目錄

一、參數注解

1.@PathVariable

2.@RequestHeader

3.@RequestParam

4.@CookieValue

5.@RequestBody

6.@RequestAttribute

7.@MatrixVariable

二、參數解析原理

1.DispatcherServlet類的doDispatch方法

2.HandlerAdapter

3.執行目標方法

4.參數解析器-HandlerMethodArgumentResolver

5.返回值處理器

三、使用Servlet API作為參數

1.使用

四、使用Servlet API作為參數原理

1.InvocableHandlerMethod的getMethodArgumentValues方法

2.HttpServletRequest作為參數的參數處理器

五、復雜參數的解析

1.使用

六、復雜參數解析原理

1.還是同樣會進入到以上的參數解析方法。

2.參數類型是Map

2.參數類型是Model

七、自定義對象參數

1.使用

八、自定義對象類型參數封裝原理

1.還是同樣會進入到以上的參數解析方法。

2.ServletModelAttributeMethodProcessor 參數處理器

3.Converters-數據類型轉換器

4.自定義Converter類型轉換器

---

一、參數注解

@PathVariable、@RequestHeader、@ModelAttribute、@RequestParam、@MatrixVariable、@CookieValue、@RequestBody、@RequestAttribute

import org.springframework.web.bind.annotation.*; import javax.servlet.http.Cookie; import java.util.HashMap; import java.util.List; import java.util.Map;@RestController public class ParameterTestController {/*** 數據綁定：頁面提交的請求數據（GET、POST）都可以和對象屬性進行綁定* @param person* @return*/@PostMapping("/saveuser")public Person saveuser(Person person){return person;}// car/2/owner/zhangsan@GetMapping("/car/{id}/owner/{username}")public Map<String,Object> getCar(@PathVariable("id") Integer id,@PathVariable("username") String name,@PathVariable Map<String,String> pv,@RequestHeader("User-Agent") String userAgent,@RequestHeader Map<String,String> header,@RequestParam("age") Integer age,@RequestParam("inters") List<String> inters,@RequestParam Map<String,String> params,@CookieValue("_ga") String _ga,@CookieValue("_ga") Cookie cookie){Map<String,Object> map = new HashMap<>();// map.put("id",id); // map.put("name",name); // map.put("pv",pv); // map.put("userAgent",userAgent); // map.put("headers",header);map.put("age",age);map.put("inters",inters);map.put("params",params);map.put("_ga",_ga);System.out.println(cookie.getName()+"===>"+cookie.getValue());return map;}@PostMapping("/save")public Map postMethod(@RequestBody String content){Map<String,Object> map = new HashMap<>();map.put("content",content);return map;}}

1.@PathVariable

（1） 獲取路徑變量的值。

@PathVariable("id") Integer id

@PathVariable("username") String name

（2）?獲取所有的路徑變量，必須使用Map<String,String>

@PathVariable Map<String,String> pv

2.@RequestHeader

（1）?獲取請求頭

@RequestHeader("User-Agent") String userAgent

（2）?獲取所有請求頭

@RequestHeader Map<String,String> header

3.@RequestParam

（1）?獲取請求參數xxxx?age=18&inters=games&inters=ball

@RequestParam("age") Integer age,

@RequestParam("inters") List<String> inters,

（2）?獲取所有請求參數

@RequestParam Map<String,String> params

4.@CookieValue

（1）?獲取某個cookie的值

@CookieValue("_ga") String _ga

（2）?獲取Cookie類型的cookie

@CookieValue("_ga") Cookie cookie

5.@RequestBody

只能用于post方式。

（1） @RequestBody String content

獲取請求體的內容

6.@RequestAttribute

獲取請求域中屬性的值。

（1）?第一種獲取轉發參數：

@RequestAttribute(value = "msg",required = false) String msg

@RequestAttribute(value = "code",required = false)Integer code

（2）?第二種獲取轉發參數

request.getAttribute("msg");

