技术教程 编程教程 SpringMVC02:返回值、json数据、文件上传、拦截器 正文

SpringMVC02:返回值、json数据、文件上传、拦截器

2023-02-12,,,

 一、响应返回值
1、搭建环境（两个webapp，不要选错）

2、响应之返回值是String类型

package cn.itcast.controller;

import cn.itcast.domain.User;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

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

@Controller

@RequestMapping("/user")

public class UserController {

    @RequestMapping("/testString")

    public String testString(Model model){

        System.out.println("testString方法执行了");

        //模拟从数据库中查询数据库的User对象

        User user = new User();

        user.setUsername("美美");

        user.setPassword("123");

        user.setAge(19);

        //model对象

        model.addAttribute("user",user);

        return "success";

    }

}

3、响应之返回值是void类型

package cn.itcast.controller;

import cn.itcast.domain.User;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

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

import javax.servlet.ServletException;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

@Controller

@RequestMapping("/user")

public class UserController {

    /**

     * 返回值类型是void

     * 请求转发一次请求，不用去编写项目的名称

     * @param request

     * @return

     */

    @RequestMapping("/testVoid")

    public void testVoid(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("testVoid方法执行了");

        //编写请求转发的程序

        //request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);

        //也可以选择重定向，相当于发送了新的请求，需要加项目路径

        //response.sendRedirect(request.getContextPath()+"/index.jsp");

        //也可能会直接进行响应--直接发请求

        //设置中文乱码

        response.setCharacterEncoding("UTF-8");

        response.setContentType("text/html;charset=UTF-8");

        response.getWriter().print("你好");

        return;

    }

}

4、响应之返回值是ModelAndView类型

package cn.itcast.controller;

import cn.itcast.domain.User;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

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

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 {

    //之前类型的底层也都是ModelAndView

    /**

     * testModelAndView

     * @return ModelAndView 对象

     */

    @RequestMapping("/testModelAndView")

    public ModelAndView testModelAndView(){

        //创建ModelAndView对象

        ModelAndView mv = new ModelAndView();

        System.out.println("testModelAndView方法执行了");

        //模拟从数据库中查询数据库的User对象

        User user = new User();

        user.setUsername("美美");

        user.setPassword("123");

        user.setAge(19);

        //把user对象存储到mv对象中，也会把user对象存入到request对象中

        mv.addObject("user",user);

        //跳转到哪个页面

        mv.setViewName("success");//利用视图解析器进行跳转

        return mv;

    }

}

5、响应之使用forward和redirect进行页面跳转（转发和重定向的关键字）
此时无法使用视图解析器ModelAndView

<a href="user/testForwardOrRedirect">testForwardOrRedirect</a>

package cn.itcast.controller;

import cn.itcast.domain.User;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

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

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 {

    /**

     * 使用关键字的方式进行转发或重定向

     * @return

     */

    @RequestMapping("/testForwardOrRedirect")

    public String testForwardOrRedirect(){

        System.out.println("testForwardOrRedirect方法执行了");

        //请求的转发

        return "forward:/WEB-INF/pages/success.jsp";//表明使用请求转发

        //重定向

        //return "redirect:/index.jsp";

    }

}

二、响应json数据
1、响应json数据之过滤静态资源

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

    <%--引入JQuery--%>

    <script src="js/jquery.min.js"></script>

    <script>

        //页面加载，绑定单击事件

        $(function(){

            $("#btn").click(function (){

                alert("hello button");

            });

        });

