url 断点续传

来源：互联网发布：程序员培训课程付费编辑：程序博客网时间：2024/06/08 07:14
通过url下载文件，中间服务器可能中断，需要断点续传 private void copyUrlPartly( URL url) throws IOException {        List<PartETag> partETags = new ArrayList<PartETag>();        long totalUplod = 0L;        int index = 1;        long remain = fileSize;        int retry = 0;            HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();        long fileSize = httpURLConnection.getContentLengthLong();       /*如果下载的size小于size那么，就重新请求连接*/        while (totalUplod < fileSize && retry < 5) {                      byte readBuffer[] = new byte[1024];                        HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();                       httpURLConnection.setRequestProperty("RANGE", "bytes="+totalUplod+"-");                        httpURLConnection.connect();                        InputStream stream = httpURLConnection.getInputStream();                        BufferedInputStream bis = new BufferedInputStream(stream);                        if(remain <= 0) {                break;            }                        while (remain > 0) {                              long partSize = 0L;                               File tmpFile = null;                               try {                                  /* 使用临时文件作为中转 */                                     tmpFile = File.createTempFile( "test", null);                   /* 将part拷贝到临时文件夹下面的临时文件 */                  partSize = downloadPart(bis, readBuffer, tmpFile);                  // 在这可以对tmpFile处理你 省略不写                   remain -= partSize;                  totalUplod += partSize;                                      retry = 0;                             } catch (Exception e) {                  retry++;                    logger.error("copyUrlPartly failed. ", e);                     break;                            } finally {                    if (null != tmpFile) {                        tmpFile.delete();                    }                }            }        }        }//将网上下载部分保存到临时文件tmpFile中private long downloadPart(BufferedInputStream bis, byte[] buffer, File tmpFile) throws Exception {        BufferedOutputStream bos = null;        long total = 0;        try {            bos = new BufferedOutputStream(new FileOutputStream(tmpFile));            int count;            while ((count = bis.read(buffer)) > 0) {                total += count;                bos.write(buffer, 0, count);            }        } finally {            try {                if (null != bos) {                    bos.close();                }            } catch (Exception e) {                logger.debug("IoCloseException", e);            }        }        return total;    }Range头域  　　Range头域可以请求实体的一个或者多个子范围。例如，  　　表示头500个字节：bytes=0-499  　　表示第二个500字节：bytes=500-999  　　表示最后500个字节：bytes=-500  　　表示500字节以后的范围：bytes=500-  　　第一个和最后一个字节：bytes=0-0,-1  　　同时指定几个范围：bytes=500-600,601-999
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