1 importjava.io.InputStream;2 importjava.io.RandomAccessFile;3 importjava.net.HttpURLConnection;4 importjava.net.URL;5
6 public classDemo {7 public static String path = "http://softdownload.hao123.com/hao123-soft-online-bcs/soft/Y/2013-07-18_YoudaoDict_baidu.alading.exe";
8 public static int threadCount = 3;9 public static void main(String[] args) throwsException{10 //1.连接服务器，获取一个文件，获取文件的长度，在本地创建一个跟服务器一样大小的临时文件
11 URL url = newURL(path);12 HttpURLConnection conn =(HttpURLConnection)url.openConnection();13 conn.setConnectTimeout(5000);14 conn.setRequestMethod("GET");15 int code =conn.getResponseCode();16 if (code == 200) {17 //服务器端返回的数据的长度，实际上就是文件的长度
18 int length =conn.getContentLength();19 System.out.println("文件总长度："+length);20 //在客户端本地创建出来一个大小跟服务器端一样大小的临时文件
21 RandomAccessFile raf = new RandomAccessFile("setup.exe", "rwd");22 //指定创建的这个文件的长度
23 raf.setLength(length);24 raf.close();25 //假设是3个线程去下载资源。26 //平均每一个线程下载的文件大小.
27 int blockSize = length /threadCount;28 for (int threadId = 1; threadId <= threadCount; threadId++) {29 //第一个线程下载的开始位置
30 int startIndex = (threadId - 1) *blockSize;31 int endIndex = threadId * blockSize - 1;32 if (threadId == threadCount) {//最后一个线程下载的长度要稍微长一点
33 endIndex =length;34 }35 System.out.println("线程："+threadId+"下载:---"+startIndex+"--->"+endIndex);36 newDownLoadThread(path, threadId, startIndex, endIndex).start();37 }38
39 }else{40 System.out.printf("服务器错误!");41 }42 }43
44
49 public static class DownLoadThread extendsThread{50 private intthreadId;51 private intstartIndex;52 private intendIndex;53
59 public DownLoadThread(String path, int threadId, int startIndex, intendIndex) {60 super();61 this.threadId =threadId;62 this.startIndex =startIndex;63 this.endIndex =endIndex;64 }65
66 @Override67 public voidrun() {68 try{69 URL url = newURL(path);70 HttpURLConnection conn =(HttpURLConnection)url.openConnection();71 conn.setConnectTimeout(5000);72 conn.setRequestMethod("GET");73 //重要:请求服务器下载部分文件 指定文件的位置
74 conn.setRequestProperty("Range", "bytes="+startIndex+"-"+endIndex);75 //从服务器请求全部资源返回200 ok如果从服务器请求部分资源 返回 206 ok
76 int code =conn.getResponseCode();77 System.out.println("code:"+code);78 InputStream is = conn.getInputStream();//已经设置了请求的位置，返回的是当前位置对应的文件的输入流
79 RandomAccessFile raf = new RandomAccessFile("setup.exe", "rwd");80 //随机写文件的时候从哪个位置开始写
81 raf.seek(startIndex);//定位文件
82
83 int len = 0;84 byte[] buffer = new byte[1024];85 while ((len = is.read(buffer)) != -1) {86 raf.write(buffer, 0, len);87 }88 is.close();89 raf.close();90 System.out.println("线程："+threadId+"下载完毕");91 } catch(Exception e) {92 e.printStackTrace();93 }94 }95
96 }97 }