RequestMappingHandlerAdapter支持的handler的类型是HandlerMethod，而HandlerMethod是通过解析@RequestMapping获得注释。

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)); } 

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;
	}
	... ...
}