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;
}
... ...
}
