preface
This article focuses on what the process looks like when you customize an interceptor.
The core processes
Get all interceptors first
So the project starts successfully, and then the browser requests it, and it comes up here and gets all the interceptors.
Interceptor data is stored in a collection of interceptor chain classes.
Then execute the custom interceptor
Move on to custom interceptors
In fact, every interceptor executes, that is, every interceptor in the chain of interceptors executes, and the screenshot shows the execution of a custom interceptor.
Method call stack
PreHandle: 21, LoggerInterceptor (sample.tomcat.intecepter) // Custom interceptor method applyPreHandle:136, HandlerExecutionChain (org.springframework.web.servlet) doDispatch:1033, DispatcherServlet (org. Springframework. Web. Servlet) / / MVC core method of core classes 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)Copy the codeSource code analysis
Core classes DispatcherServlet
In the doDispatch method of DispatcherServlet, the core flow is 1. Execute the pre-method of each interceptor 2. Execute the business method of the business class 3. Execute the post-method of each interceptor
/**
* 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);
}
}
}
}
Copy the codeInterceptor chain HandlerExecutionChain
Execute the preceding method
After entering the interceptor chain, the loop executes all interceptor precursors.
/** * Handler execution chain, consisting of handler object and any handler interceptors. * Returned by HandlerMapping's {@link * * @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 ++) {HandlerInterceptor interceptor = interceptors[I]; if (! Interceptor. PreHandle (request, Response, this.handler)) {// Performs the pre-interceptor method. At this point, you just execute the front method. triggerAfterCompletion(request, response, null); return false; } this.interceptorIndex = i; } } return true; }Copy the codeExecute the post-method
Executes the post-method of each interceptor
/** * Apply postHandle methods of registered interceptors. */ void applyPostHandle(HttpServletRequest request, HttpServletResponse response, 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); // Loop through the post-method for each interceptor}}}Copy the codeMethod call stack, the method call stack for the preceding method is similar.
PostHandle: 27, LoggerInterceptor (sample.tomcat.intecepter) // applyPostHandle:156, HandlerExecutionChain (org. Springframework. Web. Servlet) / / execute each interceptor method of rear doDispatch: 1045, DispatcherServlet (org. Springframework. Web. Servlet) / / core method doService core classes: 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)Copy the codeconclusion
This is done in the doDispatch method of the DispatcherServlet class
1. Execute the pre-method for each interceptor
2. Execute the business method of the business class
3. Execute the post-method for each interceptor
