浅谈在Spring MVC中如何实现文件上传、下载

Spring MVC文件上传下载

单文件上传

介绍：底层是使用 Apache fileupload 组件完成上传，Spring MVC 对这种方式进行了封装。
步骤如下：
1、先在pom.xml中导入相关依赖：

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.5</version>
</dependency>

<dependency>
    <groupId>commons-fileupload</groupId>
    <artifactId>commons-fileupload</artifactId>
    <version>1.3.3</version>
</dependency>

2、JSP

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page isELIgnored="false" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <form action="/file/upload" method="post" enctype="multipart/form-data">
        <input type="file" name="img"/>
        <input type="submit" value="上传"/>
    </form>
    <img src="${path}">
</body>
</html>

几点说明：

文件上传，input的type属性需要设置成"file"

form标签中的method需设置成"post"，因为get请求只能将文件名上传给服务器

form标签中的enctype设置为 multipart-form-data,否则只能将文件名上传给服务器

3、Handler

package com.zyc.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.multipart.MultipartFile;

import javax.servlet.http.HttpServletRequest;
import java.io.File;
import java.io.IOException;

@Controller
@RequestMapping("/file")
public class FileHandler {
    
    

    @PostMapping("/upload")
    public String upload(MultipartFile img, HttpServletRequest request){
    
    
        if(img.getSize()>0){
    
    
            //获取保存上传文件的file路径
            String path = request.getServletContext().getRealPath("file");
            //获取上传的文件名
            String name = img.getOriginalFilename();
            File file = new File(path,name);
            try {
    
    
                img.transferTo(file);
                //保存上传之后的文件路径
                request.setAttribute("path","/file/"+name);
            } catch (IOException e) {
    
    
                e.printStackTrace();
            }
        }
        return "upload";
    }
}

4、在spring-mvc.xml中配置上传组件

<!-- 配置上传组件 -->
<bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver"></bean>

5、web.xml 添加如下配置，否则客户端无法访问 png

<servlet-mapping>
    <servlet-name>default</servlet-name>
    <url-pattern>*.png</url-pattern>
</servlet-mapping>

多文件上传

JSP

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ page isELIgnored="false" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <form action="/file/uploads" method="post" enctype="multipart/form-data">
        file1:<input type="file" name="imgs"/><br/>
        file2:<input type="file" name="imgs"/><br/>
        file3:<input type="file" name="imgs"><br/>
        <input type="submit" value="上传"/>
    </form>
    <c:forEach items="${files}" var="file" >
        <img src="${file}" width="300px">
    </c:forEach>
</body>
</html>

Handler

@PostMapping("/uploads")
public String uploads(MultipartFile[] imgs,HttpServletRequest request){
    
    
    List<String> files = new ArrayList<>();
    for (MultipartFile img:imgs){
    
    
        if(img.getSize()>0){
    
    
            //获取保存上传文件的file路径
            String path = request.getServletContext().getRealPath("file");
            //获取上传的文件名
            String name = img.getOriginalFilename();
            File file = new File(path,name);
            try {
    
    
                img.transferTo(file);
                //保存上传之后的文件路径
                files.add("/file/"+name);
            } catch (IOException e) {
    
    
                e.printStackTrace();
            }
        }
    }
    request.setAttribute("files",files);
    return "uploads";
}

@PostMapping:映射了一个POST请求
为Spring MVC的新特性，提供了对Restful风格的支持

文件下载

JSP

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <a href="/file/download/1">1.png</a>
    <a href="/file/download/2">2.png</a>
    <a href="/file/download/3">3.png</a>
</body>
</html>

Handler

@GetMapping("/download/{name}")
public void download(@PathVariable("name") String name, HttpServletRequest request, HttpServletResponse response){
    
    
    if(name != null){
    
    
        name += ".png";
        String path = request.getServletContext().getRealPath("file");
        File file = new File(path,name);
        OutputStream outputStream = null;
        if(file.exists()){
    
    
            response.setContentType("application/forc-download");
            response.setHeader("Content-Disposition","attachment;filename="+name);
            try {
    
    
                outputStream = response.getOutputStream();
                outputStream.write(FileUtils.readFileToByteArray(file));
                outputStream.flush();
            } catch (IOException e) {
    
    
                e.printStackTrace();
            } finally {
    
    
                if(outputStream != null){
    
    
                    try {
    
    
                        outputStream.close();
                    } catch (IOException e) {
    
    
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

@GetMapping，处理get请求

浅谈在Spring MVC中如何实现文件上传、下载

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