SpringMVC流程及源码分析
前言
学了一遍SpringMVC以后,想着做一个总结,复习一下。复习写下面的总结的时候才发现,其实自己学的并不彻底、牢固、也没有学全,视频跟书本是要结合起来一起,每一位老师的视频可能提到的东西都不一致,也导致也不是很全面,书本上会讲的笔记系统、全面。同时我自己也是一个初学者,下面总结的可能并不完善、正确,希望看到的大神给我指出,在此非常感谢。
目录
- SpringMVC流程及源码分析
- 一 、Spring核心模块
- 二、SpringMVC流程及原理
- 1、执行流程
- 1.1、执行流程
- 1.2、执行流程说明:
- 1.2.1、第02、03说明
- 1.2.2、第04说明
- 1.2.2、SpringMVC组件说明
- 1.2.3、SpringMVC详细流程图
- 二、源码分析
- 1、初始化
- 2、前端控制器(中央处理器)DistepcherServlet
- 2.1、查找处理器映射器HandlerMapping
- 2.2、根据处理器映射器HandlerMapping返回结果调用处理器适配器HandlerAdapter
- 2.3、检查拦截器Interceptor
- 2.3、处理器适配器HandlerAdapter执行Handler(Controller)返回ModelAndView
- 2.4、视图解析器ViewResolver
- 2.5、视图View
- 2.5.1、视图对象的作用
- 2.5.2、View接口图
- 2.5.3、View的实现类图
- 2.5.4、View的UML图
- 2.5.5、常用的View视图类
- 2.6、其他重要的点
- 2.6.1、DispatcherServlet.properties
- 三、引用参考资料
一 、Spring核心模块
1、核心模块
Spring Web MVC (下文简称为 SpringMVC )是 Spring 提供 Web 应用的框架设计,属于表现层的框架。SpringMVC是Spring框架的一部分。
Spring框架包括大致六大模块,核心容器(Core Container)、AOP和设备支持、数据访问及集成、Web、报文发送、Test
图片来源于Spring官网5.0.0.M5:
https://docs.spring.io/spring-framework/docs/5.0.0.M5/spring-framework-reference/html/overview.html#overview-modules
对于Spring5模块图,有2点疑问:
1、不清楚为什么在Spring官网上5.0版本以后,Release版(稳定版)的都未找到模块图,但是在M(里程碑版)版找到 了,如果有人在5.0以后的Release版(稳定版)找到,麻烦给我留个言,谢谢。
2、在其他博文中看到Spring5模块结构图是这样的:
挺奇怪这个图是哪里来的?(路过的大神请指点)
对于问题2,我在Spring5.2.13.RELEASE GA中,找到了如下所示信息:
拷贝以上信息:
Spring Framework Documentation
Version 5.2.13.RELEASE
What's New, Upgrade Notes, Supported Versions, and other topics, independent of release cadence, are maintained externally on the project's Github Wiki.
Overview | history, design philosophy, feedback, getting started. |
---|
Core | IoC Container, Events, Resources, i18n, Validation, Data Binding, Type Conversion, SpEL, AOP. |
Testing | Mock Objects, TestContext Framework, Spring MVC Test, WebTestClient. |
Data Access | Transactions, DAO Support, JDBC, O/R Mapping, |
Web Servlet | Spring MVC, WebSocket, SockJS, STOMP Messaging. |
Web Reactive | Spring WebFlux, WebClient, WebSocket. |
Integration | Remoting, JMS, JCA, JMX, Email, Tasks, Scheduling, Caching. |
Languages | Kotlin, Groovy, Dynamic Languages. |
按照以上信息的Web Servlet、Web Reactive已经是分属于不同的模块了。
- Web Servlet:Spring MVC, WebSocket, SockJS, STOMP Messaging.
- Web Reactive:Spring WebFlux, WebClient, WebSocket.
