Java 下载支持断点续传服务端，java断点续传,private void

Java 下载支持断点续传服务端，java断点续传,private void

private void downFile(HttpServletResponse response, HttpServletRequest request, String location){    BufferedInputStream bis = null;    try {        File file = new File(location);        if (file.exists()) {            long p = 0L;            long toLength = 0L;            long contentLength = 0L;            int rangeSwitch = 0; // 0,从头开始的全文下载；1,从某字节开始的下载（bytes=27000-）；2,从某字节开始到某字节结束的下载（bytes=27000-39000）            long fileLength;            String rangBytes = "";            fileLength = file.length();            // get file content            InputStream ins = new FileInputStream(file);            bis = new BufferedInputStream(ins);            // tell the client to allow accept-ranges            response.reset();            response.setHeader("Accept-Ranges", "bytes");            // client requests a file block download start byte            String range = request.getHeader("Range");            if (range != null &amp;&amp; range.trim().length() > 0 &amp;&amp; !"null".equals(range)) {                response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT);                rangBytes = range.replaceAll("bytes=", "");                if (rangBytes.endsWith("-")) {  // bytes=270000-                    rangeSwitch = 1;                    p = Long.parseLong(rangBytes.substring(0, rangBytes.indexOf("-")));                    contentLength = fileLength - p;  // 客户端请求的是270000之后的字节（包括bytes下标索引为270000的字节）                } else { // bytes=270000-320000                    rangeSwitch = 2;                    String temp1 = rangBytes.substring(0, rangBytes.indexOf("-"));                    String temp2 = rangBytes.substring(rangBytes.indexOf("-") + 1, rangBytes.length());                    p = Long.parseLong(temp1);                    toLength = Long.parseLong(temp2);                    contentLength = toLength - p + 1; // 客户端请求的是 270000-320000 之间的字节                }            } else {                contentLength = fileLength;            }            // 如果设设置了Content-Length，则客户端会自动进行多线程下载。如果不希望支持多线程，则不要设置这个参数。            // Content-Length: [文件的总大小] - [客户端请求的下载的文件块的开始字节]            response.setHeader("Content-Length", new Long(contentLength).toString());            // 断点开始            // 响应的格式是:            // Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小]            if (rangeSwitch == 1) {                String contentRange = new StringBuffer("bytes ").append(new Long(p).toString()).append("-")                        .append(new Long(fileLength - 1).toString()).append("/")                        .append(new Long(fileLength).toString()).toString();                response.setHeader("Content-Range", contentRange);                bis.skip(p);            } else if (rangeSwitch == 2) {                String contentRange = range.replace("=", " ") + "/" + new Long(fileLength).toString();                response.setHeader("Content-Range", contentRange);                bis.skip(p);            } else {                String contentRange = new StringBuffer("bytes ").append("0-")                        .append(fileLength - 1).append("/")                        .append(fileLength).toString();                response.setHeader("Content-Range", contentRange);            }            String fileName = file.getName();            response.setContentType("application/octet-stream");            response.addHeader("Content-Disposition", "attachment;filename=" + fileName);            OutputStream out = response.getOutputStream();            int n = 0;            long readLength = 0;            int bsize = 1024;            byte[] bytes = new byte[bsize];            if (rangeSwitch == 2) {                // 针对 bytes=27000-39000 的请求，从27000开始写数据                                    while (readLength <= contentLength - bsize) {                    n = bis.read(bytes);                    readLength += n;                    out.write(bytes, 0, n);                }                if (readLength <= contentLength) {                    n = bis.read(bytes, 0, (int) (contentLength - readLength));                    out.write(bytes, 0, n);                }                               } else {                while ((n = bis.read(bytes)) != -1) {                    out.write(bytes,0,n);                                                                      }                               }            out.flush();            out.close();            bis.close();        } else {            if (logger.isDebugEnabled()) {                logger.debug("Error: file " + location + " not found.");            }                        }    } catch (IOException ie) {        // 忽略 ClientAbortException 之类的异常    } catch (Exception e) {        logger.error(e);    }}