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SpringMVC-文件上传和下载

文件上传和下载

文件上传和下载
- 1. 文件上传
- 2. 文件下载
  - 1. 前端设计
  - 2. controller设置

1. 文件上传

1. 前端设计

前端表单要求：为了能上传文件，必须将表单的method设置为POST，并将enctype设置为multipart/form-data。只有在这样的情况下，浏览器才

会把用户选择的文件以二进制数据发送给服务器；

<%--
  Created by IntelliJ IDEA.
  User: Wang
  Date: 2020/9/11
  Time: 16:48
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>

  <form action="${pageContext.request.contextPath}/upload" enctype="multipart/form-data" method="post">
    <input type="file" name="file">
    <input type="submit" value="upload">
  </form>

  </body>
</html>

2. 导入依赖

commons-fileupload

<dependencies>
    <!--文件上传-->
    <dependency>
        <groupId>commons-fileupload</groupId>
        <artifactId>commons-fileupload</artifactId>
        <version>1.4</version>
    </dependency>
    <!--servlet-api导入高版本的-->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>4.0.1</version>
    </dependency>
</dependencies>

3. 配置Spring

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

    <context:component-scan base-package="com.wang.controller"/>

    <mvc:annotation-driven/>
    <mvc:default-servlet-handler/>

    <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver"
          id="internalResourceViewResolver">
        <property name="prefix" value="/WEB-INF/jsp/"/>
        <property name="suffix" value=".jsp"/>
    </bean>

    <mvc:annotation-driven>
        <mvc:message-converters register-defaults="true">
            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8"/>
            </bean>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper">
                    <bean class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean">
                        <property name="failOnEmptyBeans" value="false"/>
                    </bean>
                </property>
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

    <!--文件上传配置-->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- 请求的编码格式, 必须和jsp的pageEncoding属性一致, 以便正确读取表单的内容, 默认为ISO-8859-1 -->
        <property name="defaultEncoding" value="utf-8"/>
        <!-- 上传文件大小上限, 单位为字节 (10485760 = 10M) -->
        <property name="maxUploadSize" value="10485760"/>
        <property name="maxInMemorySize" value="40960"/>
    </bean>


</beans>

注意

这个bena的id必须为：multipartResolver ，否则上传文件会报400的错误！

4. 编写controller

有两种上传的方式

1. getOriginalFilename方法

package com.wang.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;

@RestController
public class FileController {

    //@RequestParam("file") 将name=file控件得到的文件封装成CommonsMultipartFile 对象
    //批量上传CommonsMultipartFile则为数组即可
    @RequestMapping("/upload")
    public String fileUpload(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {

        //获取文件名 : file.getOriginalFilename();
        String uploadFileName = file.getOriginalFilename();

        //如果文件名为空，直接回到首页！
        if ("".equals(uploadFileName)) {
            return "redirect:/index.jsp";
        }
        System.out.println("上传文件名 : " + uploadFileName);

        //上传路径保存设置
        String path = request.getServletContext().getRealPath("/upload");
        //如果路径不存在，创建一个
        File realPath = new File(path);
        if (!realPath.exists()) {
            realPath.mkdir();
        }
        System.out.println("上传文件保存地址：" + realPath);

        InputStream is = file.getInputStream(); //文件输入流
        OutputStream os = new FileOutputStream(new File(realPath, uploadFileName)); //文件输出流

        //读取写出
        int len = 0;
        byte[] buffer = new byte[1024];
        while ((len = is.read(buffer)) != -1) {
            os.write(buffer, 0, len);
            os.flush();
        }
        os.close();
        is.close();
        return "redirect:/index.jsp";
    }
}

2. Tansto方法

package com.wang.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;

@RestController
public class FileController {
    /*
     * 采用file.Transto 来保存上传的文件
     */
    @RequestMapping("/upload2")
    public String fileUpload2(@RequestParam("file") CommonsMultipartFile file, HttpServletRequest request) throws IOException {

        //上传路径保存设置
        String path = request.getServletContext().getRealPath("/upload");
        File realPath = new File(path);
        if (!realPath.exists()) {
            realPath.mkdir();
        }
        //上传文件地址
        System.out.println("上传文件保存地址：" + realPath);

        //通过CommonsMultipartFile的方法直接写文件（注意这个时候）
        file.transferTo(new File(realPath + "/" + file.getOriginalFilename()));

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

2. 文件下载

1. 前端设计

利用a标签实现跳转

<%--
  Created by IntelliJ IDEA.
  User: Wang
  Date: 2020/9/11
  Time: 16:48
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>

  <a href="${pageContext.request.contextPath}/download">点击下载</a>


  </body>
</html>

2. controller设置

文件下载步骤：

1、设置 response 响应头

2、读取文件 -- InputStream

3、写出文件 -- OutputStream

4、执行操作

5、关闭流（先开后关）

package com.wang.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.multipart.commons.CommonsMultipartFile;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;
import java.net.URLEncoder;

@RestController
public class FileController {

    @RequestMapping(value="/download")
    public String downloads(HttpServletResponse response , HttpServletRequest request) throws Exception {
        //要下载的图片地址
        String path = request.getServletContext().getRealPath("/upload");
        String fileName = "基础语法.jpg";

        //1、设置response 响应头
        response.reset(); //设置页面不缓存,清空buffer
        response.setCharacterEncoding("UTF-8"); //字符编码
        response.setContentType("multipart/form-data"); //二进制传输数据
        //设置响应头
        response.setHeader("Content-Disposition",
                "attachment;fileName=" + URLEncoder.encode(fileName, "UTF-8"));

        File file = new File(path, fileName);
        //2、 读取文件--输入流
        InputStream input = new FileInputStream(file);
        //3、 写出文件--输出流
        OutputStream out = response.getOutputStream();

        byte[] buff = new byte[1024];
        int index = 0;
        //4、执行 写出操作
        while ((index = input.read(buff)) != -1) {
            out.write(buff, 0, index);
            out.flush();
        }
        out.close();
        input.close();
        return null;
    }

}

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原文地址：https://www.cnblogs.com/wang-sky/p/13653087.html