（3）?注意：

@RequestAttribute不可以用Map獲取所有的請求域的值。

Attribute更多用于設置值之后跳轉頁面，用el表達式獲取值。

@GetMapping("/goto") public String goToPage(HttpServletRequest request){request.setAttribute("msg","成功了...");request.setAttribute("code",200);return "forward:/success"; //轉發到 /success請求 }@ResponseBody @GetMapping("/success") public Map success(@RequestAttribute(value = "msg",required = false) String msg,@RequestAttribute(value = "code",required = false)Integer code,HttpServletRequest request){Object msg1 = request.getAttribute("msg");Map<String,Object> map = new HashMap<>();Object hello = request.getAttribute("hello");Object world = request.getAttribute("world");Object message = request.getAttribute("message");map.put("reqMethod_msg",msg1);map.put("annotation_msg",msg);map.put("hello",hello);map.put("world",world);map.put("message",message);return map; }

7.@MatrixVariable

矩陣變量

（1）?語法：?

請求路徑：/cars/sell;low=34;brand=byd,audi,yd

請求路徑：/cars/sell;low=34;brand=byd;brand=audi;brand=yd

請求路徑：/boss/1;age=20/2;age=10

（2）?使用

* SpringBoot默認是禁用了矩陣變量的功能

* 手動開啟：原理。對于路徑的處理。UrlPathHelper進行解析。removeSemicolonContent（移除分號內容）支持矩陣變量的。

*?矩陣變量必須有url路徑變量才能被解析。

（3）?開啟方式

①?第一種，重寫匹配規則

@Configuration(proxyBeanMethods = false) public class WebConfig implements WebMvcConfigurer {@Overridepublic void configurePathMatch(PathMatchConfigurer configurer) {UrlPathHelper urlPathHelper = new UrlPathHelper();// 設置為不移除分號“;”后面的內容。矩陣變量功能就可以生效urlPathHelper.setRemoveSemicolonContent(false);configurer.setUrlPathHelper(urlPathHelper);} }

②?第二種，直接在容器中添加組件

@Bean public WebMvcConfigurer webMvcConfigurer(){return new WebMvcConfigurer() {@Overridepublic void configurePathMatch(PathMatchConfigurer configurer) {UrlPathHelper urlPathHelper = new UrlPathHelper();// 設置為不移除分號“;”后面的內容。矩陣變量功能就可以生效urlPathHelper.setRemoveSemicolonContent(false);configurer.setUrlPathHelper(urlPathHelper);}}; }

（4）?使用代碼

// /cars/sell;low=34;brand=byd,audi,yd @GetMapping("/cars/{path}") public Map carsSell(@MatrixVariable("low") Integer low,@MatrixVariable("brand") List<String> brand,@PathVariable("path") String path){Map<String,Object> map = new HashMap<>();map.put("low",low); // 34map.put("brand",brand); // byd,audi,ydmap.put("path",path); // sellreturn map; }// /boss/1;age=20/2;age=10 @GetMapping("/boss/{bossId}/{empId}") public Map boss(@MatrixVariable(value = "age",pathVar = "bossId") Integer bossAge,@MatrixVariable(value = "age",pathVar = "empId") Integer empAge){Map<String,Object> map = new HashMap<>();map.put("bossAge",bossAge); // 20map.put("empAge",empAge); // 10return map; }

