Spring 源码解析之HandlerAdapter源码解析(二)
前言
看这篇之前需要有Spring 源码解析之HandlerMapping源码解析(一)
这篇的基础,这篇主要是把请求流程中的调用controller流程单独拿出来了
解决上篇文章遗留的问题
getHandler(processedRequest)
这个方法是如何查找到对应处理的HandlerExecutionChain和HandlerMapping的,比如说静态资源的处理和请求的处理肯定是不同的HandlerMappinggetHandlerAdapter(mappedHandler.getHandler());
如果取到对应的HandlerAdapter
问题一
先来看DispatcherServlet中HandlerMapping初始化,从下属代码看来,其实HandlerMapping的初始化工作并不在DispatcherServlet,而是在Spring初始化的地方,这里只不过是把所有的HandlerMapping加载到DispatcherServlet中,并且排序生成集合
private void initHandlerMappings(ApplicationContext context) { this.handlerMappings = null; if (this.detectAllHandlerMappings) { Map<String, HandlerMapping> matchingBeans = BeanFactoryUtils.beansOfTypeIncludingAncestors(context, HandlerMapping.class, true, false); if (!matchingBeans.isEmpty()) { this.handlerMappings = new ArrayList<HandlerMapping>(matchingBeans.values()); AnnotationAwareOrderComparator.sort(this.handlerMappings); } } else { try { HandlerMapping hm = context.getBean(HANDLER_MAPPING_BEAN_NAME, HandlerMapping.class); this.handlerMappings = Collections.singletonList(hm); } catch (NoSuchBeanDefinitionException ex) { } } if (this.handlerMappings == null) { this.handlerMappings = getDefaultStrategies(context, HandlerMapping.class); if (logger.isDebugEnabled()) { logger.debug("No HandlerMappings found in servlet '" + getServletName() + "': using default"); } } }
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接下来是查找适合的HandlerExecutionChain,从代码来看,上面的排序代码AnnotationAwareOrderComparator.sort(this.handlerMappings);
是有很大用处的,从这段代码逻辑来看,其实是通过for循环优先找到排在最前面并且适合的HandlerExecutionChain,从上一篇《Spring 源码解析之HandlerMapping源码解析(一)》文章可知,我这里大概初始化了十种处理请求的handlerMappings,普通的页面请求和json请求都是通过RequestMappingHandlerMapping进行处理的
protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { for (HandlerMapping hm : this.handlerMappings) { if (logger.isTraceEnabled()) { logger.trace( "Testing handler map [" + hm + "] in DispatcherServlet with name '" + getServletName() + "'"); } HandlerExecutionChain handler = hm.getHandler(request); if (handler != null) { return handler; } } return null; }@Override public final HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { Object handler = getHandlerInternal(request); if (handler == null) { handler = getDefaultHandler(); } if (handler == null) { return null; } if (handler instanceof String) { String handlerName = (String) handler; handler = getApplicationContext().getBean(handlerName); } HandlerExecutionChain executionChain = getHandlerExecutionChain(handler, request); if (CorsUtils.isCorsRequest(request)) { CorsConfiguration globalConfig = this.corsConfigSource.getCorsConfiguration(request); CorsConfiguration handlerConfig = getCorsConfiguration(handler, request); CorsConfiguration config = (globalConfig != null ? globalConfig.combine(handlerConfig) : handlerConfig); executionChain = getCorsHandlerExecutionChain(request, executionChain, config); } return executionChain; } protected HandlerMethod getHandlerInternal(HttpServletRequest request) throws Exception { String lookupPath = getUrlPathHelper().getLookupPathForRequest(request); if (logger.isDebugEnabled()) { logger.debug("Looking up handler method for path " + lookupPath); } this.mappingRegistry.acquireReadLock(); try { HandlerMethod handlerMethod = lookupHandlerMethod(lookupPath, request); if (logger.isDebugEnabled()) { if (handlerMethod != null) { logger.debug("Returning handler method [" + handlerMethod + "]"); } else { logger.debug("Did not find handler method for [" + lookupPath + "]"); } } return (handlerMethod != null ? handlerMethod.createWithResolvedBean() : null); } finally { this.mappingRegistry.releaseReadLock(); } } protected HandlerMethod lookupHandlerMethod(String lookupPath, HttpServletRequest request) throws Exception { List<Match> matches = new ArrayList<Match>(); List<T> directPathMatches = this.mappingRegistry.getMappingsByUrl(lookupPath); if (directPathMatches != null) { addMatchingMappings(directPathMatches, matches, request); } if (matches.isEmpty()) { addMatchingMappings(this.mappingRegistry.getMappings().keySet(), matches, request); } if (!matches.isEmpty()) { Comparator<Match> comparator = new MatchComparator(getMappingComparator(request)); Collections.sort(matches, comparator); if (logger.isTraceEnabled()) { logger.trace("Found " + matches.size() + " matching mapping(s) for [" + lookupPath + "] : " + matches); } Match bestMatch = matches.get(0); if (matches.size() > 1) { if (CorsUtils.isPreFlightRequest(request)) { return PREFLIGHT_AMBIGUOUS_MATCH; } Match secondBestMatch = matches.get(1); if (comparator.compare(bestMatch, secondBestMatch) == 0) { Method m1 = bestMatch.handlerMethod.getMethod(); Method m2 = secondBestMatch.handlerMethod.getMethod(); throw new IllegalStateException("Ambiguous handler methods mapped for HTTP path '" + request.getRequestURL() + "': {" + m1 + ", " + m2 + "}"); } } handleMatch(bestMatch.mapping, lookupPath, request); return bestMatch.handlerMethod; } else { return handleNoMatch(this.mappingRegistry.getMappings().keySet(), lookupPath, request); } } protected HandlerExecutionChain getHandlerExecutionChain(Object handler, HttpServletRequest request) { HandlerExecutionChain chain = (handler instanceof HandlerExecutionChain ? (HandlerExecutionChain) handler : new HandlerExecutionChain(handler)); String lookupPath = this.urlPathHelper.getLookupPathForRequest(request); for (HandlerInterceptor interceptor : this.adaptedInterceptors) { if (interceptor instanceof MappedInterceptor) { MappedInterceptor mappedInterceptor = (MappedInterceptor) interceptor; if (mappedInterceptor.matches(lookupPath, this.pathMatcher)) { chain.addInterceptor(mappedInterceptor.getInterceptor()); } } else { chain.addInterceptor(interceptor); } } return chain; }
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大致流程如上面代码,所示其实核心无非就是把url和controller里面的method关联起来,通过查找去找到合适的
问题二
如何根据合适的找到合适的HandlerAdapter
,看看下面代码
protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException { for (HandlerAdapter ha : this.handlerAdapters) { if (logger.isTraceEnabled()) { logger.trace("Testing handler adapter [" + ha + "]"); } if (ha.supports(handler)) { return ha; } } throw new ServletException("No adapter for handler [" + handler + "]: The DispatcherServlet configuration needs to include a HandlerAdapter that supports this handler"); } @Override public final boolean supports(Object handler) { return (handler instanceof HandlerMethod && supportsInternal((HandlerMethod) handler)); } @Override protected boolean supportsInternal(HandlerMethod handlerMethod) { return true; }
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从上面看来,其实想定义自己的HandlerAdapter也是可以的,只要把排序的Order设置大一些,优先找到自定义的HandlerAdapter即可
HandlerAdapter功能介绍
这里再次详细介绍一下HandlerAdapter,HandlerAdapter实现大概分为以下几种
1.RequestMappingHandlerAdapter(3.1之前是AnnotationMethodHandlerAdapter)
这里我就直接先分析RequestMappingHandlerAdapter
,大致类图如上所示,RequestMappingHandlerAdapter主要作用是调用相应的HandlerMethod,并把参数封装成具体method需要的格式,初始化的时候RequestMappingHandlerAdapter默认加载了如下的参数解析方式
private List<HandlerMethodArgumentResolver> getDefaultArgumentResolvers() { List<HandlerMethodArgumentResolver> resolvers = new ArrayList<HandlerMethodArgumentResolver>(); resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), false)); resolvers.add(new RequestParamMapMethodArgumentResolver()); resolvers.add(new PathVariableMethodArgumentResolver()); /** @RequestMapping(value = "/index/article/{id:\\d+}", produces = MediaType.APPLICATION_JSON_UTF8_VALUE) public String getArticleDetail(@PathVariable Map map) { int id=0; */ resolvers.add(new PathVariableMapMethodArgumentResolver()); resolvers.add(new MatrixVariableMethodArgumentResolver()); resolvers.add(new MatrixVariableMapMethodArgumentResolver()); resolvers.add(new ServletModelAttributeMethodProcessor(false)); resolvers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice)); resolvers.add(new RequestPartMethodArgumentResolver(getMessageConverters(), this.requestResponseBodyAdvice)); resolvers.add(new RequestHeaderMethodArgumentResolver(getBeanFactory())); resolvers.add(new RequestHeaderMapMethodArgumentResolver()); resolvers.add(new ServletCookieValueMethodArgumentResolver(getBeanFactory())); resolvers.add(new ExpressionValueMethodArgumentResolver(getBeanFactory())); /** Resolves request-related method argument values of the following types: WebRequest ServletRequest MultipartRequest HttpSession Principal Locale TimeZone (as of Spring 4.0) ZoneId (as of Spring 4.0 and Java 8) InputStream Reader HttpMethod (as of Spring 4.0) **/ resolvers.add(new ServletRequestMethodArgumentResolver()); /** * ServletResponse * OutputStream * Writer **/ resolvers.add(new ServletResponseMethodArgumentResolver()); resolvers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.requestResponseBodyAdvice)); resolvers.add(new RedirectAttributesMethodArgumentResolver()); resolvers.add(new ModelMethodProcessor()); resolvers.add(new MapMethodProcessor()); resolvers.add(new ErrorsMethodArgumentResolver()); resolvers.add(new SessionStatusMethodArgumentResolver()); resolvers.add(new UriComponentsBuilderMethodArgumentResolver()); if (getCustomArgumentResolvers() != null) { resolvers.addAll(getCustomArgumentResolvers()); } resolvers.add(new RequestParamMethodArgumentResolver(getBeanFactory(), true)); resolvers.add(new ServletModelAttributeMethodProcessor(true)); return resolvers; }
