前言
本文主要讲的是，自定义了一个拦截器，然后流程是什么样的。
核心流程
先获取所有拦截器
先是项目启动成功，然后浏览器请求，就会走到这里来，获取所有拦截器。
拦截器数据存储在拦截器链类的集合里。
再执行自定义拦截器
再走到自定义拦截器来
其实每个拦截器都会执行，即拦截器链里的每个拦截器都会执行，截图里的是执行到了自定义拦截器。
方法调用栈
preHandle:21, LoggerInterceptor (sample.tomcat.intecepter) //自定义拦截器的方法
applyPreHandle:136, HandlerExecutionChain (org.springframework.web.servlet)
doDispatch:1033, DispatcherServlet (org.springframework.web.servlet) //mvc的核心类的核心方法
doService:942, DispatcherServlet
(org.springframework.web.servlet)
processRequest:1005, FrameworkServlet (org.springframework.web.servlet)
doGet:897, FrameworkServlet (org.springframework.web.servlet)
service:634, HttpServlet (javax.servlet.http)
service:882, FrameworkServlet (org.springframework.web.servlet)
service:741, HttpServlet (javax.servlet.http)
internalDoFilter:231, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilter:53, WsFilter (org.apache.tomcat.websocket.server)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:99, RequestContextFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:92, FormContentFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:93, HiddenHttpMethodFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:200, CharacterEncodingFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
invoke:200, StandardWrapperValve (org.apache.catalina.core)
invoke:96, StandardContextValve (org.apache.catalina.core)
invoke:490, AuthenticatorBase (org.apache.catalina.authenticator)
invoke:139, StandardHostValve (org.apache.catalina.core)
invoke:92, ErrorReportValve (org.apache.catalina.valves)
invoke:74, StandardEngineValve (org.apache.catalina.core)
service:343, CoyoteAdapter (org.apache.catalina.connector)
service:408, Http11Processor (org.apache.coyote.http11)
process:66, AbstractProcessorLight (org.apache.coyote)
process:834, AbstractProtocol$ConnectionHandler (org.apache.coyote)
doRun:1415, NioEndpoint$SocketProcessor (org.apache.tomcat.util.net)
run:49, SocketProcessorBase (org.apache.tomcat.util.net)
runWorker:1128, ThreadPoolExecutor (java.util.concurrent)
run:628, ThreadPoolExecutor$Worker (java.util.concurrent)
run:61, TaskThread$WrappingRunnable (org.apache.tomcat.util.threads)
run:834, Thread (java.lang)
源码分析
核心类DispatcherServlet
在DispatcherServlet的doDispatch方法，核心流程是
1.执行每个拦截器的前置方法
2.执行业务类的业务方法
3.执行每个拦截器的后置方法
/**
* Central dispatcher for HTTP request handlers/controllers, e.g. for web UI controllers
* or HTTP-based remote service exporters. Dispatches to registered handlers for processing
* a web request, providing convenient mapping and exception handling facilities.
*
* <p>This servlet is very flexible: It can be used with just about any workflow, with the
* installation of the appropriate adapter classes. It offers the following functionality
* that distinguishes it from other request-driven web MVC frameworks:
*
* <ul>
* <li>It is based around a JavaBeans configuration mechanism.
*
* <li>It can use any {@link HandlerMapping} implementation - pre-built or provided as part
* of an application - to control the routing of requests to handler objects. Default is
* {@link org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping} and
* {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping}.
* HandlerMapping objects can be defined as beans in the servlet's application context,
* implementing the HandlerMapping interface, overriding the default HandlerMapping if
* present. HandlerMappings can be given any bean name (they are tested by type).
*
* <li>It can use any {@link HandlerAdapter}; this allows for using any handler interface.
* Default adapters are {@link org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter},
* {@link org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter}, for Spring's
* {@link org.springframework.web.HttpRequestHandler} and
* {@link org.springframework.web.servlet.mvc.Controller} interfaces, respectively. A default
* {@link org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter}
* will be registered as well. HandlerAdapter objects can be added as beans in the
* application context, overriding the default HandlerAdapters. Like HandlerMappings,
* HandlerAdapters can be given any bean name (they are tested by type).