（5） 問題：做頁面開發，如果cookie被禁用了，如何獲取session？

解析：session是由每次請求攜帶的cookie中的jsessionid定位的，cookie被禁用了，就無法通過cookie查找到對應的session。

解決：使用矩陣變量，發起請求/xxx;jsessionid=xxxxx，把cookie的值使用矩陣變量的方式進行傳遞。

二、參數解析原理

springmvc處理邏輯參考博文：

springBoot-springMVC請求處理原理_A_art_xiang的博客-CSDN博客

參數解析也是從DispatcherServlet類的doDispatch方法開始研究。

1.DispatcherServlet類的doDispatch方法

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);// 找@RequestMapping注解注釋的方法，HandlerMapping中找到能處理請求的Handler（Controller.method()）// Determine handler for the current request.mappedHandler = getHandler(processedRequest);if (mappedHandler == null) {noHandlerFound(processedRequest, response);return;}// 為當前Handler 找一個適配器 HandlerAdapter； RequestMappingHandlerAdapter// 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)) {return;}// 真正的執行目標方法// Actually invoke the handler.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);}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 afterCompletionif (mappedHandler != null) {mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response);}}else {// Clean up any resources used by a multipart request.if (multipartRequestParsed) {cleanupMultipart(processedRequest);}}} }

2.HandlerAdapter

有四種處理器的適配器

?

RequestMappingHandlerAdapter支持方法上標注@RequestMapping。

HandlerFunctionAdapter支持函數式編程的。

等等 。

// org.springframework.web.servlet.DispatcherServlet#getHandlerAdapter protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException {if (this.handlerAdapters != null) {for (HandlerAdapter adapter : this.handlerAdapters) {if (adapter.supports(handler)) {return adapter;}}}throw new ServletException("No adapter for handler [" + handler +"]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler"); }

