[闹着玩-2]spring-mvc 主要流程

SpringMvc【源码仓库】【本文仓库】三层结构表现层MVC模型业务层service持久层dao工作流程用户->前端控制器:用户发送请求前端控制器-> 后端控制器:根据用户请求查询具体控制器后端控制器–>前端控制器:处理后结果前端控制器–> 视图:视图渲染视图–>前端控制器:返回视图前端控制器–> 用户:响应结果简单案例依赖<?xml version=“1.0” encoding=“UTF-8”?><project xmlns=“http://maven.apache.org/POM/4.0.0" xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=“http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.huifer</groupId> <artifactId>mySpringMvcBook</artifactId> <version>1.0-SNAPSHOT</version> <packaging>war</packaging> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> <spring.version>5.1.5.RELEASE</spring.version> <junit.version>4.12</junit.version> </properties><dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-expression</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aspects</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>aopalliance</groupId> <artifactId>aopalliance</artifactId> <version>1.0</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-web</artifactId> <version>${spring.version}</version> </dependency> <!– https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl –> <dependency> <groupId>javax.servlet.jsp.jstl</groupId> <artifactId>jstl</artifactId> <version>1.2</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>servlet-api</artifactId> <version>2.5</version> </dependency> <dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.18.4</version> </dependency> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-databind</artifactId> <version>2.9.3</version> </dependency> <!– https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core –> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-core</artifactId> <version>2.9.3</version> </dependency> <!– https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations –> <dependency> <groupId>com.fasterxml.jackson.core</groupId> <artifactId>jackson-annotations</artifactId> <version>2.9.3</version> </dependency></dependencies> <build> <resources> <!–千千万万别忘记–> <resource> <directory>src/main/java</directory> <includes> <include>**/.xml</include> </includes> </resource> </resources> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <configuration> <source>1.8</source> <target>1.8</target> <encoding>UTF-8</encoding> </configuration> </plugin> </plugins> </build></project>spring-config<?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:mvc=“http://www.springframework.org/schema/mvc" xsi:schemaLocation=“http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd"> <context:component-scan base-package=“com.huifer.springmvc”/> <!– 配置注解的适配器和映射器，同时还注入了很多其他的bean –> <mvc:annotation-driven/></beans>web.xml<?xml version=“1.0” encoding=“UTF-8”?><web-app xmlns=“http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=“http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd" version=“4.0”> <servlet> <servlet-name>springmvc</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring-mvc-config.xml</param-value> </init-param> <!–跟随tomcat启动–> <load-on-startup>2</load-on-startup> </servlet> <servlet-mapping> <servlet-name>springmvc</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping></web-app>controller@Controller@RequestMapping(“item”)public class ItemController { @ResponseBody @GetMapping("/query”) public ModelAndView query() throws Exception { List<Item> itemList = new ArrayList<>(); itemList.add(new Item(“吃的”, 3.3, new Date())); itemList.add(new Item(“玩的”, 3.3, new Date())); ModelAndView modelAndView = new ModelAndView(); modelAndView.addObject(“itemList”, itemList); modelAndView.setViewName("/WEB-INF/jsp/item.jsp”); return modelAndView; }}item.JSP<%– Created by IntelliJ IDEA. User: huifer Date: 2019/3/10 Time: 11:26 To change this template use File | Settings | File Templates.–%><%@ page language=“java” contentType=“text/html; charset=UTF-8” pageEncoding=“UTF-8” isELIgnored=“false” %><!DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN” “http://www.w3.org/TR/html4/loose.dtd"><html><head> <title>ItemList</title></head><body><h1>ITEM</h1><p>${itemList}</p></body></html>web.xml 中的加载顺序context-param->listener->filter->servleturl-parttern 匹配顺序精确匹配 ，如/baidu目录匹配，如/拓展名匹配，如.jpg默认匹配 ，如/tomcat中的url-parttern文件在 ${tomcatHome}/conf/web.xml中发布到tomcat的web应用共享下面两个配置 <!