什么是Spring MVC?
Spring MVC 为展现层提供的基于 MVC 设计理念的优秀的Web 框架，是目前最主流的 MVC 框架之一。
Spring3.0 后全面超越 Struts2，成为最优秀的 MVC 框架

Spring Web MVC处理请求的流程

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Spring Web MVC架构

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导入jar包
我们基于Spring mvc框架进行开发，需要依赖一下的spring jar包：
在WEB-INF目录下新建lib文件夹，并将上面的jar包放入其中。
配置文件web.xml（WEB-INF下）

pom.xml文件如下↓↓↓↓

<?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.neuedu</groupId>
  <artifactId>springMVC</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>war</packaging>

  <name>springMVC Maven Webapp</name>
  <!-- FIXME change it to the project's website -->
  <url>http://www.example.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>1.7</maven.compiler.source>
    <maven.compiler.target>1.7</maven.compiler.target>
    <springFramework.version>5.1.5.RELEASE</springFramework.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>4.11</version>
      <scope>test</scope>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>${springFramework.version}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>${springFramework.version}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>${springFramework.version}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-jdbc</artifactId>
      <version>${springFramework.version}</version>
    </dependency>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-test</artifactId>
      <version>${springFramework.version}</version>
    </dependency>
    <dependency>
      <groupId>log4j</groupId>
      <artifactId>log4j</artifactId>
      <version>1.2.17</version>
    </dependency>
    <dependency>
      <groupId>commons-logging</groupId>
      <artifactId>commons-logging</artifactId>
      <version>1.2</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-databind -->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.9.8</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-core -->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
      <version>2.9.8</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.core/jackson-annotations -->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-annotations</artifactId>
      <version>2.9.8</version>
    </dependency>

  </dependencies>

  <build>
    <finalName>springMVC</finalName>
    <pluginManagement><!-- lock down plugins versions to avoid using Maven defaults (may be moved to parent pom) -->
      <plugins>
        <plugin>
          <artifactId>maven-clean-plugin</artifactId>
          <version>3.1.0</version>
        </plugin>
        <!-- see http://maven.apache.org/ref/current/maven-core/default-bindings.html#Plugin_bindings_for_war_packaging -->
        <plugin>
          <artifactId>maven-resources-plugin</artifactId>
          <version>3.0.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.8.0</version>
        </plugin>
        <plugin>
          <artifactId>maven-surefire-plugin</artifactId>
          <version>2.22.1</version>
        </plugin>
        <plugin>
          <artifactId>maven-war-plugin</artifactId>
          <version>3.2.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-install-plugin</artifactId>
          <version>2.5.2</version>
        </plugin>
        <plugin>
          <artifactId>maven-deploy-plugin</artifactId>
          <version>2.8.2</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xmlns="http://xmlns.jcp.org/xml/ns/javaee" 
xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" 
id="WebApp_ID" version="3.1"> 
    <!-- 配置DispatchcerServlet前端控制器，请求集合点 -->
    <servlet>
        <servlet-name>springDispatcherServlet</servlet-name>
         <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
         <!-- 配置Spring mvc下的配置文件的位置和名称 -->
         <init-param>
             <param-name>contextConfigLocation</param-name>
             <param-value>classpath:springmvc.xml</param-value>
         </init-param>
         <load-on-startup>1</load-on-startup>
     </servlet>
     <servlet-mapping>
         <servlet-name>springDispatcherServlet</servlet-name>
         <url-pattern>/</url-pattern>
     </servlet-mapping>
</web-app>

注意： <param-value>classpath:springmvc.xml</param-value>用于配置spring mvc的配置文件的位置和名称，这里说明会新建一个springmvc.xml的配置文件。

这里的servlet-mapping表示拦截的模式，这里是“/”，表示对于非jsp请求进行拦截。

Springmvc.xml（scr下）
在src目录下新建springmvc.xml

<?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-4.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd">
        <!-- 配置自动扫描的包 -->
        <context:component-scan base-package="com.neusoft.controller"></context:component-scan>
        <!-- 配置视图解析器 如何把handler 方法返回值解析为实际的物理视图 -->
        <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
            <property name = "prefix" value="/WEB-INF/views/"></property>
            <property name = "suffix" value = ".jsp"></property>
        </bean>
</beans>

<context:component-scan base-package="com.neusoft.controller"></context:component-scan>
表示spring监听的范围，这里是在com.neusoft.controller下

HelloWorldController.java（com.neusoft.controller下)

@Controller层原servlet层

package com.neuedu.web;

import com.neuedu.pojo.Student;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.ModelAndView;

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

@Controller
//@RestController是可以直接返回json的注解
@RequestMapping("user")
public class HelloController {
//    第一种方式，注解直接接post和get，在注解的括号里面写接的请求方式
    @RequestMapping(value = "add",method = RequestMethod.GET)
    public void hello1(){
        System.out.println("hello springmvc add");
    }
//    注解直接可以该成getmapping就是接get请求
    @GetMapping("del")
    public void hello2(){
        System.out.println("hello springmvc del");
    }
    //    注解直接可以该成postmapping就是接post请求
//    并且接请求的方式为在方法的括号中写requestparam（接的名字）类型 形参
    @PostMapping("select")
    public void hello3(@RequestParam("username") String name){
        System.out.println("hello springmvc select"+name);
    }
//    接的是post请求，传过来的直接封装到student里，前提是student的属性和前台传过来的名字一样
    @PostMapping("select2")
    public void hello3(Student student){
        System.out.println("hello springmvc select"+student);
    }
//    接的是session的时候可以直接在方法的括号里面写httpsession 就可以获取session
    @PostMapping("select3")
    public void hello4(Student student,HttpSession session){
        System.out.println("hello springmvc select"+student);
    }



//    下面讲返回值
    /**
     * 返回值类型
     *      void -- 响应ajax请求，response.getwriter（）.print（）
     *      String  --可以转发和重定向
     *      ModelAndView -- 只能做转发
     *
     */
    @GetMapping("select4")
    
    public String hello5(Student student, Model model){
//    如果姓名是mike，跳转到success.jsp
        if(student.getUsername().equals("mike")){
//            return "/success.jsp";
//            下面这个是往request里放数据
            model.addAttribute("username","mike");
            return "forward:/success.jsp";//forward也可以不写，默认的就是forward
        }else{
            //        否则跳转失败页面
            return "redirect:/fail.jsp";
        }

    }

    public ModelAndView hello6(Student student, Model model){
        ModelAndView modelAndView = new ModelAndView();

//    如果姓名是mike，跳转到success.jsp
        if(student.getUsername().equals("mike")){
//            return "/success.jsp";
//            下面这个是往request里放数据
            modelAndView.addObject("userinfo","mike000");
            modelAndView.setViewName("success");
        }else{
            //        否则跳转失败页面
            modelAndView.setViewName("fail");
        }
        return modelAndView;
    }
    @GetMapping("serch")
    
    public  void serch(@RequestParam("id") Integer id, HttpServletResponse response){

    }
    @GetMapping("serch")
    //    @ResponseBody
    public  Student serch1(@RequestParam("id") Integer id, HttpServletResponse response){
        Student student = new Student();
        return student;
    }
}