【java】根据文件URL在后台设置response的文件流，在前端直接显示或者下载

系统管理员 2024-03-24 05:58 41阅读 0赞

#### 通过url转文件流下载文件 ####

@ApiOperation(value = "根据文件URL下载")
    @GetMapping("/download")
    @ResponseBody
    public void checkDownload(@ApiParam("文件地址") @RequestParam("url") String url,
                              HttpServletResponse response) {
        
        HttpURLConnection conn = null;
        InputStream fis = null;
        try {
        
            File file = new File(url);
            // 取得文件的后缀名。
            String ext = file.getName().substring(file.getName().lastIndexOf(".") + 1).toLowerCase();
            StringBuffer buffername = new StringBuffer(url.substring(url.lastIndexOf("/")+1));
            // 取的文件名
            String filename = buffername.toString();
    
            URL path = new URL(url);
            conn = (HttpURLConnection) path.openConnection();
            conn.setRequestMethod("GET");
            conn.setConnectTimeout(5 * 1000);
            // 通过输入流获取数据
            fis = conn.getInputStream();
    
            byte[] buffer = readInputStream(fis);
            if (null != buffer && buffer.length > 0) {
        
                // 清空response
                response.reset();
                // 设置response的Header
                response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes(StandardCharsets.UTF_8), StandardCharsets.ISO_8859_1));
                response.addHeader("Content-Length", "" + buffer.length);
                OutputStream toClient = response.getOutputStream();
                //response.setContentType("application/x-msdownload");
                response.setContentType("application/octet-stream");
                toClient.write(buffer);
                toClient.flush();
                toClient.close();
            }
        } catch (IOException ex) {
        
            log.error("下载文件异常:", ex);
            throw new RRException("下载异常，请稍后再试。");
        } finally {
        
            if (conn != null) {
        
                conn.disconnect();
            }
            if (fis != null) {
        
                try {
        
                    fis.close();
                } catch (IOException ioe) {
        
                    log.error("下载文件->关闭流异常:", ioe);
                }
            }
        }
    
    }
    
    /**
         * 从输入流中获取数据
         *
         * @param fis : InputStream
         * @return byte[]
         * @author chenp
         * @date 2023/3/28 11:31
         */
    private byte[] readInputStream(InputStream fis) throws IOException {
        
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len = fis.read(buffer)) != -1) {
        
            outStream.write(buffer, 0, len);
        }
        fis.close();
        return outStream.toByteArray();
    }