本笔记基于springBoot 2.3.3版本
基本知识
到目前为止Servlet规范已经发展到Servlet3.0/4.0阶段，在Servlet 3.0阶段 允许开发人员采用注解的方式来配置 Servlet、Filter、Listener。这个是springboot集成springmvc的一个重要基础。
servlet规范(实际我们工程中引入的是javax.servlet-api:3.0.1 这个jar包，后面我们会用jar包来称呼比较好理解) ，我们知道servlet jar包里的Servlet接口最重要的三个方法是：init service destroy（当然里面还有其他方法）
其中init在在服务初始化阶段调用，service在服务运行中调用，destroy方法在服务销毁时调用。这个是基础流程，那这三个阶段在springmvc框架中是如何运行的，或者说springmvc如何实现这三个阶段。
工程启动过程中会有三个ApplicationContext对象：https://blog.youkuaiyun.com/qq_42239765/article/details/106007967
1、tomcat ApplicationContext（继承于servletContext对象），
2、spring应用上下文对象AnnotationConfigServletWebServerApplicationContext（继承实现于ApplicationContext这个和前一个是不同jar包里的类，别弄错了）
3、springmvc应用上下文XmlWebApplicationContext（同样继承实现于ApplicationContext）
spring的应用上下文是springmvc上下文的parent。
spring和springmvc的上下文都通过固定属性名保存在tomcat ApplicationContext当中。
tomcat知识
springboot在jar包模式下采用了内嵌tomcat服务器来实现，所以就main开始看源码。
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}所有的springboot工程都是从如上代码开始的，我们就从这里开始。跟着run方法一路来到下图方法
从refreshContext方法一路到下图：
onRefresh方法是初始化tomcat和mvc重要方法：继续往下
进入到createWebServer方法里面
getSelfInitializer这个方法用了lamad表达式返回了ServletContextInitializer对象（onStartup方法里面执行selfInitialize方法)这个实例对象很重要，后面会再次用到，先记着。
private org.springframework.boot.web.servlet.ServletContextInitializer getSelfInitializer() {
return this::selfInitialize;
}
private void selfInitialize(ServletContext servletContext) throws ServletException {
****prepareWebApplicationContext(servletContext);
registerApplicationScope(servletContext);
WebApplicationContextUtils.registerEnvironmentBeans(getBeanFactory(), servletContext);
****for (ServletContextInitializer beans : getServletContextInitializerBeans()) {
*****beans.onStartup(servletContext);
}
}getWebServer(getSelfInitializer())里面进行了tomcat及子容器的初始化。如下
@Override
public WebServer getWebServer(ServletContextInitializer... initializers) {
if (this.disableMBeanRegistry) {
Registry.disableRegistry();
}
*******Tomcat tomcat = new Tomcat();
File baseDir = (this.baseDirectory != null) ? this.baseDirectory : createTempDir("tomcat");
tomcat.setBaseDir(baseDir.getAbsolutePath());
Connector connector = new Connector(this.protocol);
connector.setThrowOnFailure(true);
****tomcat.getService().addConnector(connector);
customizeConnector(connector);
tomcat.setConnector(connector);
*****tomcat.getHost().setAutoDeploy(false);
configureEngine(tomcat.getEngine());
for (Connector additionalConnector : this.additionalTomcatConnectors) {
tomcat.getService().addConnector(additionalConnector);
}
*****prepareContext(tomcat.getHost(), initializers);
return ******getTomcatWebServer(tomcat);
}tomcat层级分为：server-> service -> engine -> host - >context - >wrapper 。其中engine以后都属于容器其中都包括child属性
getWebServer方法中对server service engine host都进行了默认实现分别是StandardServer，StandardService，StandardEngine，StandardHost，
prepareContext方法里面用TomcatEmbeddedContext（继承于StandardContext）对host的下级child进行了填充，同时如下图：
protected void prepareContext(Host host, ServletContextInitializer[] initializers) {
File documentRoot = getValidDocumentRoot();
******TomcatEmbeddedContext context = new TomcatEmbeddedContext();
if (documentRoot != null) {
context.setResources(new LoaderHidingResourceRoot(context));
}
context.setName(getContextPath());
context.setDisplayName(getDisplayName());
context.setPath(getContextPath());
File docBase = (documentRoot != null) ? documentRoot : createTempDir("tomcat-docbase");
context.setDocBase(docBase.getAbsolutePath());
context.addLifecycleListener(new FixContextListener());
context.setParentClassLoader((this.resourceLoader != null) ? this.resourceLoader.getClassLoader()
: ClassUtils.getDefaultClassLoader());
resetDefaultLocaleMapping(context);
addLocaleMappings(context);
try {
context.setCreateUploadTargets(true);
}
catch (NoSuchMethodError ex) {
// Tomcat is < 8.5.39. Continue.