3.執行目標方法

// Actually invoke the handler. //DispatcherServlet -- doDispatch中的 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); // 以上進去之后實際是執行的RequestMappingHandlerAdapter的handleInternal方法 // RequestMappingHandlerAdapter的handleInternal方法 @Override protected ModelAndView handleInternal(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {ModelAndView mav;checkRequest(request);// Execute invokeHandlerMethod in synchronized block if required.if (this.synchronizeOnSession) {HttpSession session = request.getSession(false);if (session != null) {Object mutex = WebUtils.getSessionMutex(session);synchronized (mutex) { mav = invokeHandlerMethod(request, response, handlerMethod);}}else {// No HttpSession available -> no mutex necessarymav = invokeHandlerMethod(request, response, handlerMethod);}}else {// 真正的執行目標方法// No synchronization on session demanded at all...mav = invokeHandlerMethod(request, response, handlerMethod);}if (!response.containsHeader(HEADER_CACHE_CONTROL)) {if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);}else {prepareResponse(response);}}return mav; } // RequestMappingHandlerAdapter的invokeHandlerMethod方法 @Nullable protected ModelAndView invokeHandlerMethod(HttpServletRequest request,HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {ServletWebRequest webRequest = new ServletWebRequest(request, response);try {WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod);ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory);ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);// 注冊參數解析器-argumentResolvers，有26個。if (this.argumentResolvers != null) {invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);}// 注冊返回值處理器if (this.returnValueHandlers != null) {invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);}invocableMethod.setDataBinderFactory(binderFactory);invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);ModelAndViewContainer mavContainer = new ModelAndViewContainer();mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));modelFactory.initModel(webRequest, mavContainer, invocableMethod);mavContainer.setIgnoreDefaultModelOnRedirect(this.ignoreDefaultModelOnRedirect);AsyncWebRequest asyncWebRequest = WebAsyncUtils.createAsyncWebRequest(request, response);asyncWebRequest.setTimeout(this.asyncRequestTimeout);WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request);asyncManager.setTaskExecutor(this.taskExecutor);asyncManager.setAsyncWebRequest(asyncWebRequest);asyncManager.registerCallableInterceptors(this.callableInterceptors);asyncManager.registerDeferredResultInterceptors(this.deferredResultInterceptors);if (asyncManager.hasConcurrentResult()) {Object result = asyncManager.getConcurrentResult();mavContainer = (ModelAndViewContainer) asyncManager.getConcurrentResultContext()[0];asyncManager.clearConcurrentResult();LogFormatUtils.traceDebug(logger, traceOn -> {String formatted = LogFormatUtils.formatValue(result, !traceOn);return "Resume with async result [" + formatted + "]";});invocableMethod = invocableMethod.wrapConcurrentResult(result);}// 真正執行目標方法invocableMethod.invokeAndHandle(webRequest, mavContainer);if (asyncManager.isConcurrentHandlingStarted()) {return null;}return getModelAndView(mavContainer, modelFactory, webRequest);}finally {webRequest.requestCompleted();} } // ServletInvocableHandlerMethod的invokeAndHandle方法 public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {// 執行請求，真正的執行controller的目標方法Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs);setResponseStatus(webRequest);if (returnValue == null) {if (isRequestNotModified(webRequest) || getResponseStatus() != null || mavContainer.isRequestHandled()) {disableContentCachingIfNecessary(webRequest);mavContainer.setRequestHandled(true);return;}}else if (StringUtils.hasText(getResponseStatusReason())) {mavContainer.setRequestHandled(true);return;}mavContainer.setRequestHandled(false);Assert.state(this.returnValueHandlers != null, "No return value handlers");try {this.returnValueHandlers.handleReturnValue(returnValue, getReturnValueType(returnValue), mavContainer, webRequest);}catch (Exception ex) {if (logger.isTraceEnabled()) {logger.trace(formatErrorForReturnValue(returnValue), ex);}throw ex;} } // InvocableHandlerMethod的invokeForRequest方法 @Nullable public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {// 獲取方法所有參數的值Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);if (logger.isTraceEnabled()) {logger.trace("Arguments: " + Arrays.toString(args));}// 調用目標方法return doInvoke(args); } // InvocableHandlerMethod的getMethodArgumentValues方法，這才是如何確定目標方法每一個參數的值 protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {// 獲取所有參數MethodParameter[] parameters = getMethodParameters();if (ObjectUtils.isEmpty(parameters)) {return EMPTY_ARGS;}Object[] args = new Object[parameters.length];// 遍歷所有參數for (int i = 0; i < parameters.length; i++) {MethodParameter parameter = parameters[i];parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);args[i] = findProvidedArgument(parameter, providedArgs); // 參數名字發現器if (args[i] != null) {continue;}if (!this.resolvers.supportsParameter(parameter)) { // 判斷所有26個參數解析器是否支持該參數類型throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));}try {// args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);}catch (Exception ex) {// Leave stack trace for later, exception may actually be resolved and handled...if (logger.isDebugEnabled()) {String exMsg = ex.getMessage();if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) {logger.debug(formatArgumentError(parameter, exMsg));}}throw ex;}}return args; } // HandlerMethodArgumentResolverComposite的getArgumentResolver方法，挨個判斷所有參數解析器那個支持解析這個參數 @Nullable private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);if (result == null) {for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {if (resolver.supportsParameter(parameter)) { // 判斷是否支持解析result = resolver;this.argumentResolverCache.put(parameter, result); // 緩存，第一次執行可能會慢，以后就會很快。break;}}}return result; }

4.參數解析器-HandlerMethodArgumentResolver

確定將要執行的目標方法的每一個參數的值是什么;

SpringMVC目標方法能寫多少種參數類型。取決于參數解析器。

（1）26個參數解析器

?（2）參數解析器實際是個接口

?

*?判斷當前解析器是否支持解析這種參數

* 支持就調用 resolveArgument

最終參數解析時，調用各自 HandlerMethodArgumentResolver 的 resolveArgument 方法即可

5.返回值處理器

有以下返回值可寫：

?