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通过上述的代码表明,RequestMappingHandlerAdapter
封装了所有的参数解析,继续看核心内容,handlerAdapter对方法的调用逻辑如下
@Override protected ModelAndView handleInternal(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ModelAndView mav = null; checkRequest(request); /** Set if controller execution should be synchronized on the session, to serialize parallel invocations from the same client. More specifically, the execution of the handleRequestInternal method will get synchronized if this flag is "true". The best available session mutex will be used for the synchronization; ideally, this will be a mutex exposed by HttpSessionMutexListener. The session mutex is guaranteed to be the same object during the entire lifetime of the session, available under the key defined by the SESSION_MUTEX_ATTRIBUTE constant. It serves as a safe reference to synchronize on for locking on the current session. In many cases, the HttpSession reference itself is a safe mutex as well, since it will always be the same object reference for the same active logical session. However, this is not guaranteed across different servlet containers; the only 100% safe way is a session mutex. */ if (this.synchronizeOnSession) { HttpSession session = request.getSession(false); if (session != null) { Object mutex = WebUtils.getSessionMutex(session); synchronized (mutex) { mav = invokeHandlerMethod(request, response, handlerMethod); } } } mav = invokeHandlerMethod(request, response, handlerMethod); if (getSessionAttributesHandler(handlerMethod).hasSessionAttributes()) { applyCacheSeconds(response, this.cacheSecondsForSessionAttributeHandlers); } else { prepareResponse(response); } return mav; }
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invokeHandlerMethod(request, response, handlerMethod)
是具体调用Controller的部分
protected ModelAndView invokeHandlerMethod(HttpServletRequest request, HttpServletResponse response, HandlerMethod handlerMethod) throws Exception { ServletWebRequest webRequest = new ServletWebRequest(request, response); WebDataBinderFactory binderFactory = getDataBinderFactory(handlerMethod); ModelFactory modelFactory = getModelFactory(handlerMethod, binderFactory); ServletInvocableHandlerMethod invocableMethod = createInvocableHandlerMethod(handlerMethod); invocableMethod.setHandlerMethodArgumentResolvers(this.argumentResolvers); 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(); if (logger.isDebugEnabled()) { logger.debug("Found concurrent result value [" + result + "]"); } invocableMethod = invocableMethod.wrapConcurrentResult(result); } invocableMethod.invokeAndHandle(webRequest, mavContainer); if (asyncManager.isConcurrentHandlingStarted()) { return null; } return getModelAndView(mavContainer, modelFactory, webRequest); }
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上面调用了invocableMethod.invokeAndHandle(webRequest, mavContainer)
,这个方法在ServletInvocableHandlerMethod中具体实现如下
public void invokeAndHandle(ServletWebRequest webRequest, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object returnValue = invokeForRequest(webRequest, mavContainer, providedArgs); setResponseStatus(webRequest); if (returnValue == null) { if (isRequestNotModified(webRequest) || hasResponseStatus() || mavContainer.isRequestHandled()) { mavContainer.setRequestHandled(true); return; } } else if (StringUtils.hasText(this.responseReason)) { mavContainer.setRequestHandled(true); return; } mavContainer.setRequestHandled(false); try { this.returnValueHandlers.handleReturnValue( returnValue, getReturnValueType(returnValue), mavContainer, webRequest); } catch (Exception ex) { if (logger.isTraceEnabled()) { logger.trace(getReturnValueHandlingErrorMessage("Error handling return value", returnValue), ex); } throw