    </script>

</head>

<body>

    <a href="user/testString">test字符串</a><br>

    <a href="user/testVoid">testVoid</a><br>

    <a href="user/testModelAndView">testVoid</a><br>

    <a href="user/testForwardOrRedirect">testForwardOrRedirect</a><br>

    <button id="btn">发送ajax请求</button>

</body>

</html>
<?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">

    <!--配置前端控制器，告诉哪些静态资源不拦截-->

    <!-- 设置静态资源不过滤 -->

    <mvc:resources location="/css/" mapping="/css/**"/> <!-- 样式 -->

    <mvc:resources location="/images/" mapping="/images/**"/> <!-- 图片 -->

    <mvc:resources location="/js/" mapping="/js/**"/> <!-- javascript -->

    <!--开启SpringMVC框架注解的支持-->

    <mvc:annotation-driven/>

</beans>

2、响应json数据之发送ajax的请求

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

    <%--引入JQuery--%>

    <script src="js/jquery.min.js"></script>

    <script>

        //页面加载，绑定单击事件

        $(function(){

            alert("hehe");

            $("#btn").click(function(){

                alert("hehe");

                $.ajax({

                    //编写json格式，设置属性和值

                    url:"user/testAjax",

                    contentType:"application/json;charset=UTF-8",

                    data:'{"username":"hehe","password":"qaz123","age":30}',//便于嵌套

                    dataType:"json",

                    type:"post",

                    success:function(data){

                        //data是服务器端响应的json数据，进行数据解析

                    }

                });

            });

        });

    </script>

</head>

<body>

    <a href="user/testString">test字符串</a><br>

    <a href="user/testVoid">testVoid</a><br>

    <a href="user/testModelAndView">testVoid</a><br>

    <a href="user/testForwardOrRedirect">testForwardOrRedirect</a><br>

    <button id="btn">发送ajax请求</button>

</body>

</html>
<?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">

    <!--配置前端控制器，告诉哪些静态资源不拦截-->

    <!-- 设置静态资源不过滤 -->

    <mvc:resources location="/css/" mapping="/css/**"/> <!-- 样式 -->

    <mvc:resources location="/images/" mapping="/images/**"/> <!-- 图片 -->

    <mvc:resources location="/js/**" mapping="/js/**"/> <!-- javascript -->

    <!--开启SpringMVC框架注解的支持-->

    <mvc:annotation-driven/>

</beans>

3、响应json数据之响应json格式数据

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

    <%--引入JQuery--%>

    <script src="js/jquery.min.js"></script>

    <script>

        //页面加载，绑定单击事件

        $(function(){

            // 绑定点击事件

            $("#btn").click(function(){

                $.ajax({

                    url:"user/testAjax",

                    contentType:"application/json;charset=UTF-8",

                    data:'{"addressName":"aa","addressNum":100}',

                    dataType:"json", type:"post",

                    success:function(data){

                    alert(data);

                    alert(data.username);

                    alert(data.password);

                    alert(data.age)

                }

                });

            });

        });

    </script>

</head>

<body>

    <a href="user/testString">test字符串</a><br>

    <a href="user/testVoid">testVoid</a><br>

    <a href="user/testModelAndView">testVoid</a><br>

    <a href="user/testForwardOrRedirect">testForwardOrRedirect</a><br>

    <button id="btn">发送ajax请求</button>

</body>

</html>


package cn.itcast.controller;

import cn.itcast.domain.User;

import org.springframework.stereotype.Controller;

import org.springframework.ui.Model;

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 {

    /**

     * 模拟异步请求响应

     * @param user

     */

    @RequestMapping("/testAjax")

    public @ResponseBody User testAjax(@RequestBody User user){

        System.out.println("testAjax方法执行了");

        //客户端发送ajax请求，传递了json字符串，后端已经把json字符串封装到user对象中

        System.out.println(user);

        //做数据的响应，可以模拟查询数据库

        user.setUsername("ahahhah");

        user.setAge(45);

        //数据响应

        return user;

    }

}

三、文件上传
1、上传原理分析和搭建环境

get会写到地址栏上

2、传统方式上传代码回顾

    @RequestMapping("/fileupload1")

    public String fileupload1(HttpServletRequest request, HttpServletResponse response) throws Exception {

        System.out.println("文件上传……");