}
configureTldSkipPatterns(context);
WebappLoader loader = new WebappLoader();
loader.setLoaderClass(TomcatEmbeddedWebappClassLoader.class.getName());
loader.setDelegate(true);
context.setLoader(loader);
if (isRegisterDefaultServlet()) {
addDefaultServlet(context);
}
if (shouldRegisterJspServlet()) {
addJspServlet(context);
addJasperInitializer(context);
}
context.addLifecycleListener(new StaticResourceConfigurer(context));
ServletContextInitializer[] initializersToUse = mergeInitializers(initializers);
******host.addChild(context);
******configureContext(context, initializersToUse);
postProcessContext(context);
}configureContext用getSelfInitializer生成的ServletContextInitializer 创建对象TomcatStarter ，然后将其添加到TomcatEmbeddedContext当中
protected void configureContext(Context context, ServletContextInitializer[] initializers) {
TomcatStarter starter = new TomcatStarter(initializers);
if (context instanceof TomcatEmbeddedContext) {
TomcatEmbeddedContext embeddedContext = (TomcatEmbeddedContext) context;
embeddedContext.setStarter(starter);
embeddedContext.setFailCtxIfServletStartFails(true);
}
****** context.addServletContainerInitializer(starter, NO_CLASSES);
for (LifecycleListener lifecycleListener : this.contextLifecycleListeners) {
context.addLifecycleListener(lifecycleListener);
}
for (Valve valve : this.contextValves) {
context.getPipeline().addValve(valve);
}
for (ErrorPage errorPage : getErrorPages()) {
org.apache.tomcat.util.descriptor.web.ErrorPage tomcatErrorPage = new org.apache.tomcat.util.descriptor.web.ErrorPage();
tomcatErrorPage.setLocation(errorPage.getPath());
tomcatErrorPage.setErrorCode(errorPage.getStatusCode());
tomcatErrorPage.setExceptionType(errorPage.getExceptionName());
context.addErrorPage(tomcatErrorPage);
}
for (MimeMappings.Mapping mapping : getMimeMappings()) {
context.addMimeMapping(mapping.getExtension(), mapping.getMimeType());
}
configureSession(context);
new DisableReferenceClearingContextCustomizer().customize(context);
for (TomcatContextCustomizer customizer : this.tomcatContextCustomizers) {
customizer.customize(context);
}
}如下图getTomcatWebServer方法正式开启了tomcat各级容器的初始化工作。从Standarderver的start()方法开始。
protected TomcatWebServer getTomcatWebServer(Tomcat tomcat) {
return new TomcatWebServer(tomcat, getPort() >= 0, getShutdown());
}
public TomcatWebServer(Tomcat tomcat, boolean autoStart, Shutdown shutdown) {
Assert.notNull(tomcat, "Tomcat Server must not be null");
this.tomcat = tomcat;
this.autoStart = autoStart;
this.gracefulShutdown = (shutdown == Shutdown.GRACEFUL) ? new GracefulShutdown(tomcat) : null;
********initialize();
}
private void initialize() throws WebServerException {
logger.info("Tomcat initialized with port(s): " + getPortsDescription(false));
synchronized (this.monitor) {
try {
addInstanceIdToEngineName();
Context context = findContext();
context.addLifecycleListener((event) -> {
if (context.equals(event.getSource()) && Lifecycle.START_EVENT.equals(event.getType())) {
// Remove service connectors so that protocol binding doesn't
// happen when the service is started.
