Java通过URL下载网络文件，获取文件流并修改文件名

下载网络文件，地址是 http://sk.sit.fosuntech.cn/group1/M00/00/72/CqYKHVn69wyAMl6YAAVf953sp4Y075.pdf
前端调用下载链接

function downloadAttachement(imageId,fileName){    var url = _HTTP_IP_PORT +'repayment/downloadAttachment.do?imageId='+ imageId +'&fileName='+fileName;    var form = $("<form></form>").attr("action", url).attr("method", "post");    form.appendTo('body').submit().remove();}

后台用的spring，接受请求参数

    @RequestMapping(value = "/repayment/downloadAttachment", method = RequestMethod.POST)    @ResponseBody    public String downloadAttachment(String imageId,String fileName,HttpServletRequest request,HttpServletResponse response) {        if (StringUtils.isEmpty(imageId)) {        throw new CommonException("影像ID不能为空！");        }        if (StringUtils.isEmpty(fileName)) {        throw new CommonException("文件名不能为空！");        }        //这里获取的下载链接 http://sk.sit.fosuntech.cn/group1/M00/00/72/CqYKHVn69wyAMl6YAAVf953sp4Y075.pdfString downLoadPath = templateService.getDownloanUrl(imageId);        BufferedInputStream bis = null;          BufferedOutputStream bos = null;          try {//如果不存在乱码的情况可以忽略，由于请求参数文件名为中文，到后台会乱码，考虑操作系统和客户端浏览器默认编码        //判断服务器操作系统，本地开发使用windows        String os = System.getProperty("os.name");          if(os.toLowerCase().indexOf("windows") != -1){        fileName = new String(fileName.getBytes("GBK"), "ISO-8859-1");        }else{        //判断浏览器        String userAgent = request.getHeader("User-Agent").toLowerCase();                if(userAgent.indexOf("msie") > 0){                fileName = URLEncoder.encode(fileName, "ISO-8859-1");                }        }            //响应二进制流            response.setContentType("application/octet-stream");            response.reset();//清除response中的缓存            //根据网络文件地址创建URL              URL url = new URL(downLoadPath);              //获取此路径的连接              URLConnection conn = url.openConnection();              Long fileLength = conn.getContentLengthLong();//获取文件大小              //设置reponse响应头，真实文件名重命名，就是在这里设置，设置编码              response.setHeader("Content-Disposition",                      "attachment; filename=" + fileName);              response.setHeader("Content-Length", String.valueOf(fileLength));                bis = new BufferedInputStream(conn.getInputStream());//构造读取流              bos = new BufferedOutputStream(response.getOutputStream());//构造输出流              byte[] buff = new byte[1024];              int bytesRead;              //每次读取缓存大小的流，写到输出流              while (-1 != (bytesRead = bis.read(buff, 0, buff.length))) {                  bos.write(buff, 0, bytesRead);              }              response.flushBuffer();//将所有的读取的流返回给客户端          } catch (IOException e) {          logger.error("文件下载失败！", e);throw new CommonException("文件下载失败！");        }finally{        try{        if(null != bis){        bis.close();        }        if(null != bos){        bos.close();        }        }catch(IOException e){        logger.error("文件下载失败！", e);    throw new CommonException("文件下载失败！");        }        }        return null;    }