ex; } } public Object invokeForRequest(NativeWebRequest request, ModelAndViewContainer mavContainer, Object... providedArgs) throws Exception { Object[] args = getMethodArgumentValues(request, mavContainer, providedArgs); if (logger.isTraceEnabled()) { StringBuilder sb = new StringBuilder("Invoking ["); sb.append(getBeanType().getSimpleName()).append("."); sb.append(getMethod().getName()).append("] method with arguments "); sb.append(Arrays.asList(args)); logger.trace(sb.toString()); } Object returnValue = doInvoke(args); if (logger.isTraceEnabled()) { logger.trace("Method [" + getMethod().getName() + "] returned [" + returnValue + "]"); } return returnValue; } protected Object doInvoke(Object... args) throws Exception { ReflectionUtils.makeAccessible(getBridgedMethod()); try { return getBridgedMethod().invoke(getBean(), args); } catch (IllegalArgumentException ex) { assertTargetBean(getBridgedMethod(), getBean(), args); String message = (ex.getMessage() != null ? ex.getMessage() : "Illegal argument"); throw new IllegalStateException(getInvocationErrorMessage(message, args), ex); } catch (InvocationTargetException ex) { Throwable targetException = ex.getTargetException(); if (targetException instanceof RuntimeException) { throw (RuntimeException) targetException; } else if (targetException instanceof Error) { throw (Error) targetException; } else if (targetException instanceof Exception) { throw (Exception) targetException; } else { String msg = getInvocationErrorMessage("Failed to invoke controller method", args); throw new IllegalStateException(msg, targetException); } } }
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2.SimpleServletHandlerAdapter
看名字就能够大致猜到这个类的作用,SimpleServletHandlerAdapter
从翻译上来说叫做简单的Servlet处理适配器,源码如下所示,看起来确实没有几句代码,大致英文解释(Adapter to use the Servlet interface with the generic DispatcherServlet.Calls the Servlet’s {@code service} method to handle a request)。大概就是说可以用Spring去管理Servlet,这样就可以在Spring中使用Servlet,这就是说Servlet可以使用ioc和aop的一些功能了,但是感觉这样的使用场景并不多,所以也很少使用,其次还有另外一种使用Spring管理Servlet的方式,就是采用全注解配置DispatcherServlet的方式,所以感觉这个adapter没有太大用处
public class SimpleServletHandlerAdapter implements HandlerAdapter { @Override public boolean supports(Object handler) { return (handler instanceof Servlet); } @Override public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { ((Servlet) handler).service(request, response); return null; } @Override public long getLastModified(HttpServletRequest request, Object handler) { return -1; }}
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参照网上的实习代码如下所示,servlet的bean name代表了请求路径:
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" xmlns:ehcache="http://www.springmodules.org/schema/ehcache" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd http://www.springmodules.org/schema/ehcache http://www.springmodules.org/schema/cache/springmodules-ehcache.xsd" default-lazy-init="true"> <context:component-scan base-package="com.demo"> <context:include-filter type="annotation" expression="org.springframework.stereotype.Service" /> </context:component-scan> <bean id="servletHandlerAdapter" class="org.springframework.web.servlet.handler.SimpleServletHandlerAdapter"/> <bean name="/demo.do" class="com.demo.DemoServlet"/> </beans>
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3.SimpleControllerHandlerAdapter
The Controller interface is explicitly designed to operate on HttpServletRequest and HttpServletResponse objects, just like an HttpServlet. It does not aim to decouple itself from the Servlet API
上面英文大概意思就是,让Controller的用法像使用servlet一样,需要Controller实现Controller接口,实现代码如下,无非就是直接调用Controller方法
public class SimpleControllerHandlerAdapter implements HandlerAdapter { @Override public boolean supports(Object handler) { return (handler instanceof Controller); } @Override public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { return ((Controller) handler).handleRequest(request, response); } @Override public long getLastModified(HttpServletRequest request, Object handler) { if (handler instanceof LastModified) { return ((LastModified) handler).getLastModified(request); } return -1L; }}
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总结
本文在这次介绍中总共留下几个流程没有讲述,在接下来的里面会更详细的介绍
1. WebDataBinderFactory 也就是@InitBinder实现的流程?
2. WebAsyncManager 和AsyncWebRequest 这些都是异步请求的管理?
3. Spring是如何知道请求对应Controller的方法的?
4. Spring模板的渲染机制?