- 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 && range.trim().length() > 0 && !"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);
- }
- }
- //该片段来自于http://www.codesnippet.cn/detail/140720149962.html
来源: http://www.codesnippet.cn/detail/140720149962.html