文件上传 - 码农教程

文件上传
　　1） Spring MVC 为文件上传提供了直接的支持，这种支持是通过即插即用的 MultipartResolver 实现的。
　　2） Spring 用 Jakarta Commons FileUpload 技术实现了一个 MultipartResolver 实现类：CommonsMultipartResolver
　　3） Spring MVC 上下文中默认没有装配 MultipartResovler，因此默认情况下不能处理文件的上传工作，如果想使用 Spring 的文件上传功能，需现在上下文中配置 MultipartResolver。

设置步骤：

　　1）导入jar包

　　　　commons-fileupload-1.2.1.jar

　　　 commons-io-2.0.jar

　　2）配置文件上传解析器，

    <!-- 
        处理文件，将客户端上传的File文件，处理为MultipartFile
        注意：文件解析器的bean中id必须设置为multipartResolver
     -->
    <bean id="multipartResolver" class="org.springframework.web.multipart.commons.CommonsMultipartResolver">
        <!-- 设置文件解析的编码，注意：一定要和页面的pageEncoding保持一致 -->
        <property name="defaultEncoding" value="UTF-8"></property>
        <!-- 设置最大上传文件大小 -->
        <property name="maxUploadSize" value="88888888"></property>
    </bean>

　　3）上传页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>

    <a href="down">下载图片</a>
    
    <form action="up1" method="post" enctype="multipart/form-data">
        头像：<input type="file" name="uploadFile" />
        描述：<input type="text" name="desc" />
        <input type="submit" value="上传1" />
    </form>
    
    <form action="up2" method="post" enctype="multipart/form-data">
        头像：<input type="file" name="uploadFile" />
        描述：<input type="text" name="desc" />
        <input type="submit" value="上传2" />
    </form>
    

</body>
</html>

　　4）控制器方法

package com.spring.controller;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.UUID;

import javax.servlet.http.HttpSession;

import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.multipart.MultipartFile;


@Controller
public class Download {
    @RequestMapping("/down")
    public ResponseEntity<byte[]> down(HttpSession session) throws IOException{
        
        //获取下载文件的路径
        String realPath = session.getServletContext().getRealPath("img");
        String finalPath = realPath + File.separator + "2.jpg";
        InputStream is = new FileInputStream(finalPath);
        //available():获取输入流所读取的文件的最大字节数
        byte[] b = new byte[is.available()];
        is.read(b);
        //设置请求头
        HttpHeaders headers = new  HttpHeaders();
        headers.add("Content-Disposition", "attachment;filename=zzz.jpg");
        //设置响应状态
        HttpStatus statusCode = HttpStatus.OK;
        ResponseEntity<byte[]> entity = new ResponseEntity<byte[]>(b, headers, statusCode);
        return entity;
    }
    
    @RequestMapping(value="/up1", method=RequestMethod.POST)
    public String up_old(String desc, MultipartFile uploadFile, HttpSession session) throws IOException {
        //获取上传文件的名称
        String fileName = uploadFile.getOriginalFilename();
        String path = session.getServletContext().getRealPath("photo") + File.separator + fileName;
        //获取输入流
        InputStream is = uploadFile.getInputStream();
        //获取输出流
        File file = new File(path);
        OutputStream os = new FileOutputStream(file);
        /*int i = 0;
        while((i = is.read()) != -1) {
            os.write(i);
        }*/
        
        int i = 0;
        byte[] b = new byte[1024];
        while((i = is.read(b)) != -1) {
            os.write(b, 0, i);
        }
        
        os.close();
        is.close();
        return "success";
    }
    
    
    @RequestMapping(value="/up2", method=RequestMethod.POST)
    public String up(String desc, MultipartFile uploadFile, HttpSession session) throws IOException {
        //获取上传文件的名称
        String fileName = uploadFile.getOriginalFilename();
        String finalFileName = UUID.randomUUID() + fileName.substring(fileName.lastIndexOf("."));
        String path = session.getServletContext().getRealPath("photo") + File.separator + finalFileName;
        File file = new File(path);
        uploadFile.transferTo(file);
        return "success";
    }
    
}

原文地址：https://www.cnblogs.com/lemonzhang/p/12937794.html