Spring官方文档:https://spring.io/projects/spring-framework#learn/
2、Spring版本命名规则(补充)
上面提到了Spring又不同的版本,在此记录一下各个版本的意义。
描述方式 | 说明 | 含义 |
---|
Snapshot | 快照版 | 尚不稳定,仍处于开发中的版本 |
Release | 稳定版 | 功能相对稳定,可以对外发行,但有时间限制 |
GA | 正式版 | 代表广泛可用的稳定版(General Availability) |
M | 里程碑版 | (M是Milestone的意思)具有一些全新的功能或是有意义的版本 |
RC | 终测版 | Release Candidate(最终测试),即将作为正式版发布 |
二、SpringMVC流程及原理
1、执行流程
SpringMVC执行流程图
图片来源:三、引用参考资料
1.1、执行流程
01、用户发送出请求到前端控制器(中央处理器)DispatcherServlet进行处理。
02、前端控制器DispatcherServlet收到请求后,调用处理器映射器HandlerMapping。
03、处理器映射器HandlerMapping(处理器映射器)根据request请求的URL等信息查找能够进行处理的Handler,以及相关拦截器interceptor,并构造HandlerExecutionChain执行链,然后将构造好的HandlerExecutionChain执行链对象返回给前端控制器DispatcherServlet。
04、前端控制器DispatcherServlet根据处理器映射器HandlerMapping的
05、处理器适配器HandlerAdapter经过适配调用具体的处理器(Handler/Controller),即业务中自己写的Controller。
06、Controller处理完后返回ModelAndView(springmvc的封装对象,将model和view封装在一起)给处理器适配器HandlerAdapter;
07、处理器适配器HandlerAdapter将Controller执行结果ModelAndView返回给前端控制器DispatcherServlet。
08、前端控制器DispatcherServlet调用视图解析器ViewReslover处理ModelAndView。
09、视图解析器ViewReslover解析后根据逻辑视图名解析成物理视图名即具体的页面地址,生成并返回具体对象View(springmvc封装对象,是一个接口)。
10、前端控制器DispatcherServlet根据对象View进行视图渲染,填充Model。
11、前端控制器DispatcherServlet向用户返回响应
1.2、执行流程说明:
1.2.1、第02、03说明
(1) 处理器映射器:springmvc框架中的一种对象,框架把实现了HandlerMapping接口的类都叫做映射器(多个);
(2) 处理器映射器作用:根据请求,从springmvc容器对象中获取处理器对象(MyController controller = ctx.getBean("some")
(3) 框架把找到的处理器对象放到一个叫做处理器执行链(HandlerExecutionChain)的类保存
(4) HandlerExecutionchain:类中保存着
a:处理器对象(MyController);
b:项目中的所有的拦截器List
(5) 方法调用:HandlerExecutionChain mappedHandler - getHandler (processedRequest);
1.2.2、第04说明
(1) HandlerExecutionChain执行链找到对应的处理器映射器HandlerAdapter。
(2) 处理器适配器:springmvc框架中的对象,需要实现HandlerAdapter接口,
(3) 处理器适配器作用:执行处理器方法(调用MyController.doSome()得到返回值ModelAndView )
(4) 前端控制器中调用适配器:HandlerAdapter ha =getHandlerAdapter (mappedHandler.getHandler());
(5) 执行处理器方法:mv= ha.handle (processedRequest, response, mappedHandler.getHandler());
第08说明:
(1) 视图解析器:springmvc中的对象,需要实现ViewResoler接口(可以有多个)
(2) 视图解析器作用:组成视图完整路径,使用前缀,后缀。并创建View对象。
(3) view是一个接口,表示视图的,在框架中jsp,htm1不是string表示,而是使用view和他的实现类表示视图。
InternalResourceview:视图类,表示jsp文件,视图解析器会创建InternalResourceView类对象。 这个对象的里面,有一个属性url-/WEB-INF/view/show.jsp
1.2.2、SpringMVC组件说明
- (1). 前端控制器(DispatcherServlet):接收请求,响应结果,相当于电脑的CPU。
- (2). 处理器映射器(HandlerMapping):根据URL去查找处理器.
- (3). 处理器(Handler):(需要程序员去写代码处理逻辑的).