三、使用Servlet API作為參數

WebRequest、ServletRequest、MultipartRequest、 HttpSession、javax.servlet.http.PushBuilder、Principal、InputStream、Reader、HttpMethod、Locale、TimeZone、ZoneId

1.使用

@GetMapping("/test") public String test(HttpServletRequest request){return "success"; }

四、使用Servlet API作為參數原理

1.InvocableHandlerMethod的getMethodArgumentValues方法

同上，也會來到InvocableHandlerMethod的getMethodArgumentValues方法，這才是如何確定目標方法每一個參數的值

// InvocableHandlerMethod的getMethodArgumentValues方法，這才是如何確定目標方法每一個參數的值 protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,Object... providedArgs) throws Exception {// 獲取所有參數MethodParameter[] parameters = getMethodParameters();if (ObjectUtils.isEmpty(parameters)) {return EMPTY_ARGS;}Object[] args = new Object[parameters.length];// 遍歷所有參數for (int i = 0; i < parameters.length; i++) {MethodParameter parameter = parameters[i];parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);args[i] = findProvidedArgument(parameter, providedArgs); // 參數名字發現器if (args[i] != null) {continue;}if (!this.resolvers.supportsParameter(parameter)) { // 判斷所有26個參數解析器是否支持該參數類型throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));}try {//args[i] = this.resolvers.resolveArgument(parameter, mavContainer, request, this.dataBinderFactory);}catch (Exception ex) {// Leave stack trace for later, exception may actually be resolved and handled...if (logger.isDebugEnabled()) {String exMsg = ex.getMessage();if (exMsg != null && !exMsg.contains(parameter.getExecutable().toGenericString())) {logger.debug(formatArgumentError(parameter, exMsg));}}throw ex;}}return args; } // HandlerMethodArgumentResolverComposite的getArgumentResolver方法，挨個判斷所有參數解析器那個支持解析這個參數 @Nullable private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);if (result == null) {for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) { // 循環判斷所有26個參數解析器是否支持該參數類型if (resolver.supportsParameter(parameter)) { // 判斷是否支持解析result = resolver;this.argumentResolverCache.put(parameter, result); // 緩存，第一次執行可能會慢，以后就會很快。break;}}}return result; }

2.HttpServletRequest作為參數的參數處理器

ServletRequestMethodArgumentResolver?解析以上的部分參數（WebRequest、ServletRequest、MultipartRequest、 HttpSession、javax.servlet.http.PushBuilder、Principal、InputStream、Reader、HttpMethod、Locale、TimeZone、ZoneId）

@Override public boolean supportsParameter(MethodParameter parameter) {Class<?> paramType = parameter.getParameterType();return (WebRequest.class.isAssignableFrom(paramType) ||ServletRequest.class.isAssignableFrom(paramType) ||MultipartRequest.class.isAssignableFrom(paramType) ||HttpSession.class.isAssignableFrom(paramType) ||(pushBuilder != null && pushBuilder.isAssignableFrom(paramType)) ||Principal.class.isAssignableFrom(paramType) ||InputStream.class.isAssignableFrom(paramType) ||Reader.class.isAssignableFrom(paramType) ||HttpMethod.class == paramType ||Locale.class == paramType ||TimeZone.class == paramType ||ZoneId.class == paramType); }@Override public Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {Class<?> paramType = parameter.getParameterType();// WebRequest / NativeWebRequest / ServletWebRequestif (WebRequest.class.isAssignableFrom(paramType)) {if (!paramType.isInstance(webRequest)) {throw new IllegalStateException("Current request is not of type [" + paramType.getName() + "]: " + webRequest);}return webRequest;}// ServletRequest / HttpServletRequest / MultipartRequest / MultipartHttpServletRequestif (ServletRequest.class.isAssignableFrom(paramType) || MultipartRequest.class.isAssignableFrom(paramType)) {return resolveNativeRequest(webRequest, paramType);}// HttpServletRequest required for all further argument typesreturn resolveArgument(paramType, resolveNativeRequest(webRequest, HttpServletRequest.class)); }

五、復雜參數的解析

Map、Model（map、model里面的數據會被放在request的請求域 request.setAttribute）、Errors/BindingResult、RedirectAttributes（ 重定向攜帶數據）、ServletResponse（response）、SessionStatus、UriComponentsBuilder、ServletUriComponentsBuilder

