext.publishEvent！是不是很熟悉？
【5】@ResponseBody注解返回JSON
即，方法返回json，不再是视图，此时该如何？
此时(10.5)中改变RequestResponseBodyMethodProcessor.handleReturnValue():
@Override
public void handleReturnValue(@Nullable Object returnValue, MethodParameter returnType,
ModelAndViewContainer mavContainer, NativeWebRequest webRequest)
throws IOException, HttpMediaTypeNotAcceptableException, HttpMessageNotWritableException {
mavContainer.setRequestHandled(true);
ServletServerHttpRequest inputMessage = createInputMessage(webRequest);
ServletServerHttpResponse outputMessage = createOutputMessage(webRequest);
// Try even with null return value. ResponseBodyAdvice could get involved.
writeWithMessageConverters(returnValue, returnType, inputMessage, outputMessage);
}