*
* <li>The dispatcher's exception resolution strategy can be specified via a
* {@link HandlerExceptionResolver}, for example mapping certain exceptions to error pages.
* Default are
* {@link org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver},
* {@link org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver}, and
* {@link org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver}.
* These HandlerExceptionResolvers can be overridden through the application context.
* HandlerExceptionResolver can be given any bean name (they are tested by type).
*
* <li>Its view resolution strategy can be specified via a {@link ViewResolver}
* implementation, resolving symbolic view names into View objects. Default is
* {@link org.springframework.web.servlet.view.InternalResourceViewResolver}.
* ViewResolver objects can be added as beans in the application context, overriding the
* default ViewResolver. ViewResolvers can be given any bean name (they are tested by type).
*
* <li>If a {@link View} or view name is not supplied by the user, then the configured
* {@link RequestToViewNameTranslator} will translate the current request into a view name.
* The corresponding bean name is "viewNameTranslator"; the default is
* {@link org.springframework.web.servlet.view.DefaultRequestToViewNameTranslator}.
*
* <li>The dispatcher's strategy for resolving multipart requests is determined by a
* {@link org.springframework.web.multipart.MultipartResolver} implementation.
* Implementations for Apache Commons FileUpload and Servlet 3 are included; the typical
* choice is {@link org.springframework.web.multipart.commons.CommonsMultipartResolver}.
* The MultipartResolver bean name is "multipartResolver"; default is none.
*
* <li>Its locale resolution strategy is determined by a {@link LocaleResolver}.
* Out-of-the-box implementations work via HTTP accept header, cookie, or session.
* The LocaleResolver bean name is "localeResolver"; default is
* {@link org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver}.
*
* <li>Its theme resolution strategy is determined by a {@link ThemeResolver}.
* Implementations for a fixed theme and for cookie and session storage are included.
* The ThemeResolver bean name is "themeResolver"; default is
* {@link org.springframework.web.servlet.theme.FixedThemeResolver}.
* </ul>
*
* <p><b>NOTE: The {@code @RequestMapping} annotation will only be processed if a
* corresponding {@code HandlerMapping} (for type-level annotations) and/or
* {@code HandlerAdapter} (for method-level annotations) is present in the dispatcher.</b>
* This is the case by default. However, if you are defining custom {@code HandlerMappings}
* or {@code HandlerAdapters}, then you need to make sure that a corresponding custom
* {@code RequestMappingHandlerMapping} and/or {@code RequestMappingHandlerAdapter}
* is defined as well - provided that you intend to use {@code @RequestMapping}.
*
* <p><b>A web application can define any number of DispatcherServlets.</b>
* Each servlet will operate in its own namespace, loading its own application context
* with mappings, handlers, etc. Only the root application context as loaded by
* {@link org.springframework.web.context.ContextLoaderListener}, if any, will be shared.
*
* <p>As of Spring 3.1, {@code DispatcherServlet} may now be injected with a web
* application context, rather than creating its own internally. This is useful in Servlet
* 3.0+ environments, which support programmatic registration of servlet instances.
* See the {@link #DispatcherServlet(WebApplicationContext)} javadoc for details.
*
* @author Rod Johnson
* @author Juergen Hoeller
* @author Rob Harrop
* @author Chris Beams
* @author Rossen Stoyanchev
* @see org.springframework.web.HttpRequestHandler
* @see org.springframework.web.servlet.mvc.Controller
* @see org.springframework.web.context.ContextLoaderListener
*/
@SuppressWarnings("serial")
public class DispatcherServlet extends FrameworkServlet {
/**
* 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;
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.
mappedHandler = getHandler(processedRequest);
if (mappedHandler == null) {
noHandlerFound(processedRequest, response);
return;
}
// Determine handler adapter for the current request.
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;
}
}
if (!mappedHandler.applyPreHandle(processedRequest, response)) { //执行每个拦截器的前置方法
return;
}
// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); //执行业务类的业务方法
if (asyncManager.isConcurrentHandlingStarted()) {
return;
}
applyDefaultViewName(processedRequest, mv);
mappedHandler.applyPostHandle(processedRequest, response, mv); //执行每个拦截器的后置方法
}
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);
}
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);
}
}
}
}
拦截器链HandlerExecutionChain
执行前置方法
进入到拦截器链之后，循环执行所有拦截器的前置方法。
/**
* Handler execution chain, consisting of handler object and any handler interceptors.
