Spring 学习教程（三）：Spring MVC

在springmvc中 @RequestMapping(value={"list", ""})表示的意思

@RequestMapping是请求路径的注解

里面写两个value就是,路径可以是这两个,

第二个空,是路径可以为空, 比如www.baidu.com/list和www.baidu.com , 都可以访问这个方法

1. 用户访问 /index
2. 根据web.xml中的配置 所有的访问都会经过DispatcherServlet
3. 根据 根据配置文件springmvc-servlet.xml ，访问路径/index
会进入IndexController类
4. 在IndexController中指定跳转到页面index.jsp，并传递message数据
5. 在index.jsp中显示message信息

二， 跳转 ：

如果代码写成这样，就表示跳转到页面 index.jsp 
new ModelAndView("index.jsp"); 

所谓的视图定位，指的是代码还是写成这样，但是会跳转到 /WEB-INF/page/index.jsp 
new ModelAndView("index");

springmvc-servlet.xml 如下：

<?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-3.0.xsd
http://www.springframework.org/schema/context 
http://www.springframework.org/schema/context/spring-context-3.0.xsd 
http://www.springframework.org/schema/mvc 
http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

<context:component-scan base-package="controller" />
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="prefix" value="/" />
<property name="suffix" value=".jsp" />
</bean>

<!-- 文件上传 -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"/>
<!-- <bean id="simpleUrlHandlerMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
<property name="mappings">
<props>
<prop key="/index">indexController</prop>
</props>
</property>
</bean>
<bean id="indexController" class="controller.IndexController"></bean> -->


<mvc:interceptors> 
<mvc:interceptor> 
<mvc:mapping path="/index"/> 
<!-- 定义在mvc:interceptor下面的表示是对特定的请求才进行拦截的 --> 
<bean class="interceptor.IndexInterceptor"/> 
</mvc:interceptor> 
<!-- 当设置多个拦截器时，先按顺序调用preHandle方法，然后逆序调用每个拦截器的postHandle和afterCompletion方法 --> 
</mvc:interceptors>

</beans

IndexController.java  如下：

package controller;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class IndexController  {
 
    @RequestMapping("/index")
    public ModelAndView index(HttpServletRequest request,HttpServletResponse response) throws Exception {
        ModelAndView mav = new ModelAndView("index");
        mav.addObject("message", "Hello Spring MVC");
        return mav;
    }
    
     @RequestMapping("/jump")
     public ModelAndView jump() {
        ModelAndView mav = new ModelAndView("redirect:/index");//即表示客户端跳转的意思,跳转index方法
        return mav;
     }
     
     @RequestMapping("/check")
     public ModelAndView check(HttpSession session) {
        Integer i = (Integer) session.getAttribute("count");
        if (i == null)
            i = 0;
        i++;
        session.setAttribute("count", i);
        ModelAndView mav = new ModelAndView("check");
        return mav;
    }
}

IndexInterceptor.java

package interceptor;

import java.util.Date;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class IndexInterceptor extends HandlerInterceptorAdapter {

    /** 
     * 在DispatcherServlet完全处理完请求后被调用,可用于清理资源等  
     * 当有拦截器抛出异常时,会从当前拦截器往回执行所有的拦截器的afterCompletion() 
     */
    @Override
    public void afterCompletion(HttpServletRequest request,
            HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println("afterCompletion(), 在访问视图之后被调用"); 
    }

    /**
     * 在业务处理器处理请求执行完成后,生成视图之前执行的动作   
     * 可在modelAndView中加入数据，比如当前时间
     */ 
    @Override
    public void postHandle(HttpServletRequest request,
            HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
         System.out.println("postHandle(), 在访问Controller之后，访问视图之前被调用,这里可以注入一个时间到modelAndView中，用于后续视图显示");
         modelAndView.addObject("date","由拦截器生成的时间:" + new Date());
    }

    /** 
     * 在业务处理器处理请求之前被调用 
     * 如果返回false 
     *     从当前的拦截器往回执行所有拦截器的afterCompletion(),再退出拦截器链
     * 如果返回true 
     *    执行下一个拦截器,直到所有的拦截器都执行完毕 
     *    再执行被拦截的Controller 
     *    然后进入拦截器链, 
     *    从最后一个拦截器往回执行所有的postHandle() 
     *    接着再从最后一个拦截器往回执行所有的afterCompletion() 
     */   
    @Override
    public boolean preHandle(HttpServletRequest request,
            HttpServletResponse response, Object handler) throws Exception {
         System.out.println("preHandle(), 在访问Controller之前被调用"); 
         return true;
    }

 
}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" version="2.5">
  <display-name>SpringMVC02</display-name>

  <servlet-mapping>
        <servlet-name>default</servlet-name>
        <url-pattern>*.jpg</url-pattern>
    </servlet-mapping>
  
  <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>
            org.springframework.web.servlet.DispatcherServlet
        </servlet-class>
        <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
  </servlet-mapping>
  
    <!-- 处理post提交中文乱码 -->
    <filter> 
        <filter-name>CharacterEncodingFilter</filter-name> 
        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> 
        <init-param> 
            <param-name>encoding</param-name> 
            <param-value>utf-8</param-value> 
        </init-param> 
    </filter> 
    <filter-mapping> 
        <filter-name>CharacterEncodingFilter</filter-name> 
        <url-pattern>/*</url-pattern> 
    </filter-mapping>  
    
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
    
</web-app>

index.jsp

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Insert title here</title>
</head>
<body>
<h1>${message}</h1>
<p>${date}</p>
</body>
</html>

参考：https://blog.csdn.net/qq_33530388/article/details/72784199

http://how2j.cn/k/springmvc/springmvc-springmvc/615.html