- (4). 处理器适配器(HandlerAdapter):会把处理器包装成适配器,这样就可以支持多种类型的处理器,类比笔记本的适配器(适配器模式的应用).
- (5). 视图解析器(ViewResovler):进行视图解析,多返回的字符串,进行处理,可以解析成对应的页面.
1.2.3、SpringMVC详细流程图
综上所述,总结下SpringMVC的详细流程图:
图片来源:三、引用参考资料
二、源码分析
以下源码来源jar包:spring-webmvc-5.25.RELEASE.jar
1、初始化
1.1、ApplicationContext
ApplicationContext初始化入口类:ApplicationObjectSupport的setApplicationContext方法,setApplicationContext方法中核心部分就是初始化容器initApplicationContext(context),子类AbstractDetectingUrlHandlerMapping实现了该方法。
类图:
UML图:
RequestMappingHandlerMapping ,用于注解@Controller,@RequestMapping来定义controller.
初始化时,3个类的大致分工如下:
- AbstractHandlerMethodMapping定义整个算法流程;
- RequestMappingInfoHandlerMapping提供匹配条件RequestMappingInfo的解析处理;
- RequestMappingHandlerMapping根据@RequestMapping注解生成 RequestMappingInfo,同时提供isHandler实现
2、前端控制器(中央处理器)DistepcherServlet
从上面的流程图可以看到前端控制器(中央处理器)DistepcherServlet是SpringMVC核心,查看DistepcherServlet类的继承情况。
UML图:
![2021022601-08-DispatcherServlet UML图](https://gitee.com/chuchq/blogs-gallery/raw/master/images / 2021/2021022601-08-DispatcherServlet UML图.png)
从继承关系看出:
DistepcherServlet ---> FrameworkServlet ---> HttpServletBean---> HttpServlet
那就说明DistepcherServlet 类也是一个Servlet类,那最终核心的方法就是service()方法,即Servlet的核心方法。
那就找service()方法,在DistepcherServlet中没有servic()方法,在父类FrameworkServlet有service()方法,源码如下:
来源:
org.springframework.web.servlet.FrameworkServlet.service(HttpServletRequest request, HttpServletResponse response)
/** * Override the parent class implementation in order to intercept PATCH requests. */ @Override protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { HttpMethod httpMethod = HttpMethod.resolve(request.getMethod()); if (httpMethod == HttpMethod.PATCH || httpMethod == null) { processRequest(request, response); } else { super.service(request, response); } }
可以看到:
FrameworkServlet.service(HttpServletRequest request, HttpServletResponse response)拿到request请求,判断当前请求是否是PATCH请求,不是的就调用父类的servic()方法,掉用父类中的service方法就是去调用该类中doPost(),doGet()方法,根据不同的请求方式然后走doPost()或者doGet(),调用中以doGet()为例,
FrameworkServlet类的doGet()源码:
/** * Delegate GET requests to processRequest/doService. * <p>Will also be invoked by HttpServlet's default implementation of {@code doHead}, * with a {@code NoBodyResponse} that just captures the content length. * @see #doService * @see #doHead */ @Override protected final void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { processRequest(request, response); }
doGet()又调用FrameworkServlet类中的processRequest(request, response);
/** * Process this request, publishing an event regardless of the outcome. * <p>The actual event handling is performed by the abstract * {@link #doService} template method. */ protected final void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { long startTime = System.currentTimeMillis(); Throwable failureCause = null; LocaleContext previousLocaleContext = LocaleContextHolder.getLocaleContext(); LocaleContext localeContext = buildLocaleContext(request); RequestAttributes previousAttributes = RequestContextHolder.getRequestAttributes(); ServletRequestAttributes requestAttributes = buildRequestAttributes(request, response, previousAttributes); WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); asyncManager.registerCallableInterceptor(FrameworkServlet.class.getName(), new RequestBindingInterceptor()); initContextHolders(request, localeContext, requestAttributes); try { doService(request, response); } catch (ServletException | IOException ex) { failureCause = ex; throw ex; } catch (Throwable ex) { failureCause = ex; throw new NestedServletException("Request processing failed", ex); } finally { resetContextHolders(request, previousLocaleContext, previousAttributes); if (requestAttributes != null) { requestAttributes.requestCompleted(); } logResult(request, response, failureCause, asyncManager); publishRequestHandledEvent(request, response, startTime, failureCause); } }