– The mapping for the default servlet –> <servlet-mapping> <servlet-name>default</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> <!– The mappings for the JSP servlet –> <servlet-mapping> <servlet-name>jsp</servlet-name> <url-pattern>.jsp</url-pattern> <url-pattern>.jspx</url-pattern> </servlet-mapping>此处面试题为什么在自己的项目中web.xml配置/ 报错。如图根据tomcat的web.xml配置可以看到 / 和jsp的拦截是分开的 ，而我们直接用一个/*来拦截那么tomcat将不知道用什么来处理spring-mvc大致流程源码翻阅从配置文件中知道前端控制器DispatcherServlet<servlet> <servlet-name>springmvc</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:spring-mvc-config.xml</param-value> </init-param> <!–跟随tomcat启动–> <load-on-startup>2</load-on-startup></servlet>在org.springframework.web.servlet.DispatcherServlet 看下面两个方法doService 将访问的数据接收到交给doDispatchdoDispatch 具体调度protected void doDispatch(HttpServletRequest request, HttpServletResponse response) throws Exception { HttpServletRequest processedRequest = request; HandlerExecutionChain mappedHandler = null; boolean multipartRequestParsed = false; WebAsyncManager asyncManager = WebAsyncUtils.getAsyncManager(request); try { try { ModelAndView mv = null; Object dispatchException = null; try { processedRequest = this.checkMultipart(request); multipartRequestParsed = processedRequest != request; // 加载handler mappedHandler = this.getHandler(processedRequest); if (mappedHandler == null) { this.noHandlerFound(processedRequest, response); return; } // handler适配器 HandlerAdapter ha = this.getHandlerAdapter(mappedHandler.getHandler()); 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; } } if (!mappedHandler.applyPreHandle(processedRequest, response)) { return; } // 适配器执行操作 mv = ha.handle(processedRequest, response, mappedHandler.getHandler()); if (asyncManager.isConcurrentHandlingStarted()) { return; } this.applyDefaultViewName(processedRequest, mv); mappedHandler.applyPostHandle(processedRequest, response, mv); } catch (Exception var20) { dispatchException = var20; } catch (Throwable var21) { dispatchException = new NestedServletException(“Handler dispatch failed”, var21); } // 操作结果返回 this.processDispatchResult(processedRequest, response, mappedHandler, mv, (Exception)dispatchException); } catch (Exception var22) { this.triggerAfterCompletion(processedRequest, response, mappedHandler, var22); } catch (Throwable var23) { this.triggerAfterCompletion(processedRequest, response, mappedHandler, new NestedServletException(“Handler processing failed”, var23)); } } finally { if (asyncManager.isConcurrentHandlingStarted()) { if (mappedHandler != null) { mappedHandler.applyAfterConcurrentHandlingStarted(processedRequest, response); } } else if (multipartRequestParsed) { this.cleanupMultipart(processedRequest); } } }handler怎么来initHandlerMappings(context)protected void initStrategies(ApplicationContext context) { this.initMultipartResolver(context); this.initLocaleResolver(context); this.initThemeResolver(context); this.initHandlerMappings(context); this.initHandlerAdapters(context); this.initHandlerExceptionResolvers(context); this.initRequestToViewNameTranslator(context); this.initViewResolvers(context); this.initFlashMapManager(context); } 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(matchingBeans.values()); AnnotationAwareOrderComparator.sort(this.handlerMappings); } } else { try { HandlerMapping hm = (HandlerMapping)context.getBean(“handlerMapping”, HandlerMapping.class); this.handlerMappings = Collections.singletonList(hm); } catch (NoSuchBeanDefinitionException var3) { } } if (this.handlerMappings == null) { // 读取默认配置文件 this.handlerMappings = this.getDefaultStrategies(context, HandlerMapping.class); if (this.logger.isTraceEnabled()) { this.logger.trace(“No HandlerMappings declared for servlet ‘” + this.getServletName() + “’: using default strategies from DispatcherServlet.properties”); } } }默认配置文件handler适配器也在配置文件中 protected HandlerAdapter getHandlerAdapter(Object handler) throws ServletException { if (this.handlerAdapters != null) { Iterator var2 = this.handlerAdapters.iterator(); while(var2.hasNext()) { HandlerAdapter adapter = (HandlerAdapter)var2.next(); // 是否能够适配 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”); }HttpRequestHandlerAdapterpublic class HttpRequestHandlerAdapter implements HandlerAdapter { public