1.使用

@GetMapping("/params") public String testParam(Map<String,Object> map,Model model,HttpServletRequest request,HttpServletResponse response){map.put("hello","world666");model.addAttribute("world","hello666");request.setAttribute("message","HelloWorld");Cookie cookie = new Cookie("c1","v1");response.addCookie(cookie);return "forward:/success"; }@ResponseBody @GetMapping("/success") public Map success(HttpServletRequest request){Map<String,Object> map = new HashMap<>();Object hello = request.getAttribute("hello");Object world = request.getAttribute("world");Object message = request.getAttribute("message");map.put("hello",hello);map.put("world",world);map.put("message",message);return map; }

Map<String,Object> map,??Model model, HttpServletRequest request 都是可以給request域中放數據，可以使用request.getAttribute();獲取數據，也可以在頁面使用el表達式獲取。

六、復雜參數解析原理

1.還是同樣會進入到以上的參數解析方法。

2.參數類型是Map

會使用MapMethodProcessor參數解析器。

public class MapMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {// 判斷是否用該參數解析器解析@Overridepublic boolean supportsParameter(MethodParameter parameter) {return Map.class.isAssignableFrom(parameter.getParameterType()) &&parameter.getParameterAnnotations().length == 0;}// 解析@Override@Nullablepublic Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");return mavContainer.getModel(); // 返回一個BindingAwareModelMap，既是Model 也是Map。} } // ModelAndViewContainer的getModel方法 public ModelMap getModel() {if (useDefaultModel()) {return this.defaultModel;}else {if (this.redirectModel == null) {this.redirectModel = new ModelMap();}return this.redirectModel;} }

?目標方法執行完成，將所有的數據都放在 ModelAndViewContainer；包含要去的頁面地址View。還包含Model數據。

@Nullable private ModelAndView getModelAndView(ModelAndViewContainer mavContainer,ModelFactory modelFactory, NativeWebRequest webRequest) throws Exception {modelFactory.updateModel(webRequest, mavContainer);if (mavContainer.isRequestHandled()) {return null;}ModelMap model = mavContainer.getModel();ModelAndView mav = new ModelAndView(mavContainer.getViewName(), model, mavContainer.getStatus());if (!mavContainer.isViewReference()) {mav.setView((View) mavContainer.getView());}if (model instanceof RedirectAttributes) {Map<String, ?> flashAttributes = ((RedirectAttributes) model).getFlashAttributes();HttpServletRequest request = webRequest.getNativeRequest(HttpServletRequest.class);if (request != null) {RequestContextUtils.getOutputFlashMap(request).putAll(flashAttributes);}}return mav; }

處理派發結果：

processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); -> renderMergedOutputModel(mergedModel, getRequestToExpose(request), response);InternalResourceView：視圖解析流程 @Override protected void renderMergedOutputModel(Map<String, Object> model, HttpServletRequest request, HttpServletResponse response) throws Exception {// 暴露模型作為請求域屬性// Expose the model object as request attributes.exposeModelAsRequestAttributes(model, request);// Expose helpers as request attributes, if any.exposeHelpers(request);// Determine the path for the request dispatcher.String dispatcherPath = prepareForRendering(request, response);// Obtain a RequestDispatcher for the target resource (typically a JSP).RequestDispatcher rd = getRequestDispatcher(request, dispatcherPath);if (rd == null) {throw new ServletException("Could not get RequestDispatcher for [" + getUrl() +"]: Check that the corresponding file exists within your web application archive!");}// If already included or response already committed, perform include, else forward.if (useInclude(request, response)) {response.setContentType(getContentType());if (logger.isDebugEnabled()) {logger.debug("Including [" + getUrl() + "]");}rd.include(request, response);}else {// Note: The forwarded resource is supposed to determine the content type itself.if (logger.isDebugEnabled()) {logger.debug("Forwarding to [" + getUrl() + "]");}rd.forward(request, response);} } protected void exposeModelAsRequestAttributes(Map<String, Object> model,HttpServletRequest request) throws Exception {//model中的所有數據遍歷挨個放在請求域中（在頁面跳轉之前）model.forEach((name, value) -> {if (value != null) {request.setAttribute(name, value);}else {request.removeAttribute(name);}}); }