processRequest(request, response)方法中最关键的又调用了doService(request, response);查看FrameworkServlet类中的doService(request, response),或者是调试跟踪可知,doService(request, response)由子类DispatcherServlet实现。
源码来源:
org.springframework.web.servlet.FrameworkServlet.doService(HttpServletRequest request, HttpServletResponse response)
/** * Subclasses must implement this method to do the work of request handling, * receiving a centralized callback for GET, POST, PUT and DELETE. * <p>The contract is essentially the same as that for the commonly overridden * {@code doGet} or {@code doPost} methods of HttpServlet. * <p>This class intercepts calls to ensure that exception handling and * event publication takes place. * @param request current HTTP request * @param response current HTTP response * @throws Exception in case of any kind of processing failure * @see javax.servlet.http.HttpServlet#doGet * @see javax.servlet.http.HttpServlet#doPost */ protected abstract void doService(HttpServletRequest request, HttpServletResponse response) throws Exception;
查看DispatcherServlet中的doService(HttpServletRequest request, HttpServletResponse response)方法
/** * Exposes the DispatcherServlet-specific request attributes and delegates to {@link #doDispatch} * for the actual dispatching. */ @Override protected void doService(HttpServletRequest request, HttpServletResponse response) throws Exception { logRequest(request); // Keep a snapshot of the request attributes in case of an include, // to be able to restore the original attributes after the include. Map<String, Object> attributesSnapshot = null; if (WebUtils.isIncludeRequest(request)) { attributesSnapshot = new HashMap<>(); Enumeration<?> attrNames = request.getAttributeNames(); while (attrNames.hasMoreElements()) { String attrName = (String) attrNames.nextElement(); if (this.cleanupAfterInclude || attrName.startsWith(DEFAULT_STRATEGIES_PREFIX)) { attributesSnapshot.put(attrName, request.getAttribute(attrName)); } } } // Make framework objects available to handlers and view objects. request.setAttribute(WEB_APPLICATION_CONTEXT_ATTRIBUTE, getWebApplicationContext()); request.setAttribute(LOCALE_RESOLVER_ATTRIBUTE, this.localeResolver); request.setAttribute(THEME_RESOLVER_ATTRIBUTE, this.themeResolver); request.setAttribute(THEME_SOURCE_ATTRIBUTE, getThemeSource()); if (this.flashMapManager != null) { FlashMap inputFlashMap = this.flashMapManager.retrieveAndUpdate(request, response); if (inputFlashMap != null) { request.setAttribute(INPUT_FLASH_MAP_ATTRIBUTE, Collections.unmodifiableMap(inputFlashMap)); } request.setAttribute(OUTPUT_FLASH_MAP_ATTRIBUTE, new FlashMap()); request.setAttribute(FLASH_MAP_MANAGER_ATTRIBUTE, this.flashMapManager); } try { doDispatch(request, response); } finally { if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { // Restore the original attribute snapshot, in case of an include. if (attributesSnapshot != null) { restoreAttributesAfterInclude(request, attributesSnapshot); } } } }
DispatcherServlet的doService()方法中最终调用doDispatch(request, response),查看源码如下:
org.springframework.web.servlet.DispatcherServlet.doDispatch()
