Java 下载支持断点续传

[Java]代码，服务器端实现

01	File file = new File(location);

02	if (file.exists()) {

03	long p = 0;

04	long fileLength;

05	fileLength = file.length();

06

07	// get file content

08	InputStream ins = new FileInputStream(file);

09	bis = new BufferedInputStream(ins);

10

11	// tell the client to allow accept-ranges

12	response.reset();

13	response.setHeader("Accept-Ranges", "bytes");

14

15	// client requests a file block download start byte

16	if (request.getHeader("Range") != null) {

17	response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT);

18	p = Long.parseLong(request.getHeader("Range")

19	.replaceAll("bytes=", "")

20	.replaceAll("-", "")

21

);

22

}

23	// support multi-threaded download

24	// respone format:

25	// Content-Length:[file size] - [client request start bytes from file block]

26	response.setHeader("Content-Length", new Long(fileLength - p).toString());

27

28	if (p != 0) {

29

// 断点开始

30	// 响应的格式是:

31	// Content-Range: bytes [文件块的开始字节]-[文件的总大小 - 1]/[文件的总大小]

32	String contentRange = new StringBuffer("bytes ")

33	.append(new Long(p).toString())

34	.append("-")

35	.append(new Long(fileLength - 1).toString())

36	.append("/")

37	.append(new Long(fileLength).toString())

38	.toString();

39	response.setHeader("Content-Range", contentRange);

40	// pointer move to seek

41	bis.skip(p);

42

}

43

44	String fileName = file.getName();

45	response.addHeader("Content-Disposition", "attachment;filename=" + fileName);

46

47	while ((size = bis.read(buf)) != -1) {

48	response.getOutputStream().write(buf,0,size);

49	response.getOutputStream().flush();

50

}

51	bis.close();

[代码] 客户端下载测试

 

01	public class TestDownload {

02

03

/**

04	* @param args

05

*/

06	public static void main(String[] args) {

07	// TODO Auto-generated method stub

08	HttpURLConnection httpURLConnection = null;

09	URL url = null;

10	BufferedInputStream bis = null;

11	byte[] buf = new byte[10240];

12	int size = 0;

13	String fileName = "aaa.zip";

14	String filePath = "C:\\Users\\Desktop";

15	String remoteUrl = "http://127.0.0.1:8080/down.zip";

16

17

// 检查本地文件

18	RandomAccessFile rndFile = null;

19	File file = new File(filePath + "\\" + fileName);

20	long remoteFileSize = getRemoteFileSzie(remoteUrl);

21	long nPos = 0;

22

23	if (file.exists()) {

24	long localFileSzie = file.length();

25	if (localFileSzie < remoteFileSize) {

26	System.out.println("文件续传...");

27	nPos = localFileSzie;

28

} else {

29	System.out.println("文件存在，重新下载...");

30	file.delete();

31

try {

32	file.createNewFile();

33	} catch (Exception e) {

34	// TODO: handle exception

35	e.printStackTrace();

36

}

37

}

38

39

} else {

40

// 建立文件

41

try {

42	file.createNewFile();

43	} catch (Exception e) {

44	// TODO: handle exception

45	e.printStackTrace();

46

}

47

}

48

49

// 下载文件

50

try {

51	url = new URL(remoteUrl);

52	httpURLConnection = (HttpURLConnection)url.openConnection();

53	// 设置User-Agent

54	httpURLConnection.setRequestProperty("User-Agent", "Net");

55

// 设置续传开始

56	httpURLConnection.setRequestProperty("Range", "bytes=" + nPos + "-");

57

// 获取输入流

58	bis = new BufferedInputStream(httpURLConnection.getInputStream());

59	rndFile = new RandomAccessFile(filePath + "\\" + fileName, "rw");

60	rndFile.seek(nPos);

61	int i = 0;

62	while ((size = bis.read(buf)) != -1) {

63	//if (i > 500) break;

64	rndFile.write(buf, 0, size);

65

66

i++;

67

}

68	System.out.println("i=" + i);

69	httpURLConnection.disconnect();

70	} catch (Exception e) {

71	// TODO: handle exception

72	e.printStackTrace();

73

}

74

}

75

76	public static long getRemoteFileSzie(String url) {

77	long size = 0;

78

try {

79	HttpURLConnection httpUrl = (HttpURLConnection)(new URL(url)).openConnection();

80	size = httpUrl.getContentLength();

81	httpUrl.disconnect();

82	} catch (Exception e) {

83	// TODO: handle exception

84	e.printStackTrace();

85

}

86	return size;

87

}

88

}