Spring MVC请求参数的深入解析

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

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");
	}

public final boolean supports(Object handler) {
		return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
	}

// Actually invoke the handler.
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());

@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 necessary
				mav = invokeHandlerMethod(request, response, handlerMethod);
			}
		}
		else {
			// 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;
	}

mav = invokeHandlerMethod(request, response, handlerMethod);

@Nullable
	protected ModelAndView invokeHandlerMethod(HttpServletRequest request,
			HttpServletResponse response, HandlerMethod handlerMethod) throws Exception {

		ServletWebRequest webRequest = new ServletWebRequest(request, response);
		try {
            //通过处理器获得真正的执行方法及其参数列表
			ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
            //给执行方法对象添加参数解析器
			if (this.argumentResolvers != null) {
				invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
			}
            //给执行方法对象添加返回值处理器
			if (this.returnValueHandlers != null) {
				invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
			}
            //处理器对象装配完成，执行控制器方法
		invocableMethod.invokeAndHandle(webRequest, mavContainer);
		if (asyncManager.isConcurrentHandlingStarted()) {
			return null;
		}

		return getModelAndView(mavContainer, modelFactory, webRequest);
	}
	finally {
		webRequest.requestCompleted();
	}
}

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {
        //执行控制器方法
		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 {
            //处理返回值
			this.returnValueHandlers.handleReturnValue(
					returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
		}
		catch (Exception ex) {
			if (logger.isTraceEnabled()) {
				logger.trace(formatErrorForReturnValue(returnValue), ex);
			}
			throw ex;
		}
	}

public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {
    //通过参数解析器获取参数列表每一个参数的值
		Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
		if (logger.isTraceEnabled()) {
			logger.trace("Arguments: " + Arrays.toString(args));
		}
		return doInvoke(args);
	}

protected Object[] getMethodArgumentValues(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {
        //获得控制器参数列表，每一个参数包含其参数类型，参数次序、注解修饰（用于使用对应解析器）
		MethodParameter[] parameters = getMethodParameters();
		if (ObjectUtils.isEmpty(parameters)) {
			return EMPTY_ARGS;
		}

		Object[] args = new Object[parameters.length];
		for (int i = 0; i < parameters.length; i++) {
            //轮循获得参数
			MethodParameter parameter = parameters[i];
			parameter.initParameterNameDiscovery(this.parameterNameDiscoverer);
			args[i] = findProvidedArgument(parameter, providedArgs);
			if (args[i] != null) {
				continue;
			}
            //判断解析器是否支持当前参数的解析
			if (!this.resolvers.supportsParameter(parameter)) {
				throw new IllegalStateException(formatArgumentError(parameter, "No suitable resolver"));
			}
			try {
                //获得参数值的核心方法
				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;
	}

private HandlerMethodArgumentResolver getArgumentResolver(MethodParameter parameter) {
    //从缓存中获取当前参数的解析器
    HandlerMethodArgumentResolver result = this.argumentResolverCache.get(parameter);
	//缓存中不存在则将这个参数对应的解析器加到缓存中，提升后续相同请求响应速度。	
    if (result == null) {
			for (HandlerMethodArgumentResolver resolver : this.argumentResolvers) {
				if (resolver.supportsParameter(parameter)) {
					result = resolver;
					this.argumentResolverCache.put(parameter, result);
					break;
				}
			}
		}
		return result;
	}

@GetMapping(value = "/student01/{id}/car/{name}")
    public Map<String, Object> testAnnotation(@PathVariable(name = "id") String id){
        Map<String, Object> map = new HashMap<>();
        map.put("id", id);
    return map;
    }