/** * Process the actual dispatching to the handler. * <p>The handler will be obtained by applying the servlet's HandlerMappings in order. * The HandlerAdapter will be obtained by querying the servlet's installed HandlerAdapters * to find the first that supports the handler class. * <p>All HTTP methods are handled by this method. It's up to HandlerAdapters or handlers * themselves to decide which methods are acceptable. * @param request current HTTP request * @param response current HTTP response * @throws Exception in case of any kind of processing failure */ protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; HandlerExecutionChain mappedHandler = null; boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { ModelAndView mv = null; Exception dispatchException = null; try { // 文件上传相关,判断是不是二进制请求 processedRequest = checkMultipart(request); multipartRequestParsed = (processedRequest != request); // 取得处理当前请求的controller,这里也称为hanlder处理器,第一个步骤的意义就在这里体现了.这里并不是直接返回controller,而是返回的HandlerExecutionChain请求处理器链对象,该对象封装了handler和拦截器interceptors. // Determine handler for the current request. mappedHandler = getHandler(processedRequest); // 如果handler为空,则返回404 if (mappedHandler == null) { noHandlerFound(processedRequest, response); return; } //3. 获取处理request的处理器适配器HandlerAdapter // Determine handler adapter for the current request. HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler()); // Process last-modified header, if supported by the handler. String method = request.getMethod(); boolean isGet = "GET".equals(method); if (isGet || "HEAD".equals(method)) { long lastModified = ha.getLastModified(request, mappedHandler.getHandler()); if (new ServletWebRequest(request, response).checkNotModified(lastModified) && isGet) { return; } } //处理器适配器执行之前,检查拦截器的方法 if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } //处理器适配器根据找到,执行handler,返回ModelAndView // Actually invoke the handler. mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } applyDefaultViewName(processedRequest, mv); mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception ex) { dispatchException = ex; } catch (Throwable err) { // As of 4.3, we're processing Errors thrown from handler methods as well, // making them available for @ExceptionHandler methods and other scenarios. dispatchException = new NestedServletException("Handler dispatch failed", err); } processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException); } catch (Exception ex) { triggerAfterCompletion(processedRequest, response, mappedHandler, ex); } catch (Throwable err) { triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException("Handler processing failed", err)); } finally { if (asyncManager.isConcurrentHandlingStarted()) { // Instead of postHandle and afterCompletion if (mappedHandler != null) { mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response); } } else { // Clean up any resources used by a multipart request. if (multipartRequestParsed) { cleanupMultipart(processedRequest); } } } }
可以看出doDispatch()就是SpringMVC的核心代码了,分析doDispatch():
2.1、查找处理器映射器HandlerMapping
首先看下处理器映射器HandlerMapping类图:
doDispatch()关键代码:
HandlerExecutionChain mappedHandler = null;mappedHandler = getHandler(processedRequest);
mappedHandler是一个执行链HandlerExecutionChain 对象,这里封装了handler和拦截器interceptors,getHandler(processedRequest)方法就是从处理器映射器HandlerMapping中找到url和controller的对应关系,并返回给前端控制器DispatchServlet。
查看getHandler(processedRequest);源码:
/** * Return the HandlerExecutionChain for this request. * <p>Tries all handler mappings in order. * @param request current HTTP request * @return the HandlerExecutionChain, or {@code null} if no handler could be found */ @Nullable protected HandlerExecutionChain getHandler(HttpServletRequest request) throws Exception { if (this.handlerMappings != null) { for (HandlerMapping mapping : this.handlerMappings) { HandlerExecutionChain handler = mapping.getHandler(request); if (handler != null) { return handler; } } } return null; }
调试代码如下:
从代码调试中可以看到handlerMapping中有三个对象:
this.handlerMappings = {ArrayList@4662} size = 3 0 = {BeanNameUrlHandlerMapping@4791} 1 = {RequestMappingHandlerMapping@4792} 2 = {RouterFunctionMapping@4793}