HttpRequestHandlerAdapter() { }// 判断是否是当前类支持的适配器 public boolean supports(Object handler) { return handler instanceof HttpRequestHandler; }// 适配器执行操作 @Nullable public ModelAndView handle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { ((HttpRequestHandler)handler).handleRequest(request, response); return null; } public long getLastModified(HttpServletRequest request, Object handler) { return handler instanceof LastModified ? ((LastModified)handler).getLastModified(request) : -1L; }}视图解析 private void processDispatchResult(HttpServletRequest request, HttpServletResponse response, @Nullable HandlerExecutionChain mappedHandler, @Nullable ModelAndView mv, @Nullable Exception exception) throws Exception { boolean errorView = false; if (exception != null) { if (exception instanceof ModelAndViewDefiningException) { this.logger.debug(“ModelAndViewDefiningException encountered”, exception); mv = ((ModelAndViewDefiningException)exception).getModelAndView(); } else { Object handler = mappedHandler != null ? mappedHandler.getHandler() : null; mv = this.processHandlerException(request, response, handler, exception); errorView = mv != null; } } if (mv != null && !mv.wasCleared()) { // 这个地方在做渲染 this.render(mv, request, response); if (errorView) { WebUtils.clearErrorRequestAttributes(request); } } else if (this.logger.isTraceEnabled()) { this.logger.trace(“No view rendering, null ModelAndView returned.”); } if (!WebAsyncUtils.getAsyncManager(request).isConcurrentHandlingStarted()) { if (mappedHandler != null) { mappedHandler.triggerAfterCompletion(request, response, (Exception)null); } } }protected void render(ModelAndView mv, HttpServletRequest request, HttpServletResponse response) throws Exception { Locale locale = this.localeResolver != null ? this.localeResolver.resolveLocale(request) : request.getLocale(); response.setLocale(locale); String viewName = mv.getViewName(); View view; if (viewName != null) { // 视图解析器 view = this.resolveViewName(viewName, mv.getModelInternal(), locale, request); if (view == null) { throw new ServletException(“Could not resolve view with name ‘” + mv.getViewName() + “’ in servlet with name ‘” + this.getServletName() + “’”); } } else { view = mv.getView(); if (view == null) { throw new ServletException(“ModelAndView [” + mv + “] neither contains a view name nor a View object in servlet with name ‘” + this.getServletName() + “’”); } } if (this.logger.isTraceEnabled()) { this.logger.trace(“Rendering view [” + view + “] “); } try { if (mv.getStatus() != null) { response.setStatus(mv.getStatus().value()); } // 视图的渲染函数渲染到页面上 view.render(mv.getModelInternal(), request, response); } catch (Exception var8) { if (this.logger.isDebugEnabled()) { this.logger.debug(“Error rendering view [” + view + “]”, var8); } throw var8; } }@Nullableprotected View resolveViewName(String viewName, @Nullable Map<String, Object> model, Locale locale, HttpServletRequest request) throws Exception { if (this.viewResolvers != null) { Iterator var5 = this.viewResolvers.iterator(); while(var5.hasNext()) { // 视图解析器 ViewResolver viewResolver = (ViewResolver)var5.next(); View view = viewResolver.resolveViewName(viewName, locale); if (view != null) { return view; } } } return null;}spring-mvc请求具体流程图用户->前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:1.用户发送请求 前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 -> HandlerMapper : 2.根据url进行处理HandlerMapper -> 前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:3.将handlerMapper处理结果给前端控制器前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果-> HandlerAdapter:4.给适配器确认具体的适配器，比如我们这里给了HttpRequestHandlerAdapterHandlerAdapter ->ModelAndView:5.用来执行业务操作ModelAndView ->HandlerAdapter: 6.执行完成给HandlerAdapter返回HandlerAdapter->前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:7.返回一个modelAndView前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果-> ViewResolver 视图解析器 :8.将第7步中的view进行解析ViewResolver 视图解析器->前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果:9.解析结果返回前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 -> View : 9.将model渲染到view中View->前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果: 10.view 结果返回给前端控制器前端控制器\n org.springframework.web.servlet.DispatcherServlet\n 用来接收响应以及返回响应结果 –> 用户:查看到完整的网页