2.參數類型是Model

會使用ModelMethodProcessor參數解析器。

public class ModelMethodProcessor implements HandlerMethodArgumentResolver, HandlerMethodReturnValueHandler {@Overridepublic boolean supportsParameter(MethodParameter parameter) {return Model.class.isAssignableFrom(parameter.getParameterType());}@Override@Nullablepublic Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {Assert.state(mavContainer != null, "ModelAndViewContainer is required for model exposure");return mavContainer.getModel(); // 跟Map參數一樣，也返回一個BindingAwareModelMap，既是Model 也是Map。} }

七、自定義對象參數

可以自動類型轉換與格式化，可以級聯封裝

1.使用

/** * 姓名： <input name="userName"/> <br/> * 年齡： <input name="age"/> <br/> * 生日： <input name="birth"/> <br/> * 寵物姓名：<input name="pet.name"/><br/> * 寵物年齡：<input name="pet.age"/> */ @Data public class Person {private String userName;private Integer age;private Date birth;private Pet pet; }@Data public class Pet {private String name;private String age; } /** * 數據綁定：頁面提交的請求數據（GET、POST）都可以和對象屬性進行綁定 */ @PostMapping("/saveuser") public Person saveuser(Person person){return person; }

八、自定義對象類型參數封裝原理

1.還是同樣會進入到以上的參數解析方法。

2.ServletModelAttributeMethodProcessor 參數處理器

自定義類型的參數，是用ServletModelAttributeMethodProcessor 參數處理器解析的。

// ModelAttributeMethodProcessor的supportsParameter方法（ServletModelAttributeMethodProcessor繼承ModelAttributeMethodProcessor） @Override public boolean supportsParameter(MethodParameter parameter) {return (parameter.hasParameterAnnotation(ModelAttribute.class) ||(this.annotationNotRequired && !BeanUtils.isSimpleProperty(parameter.getParameterType())));// 參數是不是簡單類型，自定義對象不是簡單類型 }// org.springframework.beans.BeanUtils#isSimpleProperty public static boolean isSimpleProperty(Class<?> type) {Assert.notNull(type, "'type' must not be null");return isSimpleValueType(type) || (type.isArray() && isSimpleValueType(type.getComponentType())); } public static boolean isSimpleValueType(Class<?> type) {return (Void.class != type && void.class != type &&(ClassUtils.isPrimitiveOrWrapper(type) ||Enum.class.isAssignableFrom(type) ||CharSequence.class.isAssignableFrom(type) ||Number.class.isAssignableFrom(type) ||Date.class.isAssignableFrom(type) ||Temporal.class.isAssignableFrom(type) ||URI.class == type ||URL.class == type ||Locale.class == type ||Class.class == type)); } // org.springframework.web.method.annotation.ModelAttributeMethodProcessor#resolveArgument @Override @Nullable public final Object resolveArgument(MethodParameter parameter, @Nullable ModelAndViewContainer mavContainer,NativeWebRequest webRequest, @Nullable WebDataBinderFactory binderFactory) throws Exception {Assert.state(mavContainer != null, "ModelAttributeMethodProcessor requires ModelAndViewContainer");Assert.state(binderFactory != null, "ModelAttributeMethodProcessor requires WebDataBinderFactory");String name = ModelFactory.getNameForParameter(parameter);ModelAttribute ann = parameter.getParameterAnnotation(ModelAttribute.class);if (ann != null) {mavContainer.setBinding(name, ann.binding());}Object attribute = null;BindingResult bindingResult = null;if (mavContainer.containsAttribute(name)) {attribute = mavContainer.getModel().get(name);}else {// Create attribute instancetry {attribute = createAttribute(name, parameter, binderFactory, webRequest);}catch (BindException ex) {if (isBindExceptionRequired(parameter)) {// No BindingResult parameter -> fail with BindExceptionthrow ex;}// Otherwise, expose null/empty value and associated BindingResultif (parameter.getParameterType() == Optional.class) {attribute = Optional.empty();}bindingResult = ex.getBindingResult();}}if (bindingResult == null) {// Bean property binding and validation;// skipped in case of binding failure on construction.// attribute就是創建的空實體類對象（Person），webRequest就是原生的request請求。// WebDataBinder :web數據綁定器，將請求參數的值綁定到指定的JavaBean里面// WebDataBinder 利用它里面的 Converters 將請求數據轉成指定的數據類型。再次封裝到JavaBean中WebDataBinder binder = binderFactory.createBinder(webRequest, attribute, name);if (binder.getTarget() != null) {if (!mavContainer.isBindingDisabled(name)) {// 關鍵一步，幫我們把請求里的數據綁定到Person對象，執行的是ServletModelAttributeMethodProcessor類的方法。// 綁定過程中，有使用到Converter類型轉換器，因為http都是string，如果對象有Integer等類型需要進行轉換。bindRequestParameters(binder, webRequest);}validateIfApplicable(binder, parameter);if (binder.getBindingResult().hasErrors() && isBindExceptionRequired(binder, parameter)) {throw new BindException(binder.getBindingResult());}}// Value type adaptation, also covering java.util.Optionalif (!parameter.getParameterType().isInstance(attribute)) {attribute = binder.convertIfNecessary(binder.getTarget(), parameter.getParameterType(), parameter);}bindingResult = binder.getBindingResult();}// Add resolved attribute and BindingResult at the end of the modelMap<String, Object> bindingResultModel = bindingResult.getModel();mavContainer.removeAttributes(bindingResultModel);mavContainer.addAllAttributes(bindingResultModel);return attribute; }