* Returned by HandlerMapping's {@link HandlerMapping#getHandler} method.
*
* @author Juergen Hoeller
* @since 20.06.2003
* @see HandlerInterceptor
*/
public class HandlerExecutionChain {
/**
* Apply preHandle methods of registered interceptors.
* @return {@code true} if the execution chain should proceed with the
* next interceptor or the handler itself. Else, DispatcherServlet assumes
* that this interceptor has already dealt with the response itself.
*/
boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = 0; i < interceptors.length; i++) { //循环执行拦截器
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(request, response, this.handler)) { //执行拦截器的前置方法。这个时候只是执行前置方法。
triggerAfterCompletion(request, response, null);
return false;
}
this.interceptorIndex = i;
}
}
return true;
}
执行后置方法
执行每个拦截器的后置方法
/**
* Apply postHandle methods of registered interceptors.
*/
void applyPostHandle(HttpServletRequest request, HttpServletResponse response, @Nullable ModelAndView mv) //执行拦截器的后置方法
throws Exception {
HandlerInterceptor[] interceptors = getInterceptors();
if (!ObjectUtils.isEmpty(interceptors)) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(request, response, this.handler, mv); //循环执行每个拦截器的后置方法
}
}
}
方法调用栈，前置方法的方法调用栈也类似。
postHandle:27, LoggerInterceptor (sample.tomcat.intecepter) //执行自定义拦截器的后置方法
applyPostHandle:156, HandlerExecutionChain (org.springframework.web.servlet) //执行每个拦截器的后置方法
doDispatch:1045, DispatcherServlet (org.springframework.web.servlet) //核心类的核心方法
doService:942, DispatcherServlet (org.springframework.web.servlet)
processRequest:1005, FrameworkServlet (org.springframework.web.servlet)
doGet:897, FrameworkServlet (org.springframework.web.servlet)
service:634, HttpServlet (javax.servlet.http)
service:882, FrameworkServlet (org.springframework.web.servlet)
service:741, HttpServlet (javax.servlet.http)
internalDoFilter:231, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilter:53, WsFilter (org.apache.tomcat.websocket.server)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:99, RequestContextFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:92, FormContentFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:93, HiddenHttpMethodFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
doFilterInternal:200, CharacterEncodingFilter (org.springframework.web.filter)
doFilter:107, OncePerRequestFilter (org.springframework.web.filter)
internalDoFilter:193, ApplicationFilterChain (org.apache.catalina.core)
doFilter:166, ApplicationFilterChain (org.apache.catalina.core)
invoke:200, StandardWrapperValve (org.apache.catalina.core)
invoke:96, StandardContextValve (org.apache.catalina.core)
invoke:490, AuthenticatorBase (org.apache.catalina.authenticator)
invoke:139, StandardHostValve (org.apache.catalina.core)
invoke:92, ErrorReportValve (org.apache.catalina.valves)
invoke:74, StandardEngineValve (org.apache.catalina.core)
service:343, CoyoteAdapter (org.apache.catalina.connector)
service:408, Http11Processor (org.apache.coyote.http11)
process:66, AbstractProcessorLight (org.apache.coyote)
process:834, AbstractProtocol$ConnectionHandler (org.apache.coyote)
doRun:1415, NioEndpoint$SocketProcessor (org.apache.tomcat.util.net)
run:49, SocketProcessorBase (org.apache.tomcat.util.net)
runWorker:1128, ThreadPoolExecutor (java.util.concurrent)
run:628, ThreadPoolExecutor$Worker (java.util.concurrent)
run:61, TaskThread$WrappingRunnable (org.apache.tomcat.util.threads)
run:834, Thread (java.lang)
总结
其实就是在DispatcherServlet类的doDispatch方法里处理了
1.执行每个拦截器的前置方法
2.执行业务类的业务方法
3.执行每个拦截器的后置方法