        //使用servlet组件完成文件上传

        //指定文件上传的位置

        String path = request.getSession().getServletContext().getRealPath("/uploads/");

        //判断该 路径是否存在

        File file = new File(path);

        if (!file.exists()){

            //创建该文件夹

            file.mkdirs();

        }

        //解析request对象，获取到上传的文件项

        DiskFileItemFactory factory = new DiskFileItemFactory();

        ServletFileUpload upload = new ServletFileUpload(factory);

        //解析request

        List<FileItem> items = upload.parseRequest(request);

        //遍历

        for (FileItem item : items) {

            //判断当前item是否是上传文件项

            if (item.isFormField()){

                //说明是普通的表单项

            }else{

                //说明是上传文件项

                //获取到上传文件的名称

                String filename = item.getName();

                //把文件名称设置为唯一值

                String uuid = UUID.randomUUID().toString().replace("-", "");

                filename = uuid+filename;

                //完成文件上传

                item.write(new File(path,filename));

                //删除临时文件

                item.delete();

            }

        }

        return "success";

    }

3、Springmvc方式上传原理分析

文件解析器对象：CommonsMultipartResolver
4、Springmvc方式上传代码

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

    <br>

    <h3>SpringMVC方式文件上传</h3>

    <form action="user/fileupload2" method="post" enctype="multipart/form-data">

        选择文件：<input type="file" name="upload" /> <br>

        <input type="submit" value="上传" />

    </form>

</body>

</html>

    /**

     * Spring MVC方式上传

     * @param request

     * @param upload

     * @return

     * @throws Exception

     */

    @RequestMapping("/fileupload2")

    public String fileupload2(HttpServletRequest request, MultipartFile upload) throws Exception {

        System.out.println("Spring文件上传……");

        //使用servlet组件完成文件上传

        //指定文件上传的位置

        String path = request.getSession().getServletContext().getRealPath("/uploads/");

        //判断该 路径是否存在

        File file = new File(path);

        if (!file.exists()){

            //创建该文件夹

            file.mkdirs();

        }

        //说明是上传文件项

        //获取到上传文件的名称

        String filename = upload.getOriginalFilename();

        //把文件名称设置为唯一值

        String uuid = UUID.randomUUID().toString().replace("-", "");

        filename = uuid+filename;

        //完成文件上传

        upload.transferTo(new File(path,filename));

        return "success";

    }

4、跨服务器上传分析和搭建环境

创建了两个tomcat：SpringMVC和fileupload

5、跨服务器上传代码

<dependency>

      <groupId>com.sun.jersey</groupId>

      <artifactId>jersey-core</artifactId>

      <version>1.18.1</version>

    </dependency> <dependency>

    <groupId>com.sun.jersey</groupId>

    <artifactId>jersey-client</artifactId>

    <version>1.18.1</version>

  </dependency>
    /**

     * 跨服务器文件上传

     * @param upload

     * @return

     * @throws Exception

     */

    @RequestMapping("/fileupload3")

    public String fileupload3(MultipartFile upload) throws Exception {

        System.out.println("跨服务器文件上传……");

        //定义上传文件服务器的路径

        String path = "http://localhost:9090/uploads/";//写加号就不需要拼了

        //说明是上传文件项

        //获取到上传文件的名称

        String filename = upload.getOriginalFilename();

        //把文件名称设置为唯一值

        String uuid = UUID.randomUUID().toString().replace("-", "");

        filename = uuid+filename;

        //完成文件上传，跨服务器上传

        //创建客户端对象

        Client client = Client.create();

        //和图片服务器进行连接

        WebResource webResource = client.resource(path+filename);

        //上传文件

        webResource.put(upload.getBytes());

        return "success";

    }

四、异常处理--友好页面
1、分析和搭建环境

2、异常处理之演示程序异常

package cn.itcast.controller;

import org.springframework.stereotype.Controller;

