[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

    4.0.0

    com.huifer
    mySpringMvcBook
    1.0-SNAPSHOT

    war

    
        UTF-8
        UTF-8
        1.8
        5.1.5.RELEASE
        4.12
    


    
        org.springframework
        spring-beans
        ${spring.version}
    
    
        org.springframework
        spring-core
        ${spring.version}
    
    
        org.springframework
        spring-context
        ${spring.version}
    
    
        org.springframework
        spring-expression
        ${spring.version}
    

    
        org.springframework
        spring-aspects
        ${spring.version}
    
    
        aopalliance
        aopalliance
        1.0
    

    
        org.springframework
        spring-webmvc
        ${spring.version}
    
    
        org.springframework
        spring-web
        ${spring.version}
    


    
    
        javax.servlet.jsp.jstl
        jstl
        1.2
    
    
        javax.servlet
        servlet-api
        2.5
    
    
        org.projectlombok
        lombok
        1.18.4
    
    
        com.fasterxml.jackson.core
        jackson-databind
        2.9.3
    
    
    
        com.fasterxml.jackson.core
        jackson-core
        2.9.3
    
    
    
        com.fasterxml.jackson.core
        jackson-annotations
        2.9.3
    


    
        
            
            
                src/main/java
                
                    **/*.xml
                
            
        
        
            
                org.apache.maven.plugins
                maven-compiler-plugin
                
                    1.8
                    1.8
                    UTF-8
                
            
        
    

spring-config

web.xml

    
        springmvc
        org.springframework.web.servlet.DispatcherServlet
        
            contextConfigLocation
            classpath:spring-mvc-config.xml
        
        
        2

    
    
        springmvc
        /
    

• controller

  @Controller
  @RequestMapping("item")
  public class ItemController {
      @ResponseBody
      @GetMapping("/query")
      public ModelAndView query() throws Exception {
  
          List 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" %>
  
  
  
      
  
  
  ITEM
  ${itemList}
  
  

web.xml 中的加载顺序

context-param->listener->filter->servlet

url-parttern 匹配顺序

1. 精确匹配 ，如/baidu
2. 目录匹配，如/*
3. 拓展名匹配，如*.jpg
4. 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

     
      
          default
          /
      
  
      
      
          jsp
          *.jsp
          *.jspx
      

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

    springmvc
    org.springframework.web.servlet.DispatcherServlet
    
        contextConfigLocation
        classpath:spring-mvc-config.xml
    
    
    2

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doDispatch
• doDispatch 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 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");
      }

  • HttpRequestHandlerAdapter

    public 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;
          }
      }

  @Nullable
  protected View resolveViewName(String viewName, @Nullable Map 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HttpRequestHandlerAdapter
HandlerAdapter ->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