SpringMVC源碼解析 一

　　當服務器接收到從瀏覽器發送的一個請求后, 首先進入HttpServlet#service()方法中

　　HttpServlet#service()方法實現:

　　@Override

　　public void service(ServletRequest req, ServletResponse res)

　　throws ServletException, IOException {

　　HttpServletRequest request;

　　HttpServletResponse response;

　　try {

　　request = (HttpServletRequest) req;

　　response = (HttpServletResponse) res;

　　} catch (ClassCastException e) {

　　throw new ServletException(lStrings.getString("http.non_http"));

　　}

　　service(request, response);

　　}

　　protected void service(HttpServletRequest req, HttpServletResponse resp)

　　throws ServletException, IOException {

　　String method = req.getMethod();

　　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 {

　　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);

　　}

　　}

　　在HttpServlet#service(request, response)中調用根據請求類型調用不同的實現方法, doGet, doPost等; 這里發送的是get請求, 因此看doGet()的實現;

　　FrameworkServlet#doGet()方法的實現:

　　@Override

　　protected final void doGet(HttpServletRequest request, HttpServletResponse response)

　　throws ServletException, IOException {

　　proce***equest(request, response);

　　}

　　FrameworkServlet#proce***equest()方法實現:

　　protected final void proce***equest(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 {

　　/**

　　* 請求邏輯處理

　　* {@link DispatcherServlet#doService(HttpServletRequest,HttpServletResponse)}

　　*/

　　doService(request, response);

　　}

　　. . . . . .

　　}

　　DispatcherServlet#doService()方法實現

　　@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) + "]");

　　}

　　// 設置快照

　　Map 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));

　　}

　　}

　　}

　　// 使框架對象可用于處理程序并查看對象

　　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 {

　　/**

　　* 核心邏輯處理

　　*/

　　doDispatch(request, response);

　　}

　　finally {

　　if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) {

　　//使用快照恢復Request屬性

　　if (attributesSnapshot != null) {

　　restoreAttributesAfterInclude(request, attributesSnapshot);

　　}

　　}

　　}

　　}

　　DispatcherServlet#doDispatch()方法實現

　　protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception {

　　HttpServletRequest processedRequest = request;

　　HandlerExecutionChain mappedHandler = null;

　　boolean multipartRequestParsed = false;

　　WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);

　　try {鄭州人流醫院 http://www.zykdfk.com/

　　ModelAndView mv = null; //封裝view和數據信息

　　Exception dispatchException = null; //封裝異常信息

　　try {

　　processedRequest = checkMultipart(request);

　　multipartRequestParsed = (processedRequest != request);

　　/**

　　* 1. 獲取處理器

　　* mappedHandler: HandlerExecutionChain

　　*/

　　mappedHandler = getHandler(processedRequest);

　　if (mappedHandler == null) {

　　noHandlerFound(processedRequest, response);

　　return;

　　}

　　/**

　　* 2. 獲取適配器

　　*/

　　HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());

　　// 如果處理程序支持，則處理最后修改的標頭

　　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;

　　}

　　}

　　/**

　　* 執行HandlerExecutionChain中的攔截器

　　*/

　　if (!mappedHandler.applyPreHandle(processedRequest, response)) {

　　return;

　　}

　　/**

　　* 3. 通過適配器執行處理器, 也就是我們編寫的Controller類; 注意: 這里調用的是適配器的handle()方法

　　* {@link AbstractHandlerMethodAdapter#handle(HttpServletRequest, HttpServletResponse, Object)}

　　*

　　* mv: ModelAndView實例{@link AbstractHandlerMethodAdapter#handle(HttpServletRequest,HttpServletResponse, Object)}

　　*/

　　mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

　　if (asyncManager.isConcurrentHandlingStarted()) {

　　return;

　　}

　　applyDefaultViewName(processedRequest, mv);

　　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);

　　}

　　/**

　　* 4. 視圖解析

　　*/

　　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);

　　}

　　}

　　}

　　}

　　分析(注: 以下模塊解析比較復雜, 拆分為不同播客分析):

　　根據請求信息獲取對應處理器

　　根據映射處理器獲取對應的適配器

　　通過適配器執行處理器, 也就是編寫的Controller類中的相應方法

　　視圖解析

　　請求解析過程圖