1 import java.io.ByteArrayOutputStream;
2 import java.io.InputStream;
3
4 public class StreamTool {
5 /**
6 * 把一个inputstream里面的内容转化成一个byte[]
7 */
8 public static byte[] getBytes(InputStream is) throws Exception {
9 ByteArrayOutputStream bos = new ByteArrayOutputStream();
10 byte[] buffer = new byte[1024];
11 int len = 0;
12 while ((len = is.read(buffer)) != -1) {
13 bos.write(buffer, 0, len);
14 }
15 is.close();
16 bos.flush();
17 byte[] result = bos.toByteArray();
18 System.out.println(new String(result));
19 return result;
20 }
21 }
1 import java.io.File;
2 import java.io.FileInputStream;
3 import java.io.FileOutputStream;
4 import java.io.InputStream;
5 import java.io.RandomAccessFile;
6 import java.net.HttpURLConnection;
7 import java.net.URL;
8
9 public class TestDownload {
10 public static final String path = "http://192.168.1.100:8080/aaa.exe";
11
12 public static void main(String[] args) throws Exception {
13 URL url = new URL(path);
14 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
15 conn.setRequestMethod("GET");
16 conn.setConnectTimeout(5000);
17 conn.setRequestProperty("User-Agent",
18 "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
19 int code = conn.getResponseCode();
20 if (code == 200) {
21 int len = conn.getContentLength();
22 RandomAccessFile file = new RandomAccessFile(
23 "C:/Users/DELL/Desktop/" + getFilenName(path), "rwd");
24 // 1.设置本地文件大小跟服务器的文件大小一致
25 file.setLength(len);
26
27 // 2 .假设开启3 个线程
28 int threadnumber = 3;
29 int blocksize = len / threadnumber;
30 /**
31 * 线程1 0~ blocksize 线程2 1*bolocksize ~ 2*blocksize 线程3 2 *blocksize ~
32 * 文件末尾
33 */
34 for (int i = 0; i < threadnumber; i++) {
35 int startposition = i * blocksize;
36 int endpositon = (i + 1) * blocksize;
37 if (i == (threadnumber - 1)) {
38 // 最后一个线程
39 endpositon = len;
40 }
41 DownLoadTask task = new DownLoadTask(
i, path, startposition,endpositon);
43 task.start();
44 }
45 }
46 }
47
48 public static String getFilenName(String path) {
49 int start = path.lastIndexOf("/") + 1;
50 return path.substring(start, path.length());
51 }
52
53 }
54
55 class DownLoadTask extends Thread {
56 public static final String path = "http://192.168.1.100:8080/aaa.exe";
57 int threadid;
58 String filepath;
59 int startposition;
60 int endpositon;
61
62 public DownLoadTask(int threadid, String filepath,
int startposition, int endpositon) {
64 this.threadid = threadid;
65 this.filepath = filepath;
66 this.startposition = startposition;
67 this.endpositon = endpositon;
69 }
70
71 @Override
72 public void run() {
73 try {
74 File postionfile = new File(threadid + ".txt");
75 URL url = new URL(filepath);
76 HttpURLConnection conn = (HttpURLConnection) url.openConnection();
77 System.out.println("线程" + threadid + "正在下载 " + "开始位置 : "
78 + startposition + "结束位置 " + endpositon);
79
80 // 断点操作
81 if (postionfile.exists()) {
82 FileInputStream fis = new FileInputStream(postionfile);
83 byte[] result = StreamTool.getBytes(fis);
84 int newstartposition = Integer.parseInt(new String(result));
85 if (newstartposition > startposition) { // 如果新的位置 > 开始位置。
86 startposition = newstartposition;
87 }
88 }
89
90 // "Range", "bytes=2097152-4194303")
91 conn.setRequestProperty("Range", "bytes=" + startposition + "-"
92 + endpositon);
93 conn.setRequestMethod("GET");
94 conn.setConnectTimeout(5000);
95 conn.setRequestProperty("User-Agent",
96 "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
97 InputStream is = conn.getInputStream();
98 RandomAccessFile file = new RandomAccessFile(
99 "C:/Users/DELL/Desktop/" + getFilenName(path), "rwd");
100 // 设置 数据从文件哪个位置开始写
101 file.seek(startposition);
102 byte[] buffer = new byte[1024];
103 int len = 0;
104
105 // 代表当前读到的服务器数据的位置 ,同时这个值已经存储的文件的位置
106 int currentPostion = startposition;
107
108 // 创建一个文件对象 ,记录当前某个文件的下载位置
109 while ((len = is.read(buffer)) != -1) {
110 file.write(buffer, 0, len);
111
112 currentPostion += len;
113 // 需要把currentPostion 信息给持久化到存储设备
114 String position = currentPostion + "";
115 System.out.println("线程 .." + threadid + "....开始位置..."
116 + startposition + "..当前位置..." + currentPostion
117 + "...结束位置...." + endpositon);
118 FileOutputStream fos = new FileOutputStream(postionfile);
119 fos.write(position.getBytes());
120 fos.flush();
121 fos.close();
122 }
123 file.close();
124 System.out.println("线程" + threadid + "下载完毕");
125 // 当线程下载完毕后 把文件删除掉
126 if (postionfile.exists()) {
127 postionfile.delete();
128 }
129 } catch (Exception e) {
130 e.printStackTrace();
131 }
132 super.run();
133 }
134
135 public static String getFilenName(String path) {
136 int start = path.lastIndexOf("/") + 1;
137 return path.substring(start, path.length());
138 }
139
140 }
1 public class test1 {
2 public static void main(String[] args) throws Exception {
3 RandomAccessFile file = new RandomAccessFile("haha.txt", "rwd");
4 file.setLength(1024 * 1024);
5 }
6 }