removeServiceConnectors();
}
});
// Start the server to trigger initialization listeners
***********this.tomcat.start();
// We can re-throw failure exception directly in the main thread
rethrowDeferredStartupExceptions();
try {
ContextBindings.bindClassLoader(context, context.getNamingToken(), getClass().getClassLoader());
}
catch (NamingException ex) {
// Naming is not enabled. Continue
}
// Unlike Jetty, all Tomcat threads are daemon threads. We create a
// blocking non-daemon to stop immediate shutdown
startDaemonAwaitThread();
}
catch (Exception ex) {
stopSilently();
destroySilently();
throw new WebServerException("Unable to start embedded Tomcat", ex);
}
}
}整个流程比较长先执行各级 init 方法，然后再执行startInternal 方法，具体时序图见 https://blog.youkuaiyun.com/caoyuanyenang/article/details/114366907
@Override
public final synchronized void start() throws LifecycleException {
if (LifecycleState.STARTING_PREP.equals(state) || LifecycleState.STARTING.equals(state) ||
LifecycleState.STARTED.equals(state)) {
if (log.isDebugEnabled()) {
Exception e = new LifecycleException();
log.debug(sm.getString("lifecycleBase.alreadyStarted", toString()), e);
} else if (log.isInfoEnabled()) {
log.info(sm.getString("lifecycleBase.alreadyStarted", toString()));
}
return;
}
if (state.equals(LifecycleState.NEW)) {
**** init();
} else if (state.equals(LifecycleState.FAILED)) {
stop();
} else if (!state.equals(LifecycleState.INITIALIZED) &&
!state.equals(LifecycleState.STOPPED)) {
invalidTransition(Lifecycle.BEFORE_START_EVENT);
}
try {
setStateInternal(LifecycleState.STARTING_PREP, null, false);
**** startInternal();
if (state.equals(LifecycleState.FAILED)) {
// This is a 'controlled' failure. The component put itself into the
// FAILED state so call stop() to complete the clean-up.
stop();
} else if (!state.equals(LifecycleState.STARTING)) {
// Shouldn't be necessary but acts as a check that sub-classes are
// doing what they are supposed to.
invalidTransition(Lifecycle.AFTER_START_EVENT);
} else {
setStateInternal(LifecycleState.STARTED, null, false);
}
} catch (Throwable t) {
// This is an 'uncontrolled' failure so put the component into the
// FAILED state and throw an exception.
handleSubClassException(t, "lifecycleBase.startFail", toString());
}
}
最后会来到TomcatEmbeddedContext（StandardContext）类的startInternal 方法。这里面主要有如下几个方法。
postWorkDirectory 这个方法主要是初始化tomcat的ApplicationContext对象并会生成门面对象ApplicationContextFacade。
entry.getKey().onStartup(entry.getValue(),getServletContext()); 这个方法会调TomcatStarter方法onStartup方法，最终会调用到getSelfInitializer生成的对象方法selfInitialize。selfInitialize将spring应用上下文设置为tomcat应用上下文的一个属性，并从spring应用上下文中找出ServletContextInitializer类型对象，执行其onStartup方法。DispatcherServlet， filter, lister这几种都是通过继承ServletContextInitializer来实现添加进tomcat应用上下文的。在添加DispatcherServlet的同时，也会生成standardWrapper并放入standardContext。如下图：
@Override
protected synchronized void startInternal() throws LifecycleException {
if(log.isDebugEnabled())
log.debug("Starting " + getBaseName());
// Send j2ee.state.starting notification
if (this.getObjectName() != null) {
Notification notification = new Notification("j2ee.state.starting",
this.getObjectName(), sequenceNumber.getAndIncrement());
broadcaster.sendNotification(notification);
}
setConfigured(false);
boolean ok = true;
// Currently this is effectively a NO-OP but needs to be called to
// ensure the NamingResources follows the correct lifecycle