GenericConversionService類：在設置每一個值的時候，找它里面的所有converter那個可以將這個數據類型（request帶來參數的字符串）轉換到指定的類型（JavaBean -- Integer）（文件上傳：byte -- > file）

3.Converters-數據類型轉換器

WebDataBinder 利用它里面的 Converters 將請求數據轉成指定的數據類型。再次通過反射封裝到JavaBean中。

?

?

4.自定義Converter類型轉換器

未來我們可以給WebDataBinder里面放自己的Converter（T就是要轉換的類型）；

private static final class StringToNumber<T extends Number> implements Converter<String, T>

（1）新需求：假設寵物輸入“貓,3”，就以“,”分割，前后參數分別綁定到Pet的name和age。

/** * 姓名： <input name="userName"/> <br/> * 年齡： <input name="age"/> <br/> * 生日： <input name="birth"/> <br/> * 寵物：<input name="pet"/> */ @Data public class Person {private String userName;private Integer age;private Date birth;private Pet pet; }@Data public class Pet {private String name;private String age; }

（2）定義config類

import com.cxf.model.Pet; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.core.convert.converter.Converter; import org.springframework.format.FormatterRegistry; import org.springframework.util.StringUtils; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;@Configuration(proxyBeanMethods = false) public class WebConfig{//WebMvcConfigurer定制化SpringMVC的功能@Beanpublic WebMvcConfigurer webMvcConfigurer(){return new WebMvcConfigurer() {@Overridepublic void addFormatters(FormatterRegistry registry) {// 添加一個String->Pet的類型轉換器registry.addConverter(new Converter<String, Pet>() {@Overridepublic Pet convert(String source) {// 貓,3if(!StringUtils.isEmpty(source)){Pet pet = new Pet();String[] split = source.split(",");pet.setName(split[0]);pet.setAge(Integer.parseInt(split[1]));return pet;}return null;}});}};} }

（3）測試一下

http://localhost:8080/person?userName=zhangsan&age=18&birth=1992/12/12&pet=mao,3

{"userName":"zhangsan","age":18,"birth":"1992-12-11T16:00:00.000+00:00","pet":{"name":"mao","age":3}}

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