BeanNameUrlHandlerMapping:初始化时会将urlpath做映射存储(
RequestMappingHandlerMapping:初始化时会将Controller中配置@RequestMapping注解的方法做映射存储(注解);
RouterFunctionMapping:
(这个对象不是太理解)
这也就是为什么要去HandlerMapping找一个Handler了,因为处理器映射器HandlerMapping有不同的实现:
1、
2、注解方式
接着看getHandler(HttpServletRequest request)方法,先遍历HandlerMappers,查找控制器找到之后就返回执行链HandlerExecutionChain类型的Handler。
可以看到返回的Handler中,拿到的就是我们自己编码的Controller类,以及拦截器(演示项目中未编写,所以调试汇总返回的Handler最后是0 interceptors)
HandlerExecutionChain with [com.bjpowernode.controller.MyController#doSome()] and 0 interceptors
将正在调试的idea打开自己编写的Controller来对照,发现一致:
2.2、根据处理器映射器HandlerMapping返回结果调用处理器适配器HandlerAdapter
doDispatch()里面的关键代码:
HandlerAdapter ha = getHandlerAdapter(mappedHandler.getHandler());
源码如下:
/** * Return the HandlerAdapter for this handler object. * @param handler the handler object to find an adapter for * @throws ServletException if no HandlerAdapter can be found for the handler. This is a fatal error. */ 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"); }
为什么还要获取处理器适配器HandlerAdapter:与获取处理器映射器HandlerMapping一样,Spring提供了不通的处理器适配器。
调试如下:
查看DEBUG调试模式中getHandlerAdapter()方法在中的:
handler、adapter、this.handlerAdapters
以下是拷贝的结果:
handler
handler = {HandlerMethod@4792} "com.bjpowernode.controller.MyController#doSome()" logger = {LogAdapter$JavaUtilLog@4858} bean = {MyController@4859} beanFactory = {DefaultListableBeanFactory@4847} "org.springframework.beans.factory.support.DefaultListableBeanFactory@56b5a4c3: defining beans [myController,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,org.springframework.web.servlet.view.InternalResourceViewResolver#0]; root of factory hierarchy" beanType = {Class@3782} "class com.bjpowernode.controller.MyController" method = {Method@4860} "public org.springframework.web.servlet.ModelAndView com.bjpowernode.controller.MyController.doSome()" bridgedMethod = {Method@4860} "public org.springframework.web.servlet.ModelAndView com.bjpowernode.controller.MyController.doSome()" parameters = {MethodParameter[0]@4861} responseStatus = null responseStatusReason = null resolvedFromHandlerMethod = {HandlerMethod@4863} "com.bjpowernode.controller.MyController#doSome()" interfaceParameterAnnotations = null description = "com.bjpowernode.controller.MyController#doSome()"
adapter
adapter = {RequestMappingHandlerAdapter@4827} customArgumentResolvers = null argumentResolvers = {HandlerMethodArgumentResolverComposite@4833} initBinderArgumentResolvers = {HandlerMethodArgumentResolverComposite@4834} customReturnValueHandlers = null returnValueHandlers = {HandlerMethodReturnValueHandlerComposite@4835} modelAndViewResolvers = null contentNegotiationManager = {ContentNegotiationManager@4836} messageConverters = {ArrayList@4837} size = 4 requestResponseBodyAdvice = {ArrayList@4838} size = 0 webBindingInitializer = null taskExecutor = {SimpleAsyncTaskExecutor@4839} asyncRequestTimeout = null callableInterceptors = {CallableProcessingInterceptor[0]@4840} deferredResultInterceptors = {DeferredResultProcessingInterceptor[0]@4842} reactiveAdapterRegistry = {ReactiveAdapterRegistry@4844} ignoreDefaultModelOnRedirect = false cacheSecondsForSessionAttributeHandlers = 0 synchronizeOnSession = false sessionAttributeStore = {DefaultSessionAttributeStore@4845} parameterNameDiscoverer = {DefaultParameterNameDiscoverer@4846} beanFactory = {DefaultListableBeanFactory@4847} "org.springframework.beans.factory.support.DefaultListableBeanFactory@56b5a4c3: defining beans [myController,org.springframework.context.annotation.internalConfigurationAnnotationProcessor,org.springframework.context.annotation.internalAutowiredAnnotationProcessor,org.springframework.context.annotation.internalCommonAnnotationProcessor,org.springframework.context.event.internalEventListenerProcessor,org.springframework.context.event.internalEventListenerFactory,org.springframework.web.servlet.view.InternalResourceViewResolver#0]; root