接上一篇：SpringMVC接收请求参数

1. 跳转

1.1 pom.xml中导入依赖：jstl，jsp-api,servlet-api

<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>4.0.0modelVersion>

    <groupId>org.examplegroupId>
    <artifactId>springMVC03artifactId>
    <version>1.0-SNAPSHOTversion>
    <packaging>warpackaging>
    <dependencies>
        <dependency>
            <groupId>org.springframeworkgroupId>
            <artifactId>spring-webmvcartifactId>
            <version>5.3.16version>
        dependency>
        <dependency>
            <groupId>javax.servlet.jsp.jstlgroupId>
            <artifactId>jstlartifactId>
            <version>1.2version>
        dependency>
        <dependency>
            <groupId>javax.servletgroupId>
            <artifactId>javax.servlet-apiartifactId>
            <version>3.1.0version>
        dependency>
        <dependency>
            <groupId>javax.servletgroupId>
            <artifactId>jsp-apiartifactId>
            <version>2.0version>
        dependency>
    dependencies>
    <build>
        <resources>
            <resource>
                <directory>src/main/javadirectory>
                <includes>
                    <include>*.xmlinclude>
                    <include>**/*.xmlinclude>
                includes>
                <filtering>truefiltering>
            resource>
        resources>
    build>

project>

1.2 视图解析器ViewResolver

<beans xmlns=\"http://www.springframework.org/schema/beans\"
       xmlns:context=\"http://www.springframework.org/schema/context\"
       xmlns:mvc=\"http://www.springframework.org/schema/mvc\"
       xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\"
       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.lyx\"/>

    <mvc:annotation-driven>mvc:annotation-driven>

    <bean class=\"org.springframework.web.servlet.view.InternalResourceViewResolver\">
        <property name=\"prefix\" value=\"/\"/>
        <property name=\"suffix\" value=\".jsp\"/>
    bean>
beans>

1.3 代码

后端控制器，跳转：forword，重定向：redirect

package com.lyx.web;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
@RequestMapping(\"/jump\")
public class ForwardController {

    @RequestMapping(\"/test1\")
    public String test1(){
        System.out.println(\"test1\");
        return \"forward:/hello.jsp\";
    }
    @RequestMapping(\"/test2\")
    public String test2(){
        System.out.println(\"test2\");
        //return \"forward:/hello/test1\";//绝对路径。跨类跳转到hello的test1方法
        return \"forward:test1\";//相对路径，当前本类的test1
    }
    @RequestMapping(\"/test3\")
    public String test3(){
        System.out.println(\"test3\");
        return \"redirect:/hello.jsp\";//重定向到hello.jsp
    }
    @RequestMapping(\"/test4\")
    public String test4(){
        System.out.println(\"test4\");
        //return \"redirect:/hello/test1\";//绝对路径。跨类跳转到hello的test1方法
        return \"redirect:test3\";//相对路径，重定向到当前本类的test1
    }
}

1.4 细节

1. 在增删改之后，为了防止请求重复提交，要用重定向redirect跳转，如果用forward，每次刷新页面都会重新提交一次数据
2. 在查询之后，我们希望的就是每次跳转都重新刷新数据，所以用forward

2. 传值

2.1 request作用域与session作用域

2.1.1 request作用域

• 后端控制器

@Controller
@RequestMapping(\"/data\")
public class DataController {

    @RequestMapping(\"/test1\")
    public String test1(HttpServletRequest request){
        System.out.println(\"test1\");
        request.setAttribute(\"name\",\"张三\");
        request.setAttribute(\"age\",22);
        return \"data\";
    }
}

• data.jsp页面,JSP取值

<body>
name:${name}<br/>
age:${age}
body>

• Tomcat运行，访问http://locahost:8080/data/test1
  

2.1.2 session作用域

@Controller
@RequestMapping(\"/data\")
public class DataController {

    @RequestMapping(\"/test1\")
    public String test1(HttpServletRequest request, HttpSession session){
        session.setAttribute(\"birth\",new Date());
        System.out.println(\"test1\");
        request.setAttribute(\"name\",\"张三\");
        request.setAttribute(\"age\",22);
        return \"index\";
    }
}

• JSP取值

<body>
    birth:<fmt:formatDate value=\"${sessionScope.birth}\" pattern=\"yyyy-MM-dd\"/><br/>
    name :  ${requestScope.name}<br/>
    age  :   ${requestScope.age}<br/>
body>

• Tomcat运行，访问路径http://localhost:8080/data/test1
  

2.2 Model

2.2.1 model–>request作用域

当我们把数据存在model中的时候呢，model会把这个数据复制到request作用域

• 后端控制器

@Controller
@RequestMapping(\"/data\")
public class DataController {

    @RequestMapping(\"/test2\")
    public String test2(Model model){
        model.addAttribute(\"gender\",true);
        return \"data\";
    }
}

• 当我们把数据存在model中的时候呢，model把这个数据复制到request作用域，所以所有model中的数据都可以通过以下方式调用
• data.jsp页面

<body>
    gender:${requestScope.gender}
body>

• Tomcat运行，访问http://locahost:8080/data/test2
  

2.2.2 @SessionAttributes

通过注解设置key值，model向session作用域中存数据

• 后端控制器

@Controller
@RequestMapping(\"/data\")
@SessionAttributes(names = {\"city\",\"hobby\"})
public class DataController {
    @RequestMapping(\"/sss\")
    public String test(Model model){
        model.addAttribute(\"city\",\"北京\");
        model.addAttribute(\"hobby\",\"football\");
        return \"index\";
    }
}

• JSP取值

<body>
   city:${sessionScope.city}<br/>
    hobby:${sessionScope.hobby}
body>

• Tomcat运行，访问路径：http://localhost:8080/data/sss

2.2.3 清除所有通过model存入session的数据

@Controller
@RequestMapping(\"/data\")
public class DataController {
    
    @RequestMapping(\"ds\")
    public String clean(SessionStatus sessionStatus){
        sessionStatus.setComplete();
        return \"index\";
    }
}

2.2.4 ModelAndView集中管理跳转和传值

ModelAndView是一个用来做数据整合的类
，Model就是数据，View就是视图（.jsp文件）

• 后端控制器

@Controller
@RequestMapping(\"/data\")
@SessionAttributes(names = {\"city\",\"hobby\"})
public class DataController {

    @RequestMapping(\"/aaa\")
    public ModelAndView test(){
    	//新建ModelAndView对象
        ModelAndView modelAndView = new ModelAndView();
        //设置视图名，即跳转的路径
        modelAndView.setViewName(\"forward:/index.jsp\");
        //增加数据
        modelAndView.addObject(\"Singer\",\"刘雨昕\");
        return modelAndView;
    }

• JSP取值，用EL表达式即可

<body>
   Singer:${requestScope.Singer}
body>

• Tomcat运行，访问http:/localhost:8080/data/aaa