springmvc九大组件之HandlerAdapter详解

2023-11-18 08:46:24 作者：morris131

这篇文章主要介绍了springmvc九大组件之HandlerAdapter详解,RequestMappingHandlerAdapter支持的handler的类型是HandlerMethod,而HandlerMethod是通过解析@RequestMapping注解获得的,需要的朋友可以参考下

HandlerAdapter

HandlerAdapter处理器适配器用来执行Controller中的目标方法，由于上面有三种HandlerMapping，对应这里三种HandlerAdapter：

RequestMappingHandlerAdapter：对应RequestMappingHandlerMapping
HttpRequestHandlerAdapter：对应SimpleUrlHandlerMapping
SimpleControllerHandlerAdapter：对应BeanNameUrlHandlerMapping

当然还有SimpleServletHandlerAdapter负责处理servlet请求，默认不开启，用得少。

RequestMappingHandlerAdapter

根据handler获得HandlerAdapter

RequestMappingHandlerAdapter支持的handler的类型是HandlerMethod，而HandlerMethod是通过解析@RequestMapping注解获得的。

org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter#supports

public final boolean supports(Object handler) {
	/**
		 * supportsInternal返回true
		 * @see RequestMappingHandlerAdapter#supportsInternal(org.springframework.web.method.HandlerMethod) 
		 */
	return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler));
}

handler的执行

RequestMappingHandlerAdapter通过反射执行HandlerMethod。

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#handleInternal

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...
		// 调用handlerMethod
		mav = invokeHandlerMethod(request, response, handlerMethod);
	}

	if (!response.containsHeader(HEADER_CACHE_CONTROL)) {
		if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) {
			applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers);
		}
		else {
			prepareResponse(response);
		}
	}

	return mav;
}

将HandlerMethod封装为ServletInvocableHandlerMethod，ServletInvocableHandlerMethod负责真正的方法调用。

org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#invokeHandlerMethod

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负责真正的方法调用
		ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod);
		if (this.argumentResolvers != null) {
			invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers);
		}
		if (this.returnValueHandlers != null) {
			invocableMethod.setHandlerMethodReturnValueHandlers(this.returnValueHandlers);
		}
		invocableMethod.setDataBinderFactory(binderFactory);
		invocableMethod.setParameterNameDiscoverer(this.parameterNameDiscoverer);

		ModelAndViewContainer mavContainer = new ModelAndViewContainer();
		mavContainer.addAllAttributes(RequestContextUtils.getInputFlashMap(request));
		// 处理@ModelAttribute注解
		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);
		}

		// 反射调用controller中的方法
		invocableMethod.invokeAndHandle(webRequest, mavContainer);
		if (asyncManager.isConcurrentHandlingStarted()) {
			return null;
		}

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

requestHandled为false表示后面还需要进行视图解析，requestHandled为true表示后面不需要进行视图解析，可以直接返回响应。

org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod#invokeAndHandle

public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer,
								Object... providedArgs) throws Exception {

	// 反射调用controller中的方法
	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;
	}

	// requestHandled用来表示后面是否还需要进行视图解析
	mavContainer.setRequestHandled(false);
	Assert.state(this.returnValueHandlers != null, "No return value handlers");
	try {
		// 对返回结果进行处理
		this.returnValueHandlers.handleReturnValue(
			returnValue, getReturnValueType(returnValue), mavContainer, webRequest);
	}
	catch (Exception ex) {
		if (logger.isTraceEnabled()) {
			logger.trace(formatErrorForReturnValue(returnValue), ex);
		}
		throw ex;
	}
}

先进行参数的解析，然后反射调用controller中的方法：

org.springframework.web.method.support.InvocableHandlerMethod#invokeForRequest

	public Object invokeForRequest(NativeWebRequest request, @Nullable ModelAndViewContainer mavContainer,
			Object... providedArgs) throws Exception {

		// 方法参数解析
		Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs);
		if (logger.isTraceEnabled()) {
			logger.trace("Arguments: " + Arrays.toString(args));
		}
		// 反射调用controller中的方法
		return doInvoke(args);
	}

SimpleControllerHandlerAdapter

SimpleControllerHandlerAdapter主要负责执行类型为Controller的handler，由于handler都实现了Controller接口，只需要调用Controller接口的handleRequest()方法即可。

package org.springframework.web.servlet.mvc;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.lang.Nullable;
import org.springframework.web.servlet.HandlerAdapter;
import org.springframework.web.servlet.ModelAndView;

public class SimpleControllerHandlerAdapter implements HandlerAdapter {

	@Override
	public boolean supports(Object handler) {
		return (handler instanceof Controller);
	}

	@Override
	@Nullable
	public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		return ((Controller) handler).handleRequest(request, response);
	}
	... ...
}

HttpRequestHandlerAdapter

HttpRequestHandlerAdapter主要负责执行类型为HttpRequestHandler的handler，由于handler都实现了HttpRequestHandler接口，只需要调用Controller接口的handleRequest()方法即可。

package org.springframework.web.servlet.mvc;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.lang.Nullable;
import org.springframework.web.HttpRequestHandler;
import org.springframework.web.servlet.HandlerAdapter;
import org.springframework.web.servlet.ModelAndView;

public class HttpRequestHandlerAdapter implements HandlerAdapter {

	@Override
	public boolean supports(Object handler) {
		return (handler instanceof HttpRequestHandler);
	}

	@Override
	@Nullable
	public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception {

		((HttpRequestHandler) handler).handleRequest(request, response);
		return null;
	}
	... ...
}

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