SpringMVC学习(三)

一、响应数据和结果视图

1. 返回值分类

1.1搭建开发环境

坐标

XML 复制代码

 
<!-- 版本锁定 -->
  <properties>
    <spring.version>5.0.2.RELEASE</spring.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-context</artifactId>
      <version>${spring.version}</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-web</artifactId>
      <version>${spring.version}</version>
    </dependency>

    <dependency>
      <groupId>org.springframework</groupId>
      <artifactId>spring-webmvc</artifactId>
      <version>${spring.version}</version>
    </dependency>

    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>servlet-api</artifactId>
      <version>2.5</version>
      <scope>provided</scope>
    </dependency>

    <dependency>
      <groupId>javax.servlet.jsp</groupId>
      <artifactId>jsp-api</artifactId>
      <version>2.0</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>

前端控制器和过滤器

XML 复制代码

<!-- 配置过滤器，解决中文乱码的问题 -->
  <filter>
    <filter-name>characterEncodingFilter</filter-name>
    <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>
    <!-- 指定字符集 -->
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
    <!-- 强制使用指定字符集 -->
    <init-param>
      <param-name>forceEncoding</param-name>
      <param-value>true</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>characterEncodingFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>

  <!--配置前端控制器-->
  <servlet>
    <servlet-name>dispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <!--加载springmvc.xml配置文件，配置的是Spring配置-->
    <init-param>
      <param-name>contextConfigLocation</param-name>
      <param-value>classpath:springmvc.xml</param-value>
    </init-param>
    <!--配置启动加载-->
    <load-on-startup>1</load-on-startup>
  </servlet>
  <servlet-mapping>
      <servlet-name>dispatcherServlet</servlet-name>
      <url-pattern>*.do</url-pattern>
  </servlet-mapping>

springmvc.xml配置文件

XML 复制代码

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xmlns:context="http://www.springframework.org/schema/context"
       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/mvc
           http://www.springframework.org/schema/mvc/spring-mvc.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- 开启注解驱动 -->
    <mvc:annotation-driven />

    <!-- 扫描控制器所在的包 -->
    <context:component-scan base-package="com.qcby.demo" />

    <!-- 视图解析器 -->
    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/pages/" />
        <property name="suffix" value=".jsp" />
    </bean>

</beans>

返回String

Controller方法返回字符串可以指定逻辑视图的名称，根据视图解析器为物理视图的地址。

java 复制代码

package com.qcby.demo;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    /**
     * 返回String
     * @return
     */
    @RequestMapping("/save1.do")
    public String save1(){
        System.out.println("执行了...");
        return "suc";
    }

}

返回值是void

如果控制器的方法返回值编写成void，执行程序报404的异常，默认查找JSP页面没有找到。

可以使用请求转发或者重定向跳转到指定的页面

java 复制代码

package com.qcby.demo;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    /**
     * 返回void
     * 默认查询 /pages/sav2.do.jsp的页面
     * @return
     */
    @RequestMapping("/save2.do")
    public void save2(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("执行了...");
        // request.getRequestDispatcher("/pages/suc.jsp").forward(request,response);

        // 做出相应的操作
        response.getWriter().print("hello");
        return;
    }

}

返回值是ModelAndView对象

ModelAndView对象是Spring提供的一个对象，可以用来调整具体的JSP视图

java 复制代码

package com.qcby.demo;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    /**
     * 返回ModelAndView对象的方式
     * @return
     */
    @RequestMapping("/save3.do")
    public ModelAndView save3(){
        System.out.println("执行了...");
        // 创建mv对象
        ModelAndView mv = new ModelAndView();
        // 把一些数据，存储到mv对象中
        mv.addObject("msg","用户名或者密码已经存在");
        // 设置逻辑视图的名称
        mv.setViewName("suc");
        return mv;
    }

}

2.SpringMVC框架提供的转发和重定向

forward请求转发

controller方法返回String类型，想进行请求转发也可以编写成

java 复制代码

package com.qcby.demo;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    /**
     * 返回String
     * 请求转发
     * @return
     */
    @RequestMapping("/save4.do")
    public String save4(){
        System.out.println("执行了...");
        return "forward:/pages/suc.jsp";
    }


}

redirect重定向

java 复制代码

package com.qcby.demo;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@Controller
@RequestMapping("/user")
public class UserController {

    /**
     * 返回String
     * 重定向
     * @return
     */
    @RequestMapping("/save5.do")
    public String save5(){
        System.out.println("执行了...");
        return "redirect:/pages/suc.jsp";
    }

}