SpringMVC__简单文件上传与下载

一、文件上传
1、要用的基本两个包：

2、简单的表单：

<form action="/SpringDemo08/upLoad" method="post" enctype="multipart/form-data">
        账号:<input type="text" name="userName"><br>
        头像:<input type="file" name="file"><br>
        <input type="submit" value="提交">
    </form>

这里重点是：
method="post"
enctype="multipart/form-data"

必须是post方式提交，也必须设置enctype为
multipart/form-data，

controller

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.UnsupportedEncodingException;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.multipart.MultipartFile;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class UploadFile {
    /**
     * 文件上传
     * @param file
     * @return
     * @throws IllegalStateException
     * @throws IOException
     */
    @RequestMapping("/upLoad")
    @ResponseBody
    public String upLoad(MultipartFile file) throws IllegalStateException, IOException {
        // TODO Auto-generated method stub
        // getOriginalFilename()获取原始文件名(在客户端时的文件名)
        //getFileName() 在服务器上的文件名.
        String filename = file.getOriginalFilename();
        File file2 = new File("D:/imgs/"+filename);
        //这里你可以进行重命名也可以把路径入库
     //这里我就不做其他业务操作了

        //MultipartFile中的transferTo不能使用两次
        //因为http post文件流只可以接收读取一次，传输完毕则关闭流。
        //可以把流保存为文件1，然后对文件1进行复制，移动等操作
        //transferTo转存文件到指定路径
        file.transferTo(file2);
        return "上传成功";
    }
}

applicationContext.xml配置：

<!-- 配置文件上传的处理器 -->
    <bean class="org.springframework.web.multipart.commons.CommonsMultipartResolver" id="multipartResolver">
        <property name="maxUploadSize" value="5242880"/>
    </bean>

CommonsMultipartResolver这个Bean的id必须为multipartResolver，
原因：CommonsMultipartResolver Bean是在中央控制器DispatcherServlet中加载的，而DispatcherServlet是通过名字来查找这个Bean的。而其他的，则是按照类型查找。

二、文件下载

1. 方式一:基于ResponseEntity实现

@RequestMapping("/download ")
public ResponseEntity<byte[]> download(HttpServletRequest request) throws IOException {
    // 需要下载的文件
    File file = new File("C:\\Users\\Administrator\\Pictures\\Saved Pictures\\2.jpg");
    byte[] body = null;
    InputStream is = new FileInputStream(file);
    body = new byte[is.available()];
    is.read(body);
    HttpHeaders headers = new HttpHeaders();
    headers.add("Content-Disposition", "attchement;filename=" + file.getName());
    HttpStatus statusCode = HttpStatus.OK;
    ResponseEntity<byte[]> entity = new ResponseEntity<byte[]>(body, headers, statusCode);
    return entity;
}

1. 方式二：通用下载实现

/**
     * 文件下载
     * @param req
     * @param resp
     * @throws IOException
     */
    @RequestMapping("/downLoad")
    @SuppressWarnings("resource")
    public void downLoad(HttpServletRequest req,HttpServletResponse resp) throws IOException {
        // TODO Auto-generated method stub
        File file = new File("C:\\Users\\Administrator\\Pictures\\Saved Pictures\\2.jpg");
        req.setCharacterEncoding("utf-8");
        resp.setContentType("multipart/form-data");
        resp.setHeader("Content-Disposition", "attachment;fileName="+file.getName() );
        FileInputStream inputStream = new FileInputStream(file);
        ServletOutputStream outputStream = resp.getOutputStream();
        int num = 0;
        byte[] b = new byte[1024]; 
        while ((num = inputStream.read(b)) != -1) {
            outputStream.write(b, 0, num);
        }
        outputStream.flush();
        outputStream.close();
        inputStream.close();
    }

SpringMVC__简单文件上传与下载

原文：https://www.cnblogs.com/zhangsonglin/p/10951890.html