猿创征文｜Java下载文件到本地目录(弹框选择)

Posted 2022-09-02 小花皮猪

需求

提供一个接口,前端通过按钮下载文件,根据不同的id下载对应的文件

编写接口相关代码

controller

    /**
     * 下载文件
     *
     * @param signId
     */
    @GetMapping("/downloadFile")
    @ApiOperationSupport(order = 5)
    @ApiOperation(value = "下载文档", notes = "传入signId")
    public void downloadFile(@ApiParam(value = "签署id", required = true) @RequestParam Long signId, HttpServletResponse response) throws Exception 
        signDocumentService.downloadFile(signId,response);
    

mapper

	/**
	 * 根据singId查询Attach
	 *
	 * @param singId
	 * @return SignDocument
	 */
	List<Map<String, String>> selectAttachs(@Param("singId") Long singId);

mapper.xml

   <select id="selectAttachs" resultType="map" >
        select
            ba.link filePath,ba.original_name fileName
        from dmyz_sign_document dsd
        left join blade_attach ba on ba.id=dsd.attach_id
        where sign_id =#singId and  dsd.is_deleted = 0
    </select>

service

	/**
	 * 根据id查询附件并下载
	 *
	 * @param signId
	 * @param response
	 * @throws Exception
	 */
    void downloadFile(Long signId, HttpServletResponse response) throws IOException;

serviceImpl

这里我要从oss上下载,所以我先从oss下载到项目本地了,不然File无法识别远程文件,只能识别本地文件,这块逻辑自行修改,代码参考即可

  /**
     * 根据id查询附件并下载
     *
     * @param signId
     * @param response
     * @throws Exception
     */
    @Override
    public void downloadFile(Long signId, HttpServletResponse response) throws IOException 
        String path = null;
        String download = null;
        ServletOutputStream out=null;
        FileInputStream fis=null;
        try 
            // 根据signId查询签署文档
            List<Map<String, String>> maps = signDocumentMapper.selectAttachs(signId);
            // 如果不为空
            if (!maps.isEmpty()) 
                for (Map<String, String> map : maps) 
                    String link =  map.get("filePath");
                    String uuid = UUID.randomUUID().toString().replace("-", "");
                    // 文件名称 uuid随机生成
                    String fileName =uuid+PDF;
                    // 把oss文件下载到项目本地
                    path = SignDocumentServiceImpl.class.getClass().getResource("/").getPath() +
                            FileUtil.getNameWithoutExtension(link) + PDF;
                    // 把获取到的oss文件链接下载到本地
                    download = download(link, path);
                    File file = new File(download);
                    response.setCharacterEncoding("utf-8");
                    response.setContentType("application/file");
                    response.setHeader("Content-Disposition", "attachment;FileName=" + fileName);
                    out = response.getOutputStream();
                    int len = 0;
                    byte[] buffer = new byte[1024];
                    fis = new FileInputStream(file);
                    while ((len = fis.read(buffer)) > 0) 
                        out.write(buffer, 0, len);
                        out.flush();
                    
                    response.flushBuffer();
                
            
        
        catch (Exception e) 
            log.error("下载单个pdf文件失败,原因:", e);
        
        finally 
            out.close();
            fis.close();
        
    

访问接口测试

浏览器输入

localhost:8080/downloadFile?signId=1001

本地选择保存目录

点击保存 就看到在指定的位置上有我们的文件了

可以正常打开查看