if (namingResources != null) {
namingResources.start();
}
// Post work directory
************ postWorkDirectory();
// Add missing components as necessary
if (getResources() == null) { // (1) Required by Loader
if (log.isDebugEnabled())
log.debug("Configuring default Resources");
try {
setResources(new StandardRoot(this));
} catch (IllegalArgumentException e) {
log.error(sm.getString("standardContext.resourcesInit"), e);
ok = false;
}
}
if (ok) {
resourcesStart();
}
if (getLoader() == null) {
WebappLoader webappLoader = new WebappLoader();
webappLoader.setDelegate(getDelegate());
setLoader(webappLoader);
}
// An explicit cookie processor hasn't been specified; use the default
if (cookieProcessor == null) {
cookieProcessor = new Rfc6265CookieProcessor();
}
// Initialize character set mapper
getCharsetMapper();
// Validate required extensions
boolean dependencyCheck = true;
try {
dependencyCheck = ExtensionValidator.validateApplication
(getResources(), this);
} catch (IOException ioe) {
log.error(sm.getString("standardContext.extensionValidationError"), ioe);
dependencyCheck = false;
}
if (!dependencyCheck) {
// do not make application available if dependency check fails
ok = false;
}
// Reading the "catalina.useNaming" environment variable
String useNamingProperty = System.getProperty("catalina.useNaming");
if ((useNamingProperty != null)
&& (useNamingProperty.equals("false"))) {
useNaming = false;
}
if (ok && isUseNaming()) {
if (getNamingContextListener() == null) {
NamingContextListener ncl = new NamingContextListener();
ncl.setName(getNamingContextName());
ncl.setExceptionOnFailedWrite(getJndiExceptionOnFailedWrite());
addLifecycleListener(ncl);
setNamingContextListener(ncl);
}
}
// Standard container startup
if (log.isDebugEnabled())
log.debug("Processing standard container startup");
// Binding thread
ClassLoader oldCCL = bindThread();
try {
if (ok) {
// Start our subordinate components, if any
Loader loader = getLoader();
if (loader instanceof Lifecycle) {
((Lifecycle) loader).start();
}
// since the loader just started, the webapp classloader is now
// created.
setClassLoaderProperty("clearReferencesRmiTargets",
getClearReferencesRmiTargets());
setClassLoaderProperty("clearReferencesStopThreads",
getClearReferencesStopThreads());
setClassLoaderProperty("clearReferencesStopTimerThreads",
getClearReferencesStopTimerThreads());
setClassLoaderProperty("clearReferencesHttpClientKeepAliveThread",
getClearReferencesHttpClientKeepAliveThread());
setClassLoaderProperty("clearReferencesObjectStreamClassCaches",
getClearReferencesObjectStreamClassCaches());
setClassLoaderProperty("clearReferencesObjectStreamClassCaches",
getClearReferencesObjectStreamClassCaches());
setClassLoaderProperty("clearReferencesThreadLocals",
getClearReferencesThreadLocals());
// By calling unbindThread and bindThread in a row, we setup the
// current Thread CCL to be the webapp classloader
unbindThread(oldCCL);
oldCCL = bindThread();
// Initialize logger again. Other components might have used it
// too early, so it should be reset.
logger = null;
getLogger();
Realm realm = getRealmInternal();
if(null != realm) {
if (realm instanceof Lifecycle) {
((Lifecycle) realm).start();
}
// Place the CredentialHandler into the ServletContext so
// applications can have access to it. Wrap it in a "safe"
// handler so application's can't modify it.