of factory hierarchy" sessionAttributesHandlerCache = {ConcurrentHashMap@4848} size = 0 initBinderCache = {ConcurrentHashMap@4849} size = 0 initBinderAdviceCache = {LinkedHashMap@4850} size = 0 modelAttributeCache = {ConcurrentHashMap@4851} size = 0 modelAttributeAdviceCache = {LinkedHashMap@4852} size = 0 order = 2147483647 supportedMethods = null allowHeader = "GET,HEAD,POST,PUT,PATCH,DELETE,OPTIONS" requireSession = false cacheControl = null cacheSeconds = -1 varyByRequestHeaders = null useExpiresHeader = false useCacheControlHeader = true useCacheControlNoStore = true alwaysMustRevalidate = false servletContext = {ApplicationContextFacade@4754} logger = {LogAdapter$JavaUtilLog@4854} applicationContext = {
this.handlerAdapters
this.handlerAdapters = {ArrayList@4658} size = 4 0 = {HttpRequestHandlerAdapter@4810} 1 = {SimpleControllerHandlerAdapter@4820} //
可以看到找到4个处理器适配器。通过DEBUG模式可以看到,此次取到的处理器适配器HandlerAdapter是:RequestMappingHandlerAdapter
ha = {RequestMappingHandlerAdapter@4827}
2.3、检查拦截器Interceptor
doDispatch()中的关键代码:
if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; }org.springframework.web.servlet.HandlerExecutionChain#applyPreHandle
applyPreHandle(processedRequest, response)源码:
/** * Apply preHandle methods of registered interceptors. * @return {@code true} if the execution chain should proceed with the * next interceptor or the handler itself. Else, DispatcherServlet assumes * that this interceptor has already dealt with the response itself. */ boolean applyPreHandle(HttpServletRequest request, HttpServletResponse response) throws Exception { HandlerInterceptor[] interceptors = getInterceptors(); if (!ObjectUtils.isEmpty(interceptors)) { for (int i = 0; i < interceptors.length; i++) { HandlerInterceptor interceptor = interceptors[i]; if (!interceptor.preHandle(request, response, this.handler)) { triggerAfterCompletion(request, response, null); return false; } this.interceptorIndex = i; } } return true; }
2.3、处理器适配器HandlerAdapter执行Handler(Controller)返回ModelAndView
doDispatch()中的关键代码:
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
DEBUG模式调试,是跳到了:
org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter#handle
源码如下:
/** * This implementation expects the handler to be an {@link HandlerMethod}. */ @Override @Nullable public final ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { return handleInternal(request, response, (HandlerMethod) handler); }
再往下看handleInternal(request, response, (HandlerMethod) handler)方法,
org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter#handleInternal
@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; }
注意,handleInternal(request, response, (HandlerMethod) handler)方法的返回值是ModelAndView ,这里就完成了处理器适配器HandlerAdapter执行Handler(Controller)并将结果ModelAndView返回给前端控制器DistepchServlet
2.4、视图解析器ViewResolver
接上2.3:前端控制器DistepchServlet接收到处理器适配器HandlerAdapter返回的ModelAndView以后,这里分2种情况:
- (1)、如果ModelAndView里面是逻辑视图
前端控制器DistepchServlet调用视图解析器ViewResolver通过逻辑视图查找真正的视图对象View,并返回给前端控制器DistepchServlet。 - (2)、如果ModelAndView里面是非逻辑视图:
如:MappingJackson2JsonView(把当前数据转为为JSON数据,并不需要对视图逻辑名称进行转换)
总结一下:
视图解析器ViewResolver接口主要作用是解析前端控制器DispatcherServlet传递的逻辑视图名,并将解析结果的真正的视图对象View传回给前端控制器DispatcherServlet
ViewResolverd的实现类:
ViewResolver的UML:
2.5、视图View
2.5.1、视图对象的作用
- (1)、将控制器返回的数据处理渲染,最终返回客户端展示给用户,主要就是完成转发或者是重定向的操作.。
- (2)、为了实现视图模型和具体实现技术的解耦(指的是Spring在org.springframework.web.servlet包中定义的抽象View接口),详见2.5.2View接口图。
- (3)、视图对象View由视图解析器负责实例化。由于视图是无状态(每一次请求都会创建一个新的view对象)的,所以不会有线程安全的问题.
