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 | // 斷點開始 |
30 | // 響應的格式是: |
31 | // Content-Range: bytes [文件塊的開始字節(jié)]-[文件的總大小 - 1]/[文件的總大小] |
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(); |
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 | // 檢查本地文件 |
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("文件續(xù)傳..."); |
27 | nPos = localFileSzie; |
28 | } else { |
29 | System.out.println("文件存在，重新下載..."); |
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 | // 下載文件 |
50 | try { |
51 | url = new URL(remoteUrl); |
52 | httpURLConnection = (HttpURLConnection)url.openConnection(); |
53 | // 設置User-Agent |
54 | httpURLConnection.setRequestProperty("User-Agent", "Net"); |
55 | // 設置續(xù)傳開始 |
56 | httpURLConnection.setRequestProperty("Range", "bytes=" + nPos + "-"); |
57 | // 獲取輸入流 |
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 | } |
