文件上传下载及上传预览

js文件 实现当上传图片的时候可以预览图片

$(function () {
               $("input[type=file]").change(function(){
                   // 获取FileList的第一个元素
                   var t = $(this)[0].files[0];
                  /* t.name;//获取图片名字
                   t.size//图片大小
                   t.type;//类型*/
                   var src = window.URL.createObjectURL(t);
                   $(this).next().attr("src",src);
               });
           });

HTML文件

<input type="file" name="imgFile" accept="image/*"/>
            <img    width="160px" height="120px"/></br>
<input type="file" name="imgFile" accept="image/*"/>
            <img    width="160px" height="120px"/></br>
 <input type="file" name="imgFile" accept="image/*"/>
            <img    width="160px" height="120px"/></br>

文件上传 先导入jar包

<dependency>
      <groupId>commons-fileupload</groupId>
      <artifactId>commons-fileupload</artifactId>
      <version>1.3.1</version>
</dependency>

//单文件上传
    @RequestMapping("/upload")
    public String up(@RequestParam("imgFile")MultipartFile imgFile)
        throws IOException ,IllegalStateException {
        String filePath = "F://upload/";
        String fileName = imgFile.getOriginalFilename();

        imgFile.transferTo(new File(filePath+fileName));
        return "/index.jsp";
    }

    //多文件上传
    @RequestMapping("/uploads")
    public String ups(HttpServletRequest request)
            throws IOException ,IllegalStateException{
        //获取上传的文件集合
        List<MultipartFile> files = ((MultipartHttpServletRequest)request).getFiles("imgFile");
        //设定绝对路径
        String filePath = "F://upload/";
        System.out.println(files.size());
        //遍历上传文件
        for(MultipartFile file:files){
            //判断文件是否为空
            if(!file.isEmpty()){
                //调用transferTo(new File())方法上传文件
                file.transferTo(new File(filePath+file.getOriginalFilename()));
            }
        }
        return "/index.jsp";
    }

文件下载

@RequestMapping("/download")
    protected void download(HttpServletResponse response)
            throws Exception {
        //选择下载文件
        String filePath = "F://upload/2.jpg";
        File file = new File(filePath);
        String fileName = filePath.substring(filePath.lastIndexOf(File.separator)+1);
        //文件路径有中文，会无法识别文件格式，
        //URLEncoder.encode();转换字符串格式
        fileName = URLEncoder.encode(fileName, "UTF-8");
        response.reset();
        //文件响应MIME类型，
        //不知道类型application/octet-stream
        response.setContentType("application/octet-stream");
        //激活文件下载对话框
        response.addHeader("Content-Disposition", "attachment;filename="+fileName);
        /*String len = String.valueOf(file.length());
        //指定文件长度
        response.setHeader("Content-Length", len);*/
        //IO流读写文件，将文件下载
        OutputStream os = response.getOutputStream();
        FileInputStream is = new FileInputStream(file);
        byte[] b = new byte[1024];
        int n;
        while((n=is.read(b))!=-1){
            os.write(b, 0, n);
        }
        is.close();
        os.close();
        System.out.println("下载完成");

    }