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

@Controller

@RequestMapping("/user")

public class UserController {

    @RequestMapping("/testException")

    public String testException() throws Exception{

        System.out.println("testException执行了……");

        //模拟异常

        int i = 1 / 0;

        return "success";

    }

}

3、异常处理代码编写
步骤：

编写自定义异常类（提示信息）

package cn.itcast.exception;

/**

 * 自定义异常类

 */

public class SysException extends Exception{

    public SysException(String message) {

        this.message = message;

    }

    //存储异常信息

    private String message;

    @Override

    public String getMessage() {

        return message;

    }

    public void setMessage(String message) {

        this.message = message;

    }

}

编写异常处理器

package cn.itcast.exception;

import org.springframework.web.servlet.HandlerExceptionResolver;

import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * 异常处理器对象

 */

public class SysExceptionResolver implements HandlerExceptionResolver {

    /**

     * 处理异常的业务逻辑

     * @param httpServletRequest

     * @param httpServletResponse

     * @param o 处理器对象

     * @param ex 异常对象

     * @return

     */

    @Override

    public ModelAndView resolveException(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception ex) {

        //获取到异常对象

        SysException e = null;

        //判断ex是SysException类型的

        if(ex instanceof SysException){

            e = (SysException) ex;

        }else{

            e = new SysException("系统正在维护");

        }

        //创建ModelAndView对象

        ModelAndView mv = new ModelAndView();

        mv.addObject("errorMsg",e.getMessage());

        mv.setViewName("error");

        return mv;

    }

}

配置异常处理器（跳转到友好提示页面）

<!--配置异常处理器对象-->

<bean id="sysExceptionResolver" class="cn.itcast.exception.SysExceptionResolver" />

<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>

<html>

<head>

    <title>Title</title>

</head>

<body>

${errorMsg}

</body>

</html>

五、SpringMVC拦截器
1、介绍和搭建环境

拦截器链：多个拦截器

拦截器与过滤器的区别：

过滤器什么都能拦，拦截器只能拦controller

2、编写controller

package cn.itcast.controller;

import org.springframework.stereotype.Controller;

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

@Controller

@RequestMapping("/user")

public class UserController {

    @RequestMapping("/testInterceptor")

    public String testInterceptor() throws Exception{

        System.out.println("testInterceptor执行了……");

        try {

            //模拟异常

            int i = 1 / 0;

        } catch (Exception e) {

            e.printStackTrace();//在控制台打印异常信息，保留

            //向上抛出自定义异常信息

        }

        return "success";

    }

}

3、拦截器入门代码

<?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">

    <!--配置拦截器-->

    <mvc:interceptors>

        <!--配置拦截器-->

        <mvc:interceptor>

            <!--要拦截的具体方法-->

            <mvc:mapping path="/user/*"/>

            <!--不要拦截的方法-->

            <!--<mvc:exclude-mapping path=""/>-->

            <!--配置拦截器对象-->

            <bean class="cn.itcast.interceptor.MyInterceptor1"></bean>

        </mvc:interceptor>

    </mvc:interceptors>

    <!--开启SpringMVC框架注解的支持-->

    <mvc:annotation-driven/>

</beans>
package cn.itcast.interceptor;

import org.springframework.web.servlet.HandlerInterceptor;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * 自定义拦截器

 */

public class MyInterceptor1 implements HandlerInterceptor {

    //jdk1.8之后，接口中可以对方法进行实现

    /**

     * 预处理controller方法执行前

     * @param request

     * @param response

     * @param handler

     * @return true放行，执行下一个拦截器；如果没有，执行controller中的方法

     *         false不放行

     * @throws Exception

     */

    @Override

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {

        System.out.println("MyInterceptor1执行了");

        return true;

    }

}

4、拦截器接口方法演示

来自为知笔记(Wiz)

SpringMVC02:返回值、json数据、文件上传、拦截器的相关教程结束。

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