2.5.2、View接口图
2.5.3、View的实现类图
2.5.4、View的UML图
![2021022601-20-01-View-uml(hierarchic group layout)](https://gitee.com/chuchq/blogs-gallery/raw/master/images / 2021/2021022601-20-01-View-uml(hierarchic group layout).png)
2.5.5、常用的View视图类
视图类型 | 简介 |
URL视图资源图 | InternalResourceView | 将JSP或其他资源封装成一个视图。被视图解析器InternalResourceViewResolver默认使用。 |
JstlView | InternalResourceView的子类。如果JSP中使用了JSTL的国际化标签,就需要使用该视图类。 |
文档视图 | AbstractExcelView | Excel文档视图的抽象类。 |
AbstractPdfView | PDF文档视图的抽象类 |
报表视图 | ConfigurableJasperReportsView | 常用的JasperReports报表视图 |
JasperReportsHtmlView |
JasperReportsPdfView |
JasperReportsXlsView |
JSON视图 | MappingJackson2JsonView | 将数据通过Jackson框架的ObjectMapper对象,以JSON方式输出 |
2.6、其他重要的点
2.6.1、DispatcherServlet.properties
DispatcherServlet.properties文件是在SpringMVC架包中:
DispatcherServlet.properties内容:
# Default implementation classes for DispatcherServlet's strategy interfaces.# Used as fallback when no matching beans are found in the DispatcherServlet context.# Not meant to be customized by application developers.org.springframework.web.servlet.LocaleResolver= org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolverorg.springframework.web.servlet.ThemeResolver= org.springframework.web.servlet.theme.FixedThemeResolverorg.springframework.web.servlet.HandlerMapping= org.springframework.web.servlet.handler.BeanNameUrlHandlerMapping,\ org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping,\ org.springframework.web.servlet.function.support.RouterFunctionMappingorg.springframework.web.servlet.HandlerAdapter= org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter,\ org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter,\ org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter,\ org.springframework.web.servlet.function.support.HandlerFunctionAdapterorg.springframework.web.servlet.HandlerExceptionResolver= org.springframework.web.servlet.mvc.method.annotation.ExceptionHandlerExceptionResolver,\ org.springframework.web.servlet.mvc.annotation.ResponseStatusExceptionResolver,\ org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolverorg.springframework.web.servlet.RequestToViewNameTranslator= org.springframework.web.servlet.view.DefaultRequestToViewNameTranslatororg.springframework.web.servlet.ViewResolver= org.springframework.web.servlet.view.InternalResourceViewResolverorg.springframework.web.servlet.FlashMapManager= org.springframework.web.servlet.support.SessionFlashMapManager
SpringMVC为什么能加载不同处理器映射器HandlerMapping、处理器适配器handlerAdapter,就是因为框架配置了这个DispatcherServlet.properties文件。
三、引用参考资料
1、引用资料
SpringMVC流程图引用地址:https://www.iqiyi.com/w_19s2gmyazh.html
SpringMVC流程图引用地址2:https://blog.csdn.net/win7system/article/details/90674757
View视图作用引用地址:https://blog.csdn.net/qq_43193797/article/details/84928603
Spring官方文档:https://spring.io/projects/spring-framework#learn/
在写此文的时候可能还有少部分是参考了其他资料,但是整理的时候我已经找不到原文出处了,如果原文作者看到,请及时联系我,我在文章中加上引用出处,谢谢!
2、参考资料
参考:w3cschool-Spring MVC 4.2.4.RELEASE 中文文档:
https://www.w3cschool.cn/spring_mvc_documentation_linesh_translation/
参考:https://www.cnblogs.com/leftthen/category/790002.html
免责声明:
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