CredentialHandler safeHandler = new CredentialHandler() {
@Override
public boolean matches(String inputCredentials, String storedCredentials) {
return getRealmInternal().getCredentialHandler().matches(inputCredentials, storedCredentials);
}
@Override
public String mutate(String inputCredentials) {
return getRealmInternal().getCredentialHandler().mutate(inputCredentials);
}
};
context.setAttribute(Globals.CREDENTIAL_HANDLER, safeHandler);
}
// Notify our interested LifecycleListeners
fireLifecycleEvent(Lifecycle.CONFIGURE_START_EVENT, null);
// Start our child containers, if not already started
for (Container child : findChildren()) {
if (!child.getState().isAvailable()) {
child.start();
}
}
// Start the Valves in our pipeline (including the basic),
// if any
if (pipeline instanceof Lifecycle) {
((Lifecycle) pipeline).start();
}
// Acquire clustered manager
Manager contextManager = null;
Manager manager = getManager();
if (manager == null) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("standardContext.cluster.noManager",
Boolean.valueOf((getCluster() != null)),
Boolean.valueOf(distributable)));
}
if ((getCluster() != null) && distributable) {
try {
contextManager = getCluster().createManager(getName());
} catch (Exception ex) {
log.error(sm.getString("standardContext.cluster.managerError"), ex);
ok = false;
}
} else {
contextManager = new StandardManager();
}
}
// Configure default manager if none was specified
if (contextManager != null) {
if (log.isDebugEnabled()) {
log.debug(sm.getString("standardContext.manager",
contextManager.getClass().getName()));
}
setManager(contextManager);
}
if (manager!=null && (getCluster() != null) && distributable) {
//let the cluster know that there is a context that is distributable
//and that it has its own manager
getCluster().registerManager(manager);
}
}
if (!getConfigured()) {
log.error(sm.getString("standardContext.configurationFail"));
ok = false;
}
// We put the resources into the servlet context
if (ok) {
getServletContext().setAttribute
(Globals.RESOURCES_ATTR, getResources());
if (getInstanceManager() == null) {
setInstanceManager(createInstanceManager());
}
getServletContext().setAttribute(
InstanceManager.class.getName(), getInstanceManager());
InstanceManagerBindings.bind(getLoader().getClassLoader(), getInstanceManager());
// Create context attributes that will be required
getServletContext().setAttribute(
JarScanner.class.getName(), getJarScanner());
// Make the version info available
getServletContext().setAttribute(Globals.WEBAPP_VERSION, getWebappVersion());
}
// Set up the context init params
mergeParameters();
// Call ServletContainerInitializers
for (Map.Entry<ServletContainerInitializer, Set<Class<?>>> entry :
initializers.entrySet()) {
try {
******** entry.getKey().onStartup(entry.getValue(),
getServletContext());
} catch (ServletException e) {
log.error(sm.getString("standardContext.sciFail"), e);
ok = false;
break;
}
}
// Configure and call application event listeners
if (ok) {
if (!listenerStart()) {
log.error(sm.getString("standardContext.listenerFail"));
ok = false;
}
}
// Check constraints for uncovered HTTP methods
// Needs to be after SCIs and listeners as they may programmatically
// change constraints
if (ok) {
checkConstraintsForUncoveredMethods(findConstraints());
}
try {
// Start manager
Manager manager = getManager();
if (manager instanceof Lifecycle) {
((Lifecycle) manager).start();
}
} catch(Exception e) {
log.error(sm.getString("standardContext.managerFail"), e);
ok = false;
}
// Configure and call application filters
if (ok) {
if (!filterStart()) {
log.error(sm.getString("standardContext.filterFail"));
ok = false;
}
}
// Load and initialize all "load on startup" servlets
if (ok) {
if (!loadOnStartup(findChildren())){
log.error(sm.getString("standardContext.servletFail"));
ok = false;
}
}
// Start ContainerBackgroundProcessor thread
super.threadStart();
} finally {
// Unbinding thread
unbindThread(oldCCL);
}
// Set available status depending upon startup success
if (ok) {
if (log.isDebugEnabled())
log.debug("Starting completed");
} else {
log.error(sm.getString("standardContext.startFailed", getName()));
}
startTime=System.currentTimeMillis();
// Send j2ee.state.running notification
if (ok && (this.getObjectName() != null)) {
Notification notification =
new Notification("j2ee.state.running", this.getObjectName(),
sequenceNumber.getAndIncrement());
broadcaster.sendNotification(notification);
}
// The WebResources implementation caches references to JAR files. On
// some platforms these references may lock the JAR files. Since web
// application start is likely to have read from lots of JARs, trigger
// a clean-up now.
getResources().gc();
// Reinitializing if something went wrong
if (!ok) {
setState(LifecycleState.FAILED);
// Send j2ee.object.failed notification
if (this.getObjectName() != null) {
Notification notification = new Notification("j2ee.object.failed",
this.getObjectName(), sequenceNumber.getAndIncrement());
broadcaster.sendNotification(notification);
}
} else {
setState(LifecycleState.STARTING);
}
}getWebServer 方法之后是getBeanFactory().registerSingleton("webServerStartStop",new WebServerStartStopLifecycle(this, this.webServer)); 至此mvc完成了初始化的准备工作。 其初始化正式开始于finishRefresh();如下图从这里开始才是servlet init方法正式开始之处。
protected void finishRefresh() {
// Clear context-level resource caches (such as ASM metadata from scanning).
clearResourceCaches();
// Initialize lifecycle processor for this context.
