SSM-SpringMVC-04：SpringMVC深入淺出理解HandleMapping（源碼刨析）

標籤：hex   ace   處理   gpo   很多   lin   mapped   集合   tps   

 

------------吾亦無他,唯手熟爾，謙卑若愚，好學若饑-------------

 

 

先從概念理解，從中央調度器，攜帶參數request，調度到HandleMapping處理器映射器，處理器映射器返回處理器執行鏈給中央調度器

 

我從底層走一遍，印證這個概念：

　　1.都說是中央調度器的，所以先找到中央調度器DispatcherServlet

　　2.從他裡面找到一個方法   ctrl+f 找（doDistch）

 

    protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {        HttpServletRequest processedRequest = request;        HandlerExecutionChain mappedHandler = null;        boolean multipartRequestParsed = false;        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);        try {            try {                ModelAndView err = null;                Exception dispatchException = null;                try {                    processedRequest = this.checkMultipart(request);                    multipartRequestParsed = processedRequest != request;                    mappedHandler = this.getHandler(processedRequest);                    if(mappedHandler == null || mappedHandler.getHandler() == null) {                        this.noHandlerFound(processedRequest, response);                        return;                    }                    HandlerAdapter ex = this.getHandlerAdapter(mappedHandler.getHandler());                    String method = request.getMethod();                    boolean isGet = "GET".equals(method);                    if(isGet || "HEAD".equals(method)) {                        long lastModified = ex.getLastModified(request, mappedHandler.getHandler());                        if(this.logger.isDebugEnabled()) {                            this.logger.debug("Last-Modified value for [" + getRequestUri(request) + "] is: " + lastModified);                        }                        if((new ServletWebRequest(request, response)).checkNotModified(lastModified) && isGet) {                            return;                        }                    }                    if(!mappedHandler.applyPreHandle(processedRequest, response)) {                        return;                    }                    err = ex.handle(processedRequest, response, mappedHandler.getHandler());                    if(asyncManager.isConcurrentHandlingStarted()) {                        return;                    }                    this.applyDefaultViewName(processedRequest, err);                    mappedHandler.applyPostHandle(processedRequest, response, err);                } catch (Exception var19) {                    dispatchException = var19;                }                this.processDispatchResult(processedRequest, response, mappedHandler, err, dispatchException);            } catch (Exception var20) {                this.triggerAfterCompletion(processedRequest, response, mappedHandler, var20);            } catch (Error var21) {                this.triggerAfterCompletionWithError(processedRequest, response, mappedHandler, var21);            }        } finally {            if(asyncManager.isConcurrentHandlingStarted()) {                if(mappedHandler != null) {                    mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);                }            } else if(multipartRequestParsed) {                this.cleanupMultipart(processedRequest);            }        }    }

 

　　　　這個方法裡面很多內容不需要關注，需要關注的的我講講

        HttpServletRequest processedRequest = request;        //接收請求        HandlerExecutionChain mappedHandler = null;        //處理器執行鏈        boolean multipartRequestParsed = false;        //多部分請求，檔案上傳        WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);        //異部請求        try {            try {                               ModelAndView err = null;                 //視圖解析                try {                                        processedRequest = this.checkMultipart(request);                    //檢查是否是多部分請求                    multipartRequestParsed = processedRequest != request;                                        mappedHandler = this.getHandler(processedRequest);                        //這就返回處理器執行鏈

　　3.到這兒，點擊getHandler（processedRequest）查看

    protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {        Iterator var2 = this.handlerMappings.iterator();        HandlerExecutionChain handler;        do {            if(!var2.hasNext()) {                return null;            }            HandlerMapping hm = (HandlerMapping)var2.next();            if(this.logger.isTraceEnabled()) {                this.logger.trace("Testing handler map [" + hm + "] in DispatcherServlet with name \‘" + this.getServletName() + "\‘");            }            handler = hm.getHandler(request);        } while(handler == null);        return handler;    }

　　　　我把關鍵代碼提煉出來解釋一波

        //迭代器，沒做泛型，handlerMapping是list集合        Iterator var2 = this.handlerMappings.iterator();        //處理器執行鏈        HandlerExecutionChain handler;        do {            if(!var2.hasNext()) {                return null;            }            //處理器映射器            HandlerMapping hm = (HandlerMapping)var2.next();                       //繼續追蹤            handler = hm.getHandler(request);        } while(handler == null);        return handler;    

　　4.追蹤hm.getHandler(request)方法，發現他是HandlerMapping介面的，（Ctrl+H）找它的實作類別AbstractHandlerMapping,ctrl+F找getHandler

    public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception {        Object handler = this.getHandlerInternal(request);        if(handler == null) {            handler = this.getDefaultHandler();        }        if(handler == null) {            return null;        } else {            if(handler instanceof String) {                String executionChain = (String)handler;                handler = this.getApplicationContext().getBean(executionChain);            }            HandlerExecutionChain executionChain1 = this.getHandlerExecutionChain(handler, request);            if(CorsUtils.isCorsRequest(request)) {                CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request);                CorsConfiguration handlerConfig = this.getCorsConfiguration(handler, request);                CorsConfiguration config = globalConfig != null?globalConfig.combine(handlerConfig):handlerConfig;                executionChain1 = this.getCorsHandlerExecutionChain(request, executionChain1, config);            }            return executionChain1;        }    }

　　　　同樣，我把關鍵代碼提出來解釋一波

　　　　//擷取處理器        Object handler = this.getHandlerInternal(request);        //處理器為空白就用預設的        if(handler == null) {            handler = this.getDefaultHandler();        }        //預設的也是空就返回null        if(handler == null) {            return null;        } else {            //判斷是否是String類型            if(handler instanceof String) {                //這兒就是我們一般用的處理器的從設定檔bean的id                String handlerName = (String)handler;  //  /hello                //這就是Spring啊                handler = this.getApplicationContext().getBean(handlerName);            }
　　　　　　　　//擷取處理常式執行鏈

　　　　　　　　HandlerExecutionChain executionChain1 = this.getHandlerExecutionChain(handler, request);

　　　　//返回的時候變成攜帶處理器的了 
　　
　　　　return this.getHandlerExecutionChain(handler, request); }

　　5.追蹤擷取程式執行鏈,this.getHandlerExecutionChain(handler,request)

    protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) {        //三元運算式，是處理器執行鏈就強轉，不是就擷取根據處理器產生一個        HandlerExecutionChain chain = handler instanceof HandlerExecutionChain?(HandlerExecutionChain)handler:new HandlerExecutionChain(handler);        String lookupPath = this.urlPathHelper.getLookupPathForRequest(request);        Iterator var5 = this.adaptedInterceptors.iterator();        while(var5.hasNext()) {            //只需要知道這兒添加攔截器即可            HandlerInterceptor interceptor = (HandlerInterceptor)var5.next();            if(interceptor instanceof MappedInterceptor) {                MappedInterceptor mappedInterceptor = (MappedInterceptor)interceptor;                if(mappedInterceptor.matches(lookupPath, this.pathMatcher)) {                    chain.addInterceptor(mappedInterceptor.getInterceptor());                }            } else {                chain.addInterceptor(interceptor);            }        }        return chain;    }

 

SSM-SpringMVC-04：SpringMVC深入淺出理解HandleMapping（源碼刨析）