******initLifecycleProcessor();
// Propagate refresh to lifecycle processor first.
******getLifecycleProcessor().onRefresh();
// Publish the final event.
publishEvent(new ContextRefreshedEvent(this));
// Participate in LiveBeansView MBean, if active.
LiveBeansView.registerApplicationContext(this);
}从getLifecycleProcessor().onRefresh()-> DefaultLifecycleProcessor.onRefresh->DefaultLifecycleProcessor.startBeans->LifecycleGroup.start->WebServerStartStopLifecycle.start->TomcatWebServer.start->
TomcatWebServer.performDeferredLoadOnStartup->TomcatEmbeddedContext.deferredLoadOnStartup->TomcatEmbeddedContext.load->StandardWrapper.load->StandardWrapper.loadServlet->StandardWrapper.initServlet
至此终于到了DispatcherServlet类的init方法了，接下来分析其init方法。
GenericServlet.init->HttpServletBean.init->FrameworkServlet.initServletBean->FrameworkServlet.initWebApplicationContext(这个方法里对springmvc应用上下文进行了初始化，并将spring应用上下文作为其parent)->DispatcherServlet.onRefresh
->DispatcherServlet.initStrategies(这个方法里面会对handlerMappings和handlerAdapters等做初始化， dispatcherServlet 里目前用的是RequestMappingHandlerMapping handlerMapping。
该类会通过WebMvcAutoConfiguration自动装配进入spring应用上下文。)。
至此DispatcherServletinit方法完毕，接下来就是DispatcherServlet service方法分析了。
请求进来->HttpServlet.service(ServletRequest req, ServletResponse res)->HttpServlet.service(HttpServletRequest req, HttpServletResponse resp)->HttpServlet-doGet->FrameworkServlet.doGet-> FrameworkServlet.processRequest
->DispatcherServlet.doService->DispatcherServlet.doDispatch doDispatch方法里面有几个重要的点：如下图：
1. 这个方法是要通过请求url获取响应的处理链（主要是从找RequestMappingHandlerMapping 里找 controller方法。）
2.该方法找到handlerMapping响应的适配器，解决兼容问题
3.找出并执行该方法适配的前置拦截器方法（
拦截器是通过WebMvcConfigurer添加入springmvc应用上下文，然后DelegatingWebMvcConfiguration将所有的WebMvcConfigurer注入，并添加进RequestMappingHandlerMapping 里面。requestMappingHandlerMapping通过WebMvcAutoConfiguration @bean注入-》WebMvcConfigurationSupport @bean 注入。然后通过getInterceptors方法获取所有拦截器并设置。）
4.执行找到的controller里的方法
5.找出并执行该方法适配的后置拦截器方法
6.对结果进行处理（包括解析和渲染视图）ModelAndView
protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {
HttpServletRequest processedRequest = request;
HandlerExecutionChain mappedHandler = null;
boolean multipartRequestParsed = false;
WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);
try {
ModelAndView mv = null;
Exception dispatchException = null;
try {
processedRequest = checkMultipart(request);
multipartRequestParsed = (processedRequest != request);
// Determine handler for the current request.
1. mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
2.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 (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) {
return;
}
}
3. if (!mappedHandler.applyPreHandle(processedRequest, response)) {
return;
}
// Actually invoke the handler.
4. mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
5. 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);
}
6. 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);
}
}
}
}https://www.cnblogs.com/zktww/p/11550891.html
https://blog.51cto.com/u_15009303/2552937
https://www.cnblogs.com/guoxiaoyu/archive/2020/07/31/13402861.html
https://blog.youkuaiyun.com/u013378306/article/details/106963152
https://segmentfault.com/a/1190000022763768
https://blog.youkuaiyun.com/caoyuanyenang/article/details/114366907
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