package download;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
public class down {
/**
* @param args
*/
private static int threadCount = 3;
private static int blockSize;
private static String path = "http://mirrors.shu.edu.cn/apache/tomcat/tomcat-7/v7.0.91/bin/apache-tomcat-7.0.91.zip";
private static int currentRunThreadCount = 0;
public static void main(String[] args) {
try {
URL url = new URL(path);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(100 * 1000);
int code = connection.getResponseCode();
if(code == 200) {
int fileLength = connection.getContentLength();
RandomAccessFile randomAccessFile = new RandomAccessFile(new File(getFileName(path)), "rw");
randomAccessFile.setLength(fileLength);
blockSize = fileLength / threadCount;
for(int i = 0; i < threadCount; i ++) {
int startThread = i * blockSize;
int endThread = (i + 1) * blockSize - 1;
if( i == blockSize - 1) endThread = fileLength -1;
new DownloadThread(i, startThread, endThread).start();
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
public static class DownloadThread extends Thread {
private int threadId;
private int endThread;
private int startThred;
public DownloadThread(int threadId, int startThred, int endThread) {
this.threadId = threadId;
this.startThred = startThred;
this.endThread = endThread;
}
public void run() {
synchronized (DownloadThread.class) {
currentRunThreadCount += 1;
}
//分段请求网络连接，分段保存在本地
try {
System.err.println("理论线程:"+threadId+",开始位置:"+startThred+",结束位置:"+endThread);
URL url = new URL(path);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setRequestMethod("GET");
connection.setConnectTimeout(100 * 1000);
File file = new File(threadId+".txt");
if(file.exists()) { //是否断点
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
String lastPostion_str = bufferedReader.readLine();
startThred = Integer.parseInt(lastPostion_str);
bufferedReader.close();
}
//设置分段下载的头信息 Range:做分段
connection.setRequestProperty("Range", "bytes:"+startThred+"-" + endThread); //开始下载点
int code = connection.getResponseCode();
System.out.println(code);
if(code == 200) { //200:请求全部资源成功 206:代表部分资源请求成功
InputStream inputStream = connection.getInputStream();
System.out.println(getFileName(path));
RandomAccessFile randomAccessFile = new RandomAccessFile(new File(getFileName(path)), "rw");
randomAccessFile.seek(startThred);
byte[] buffer = new byte[1024*10];
int length = -1;
int total = 0;//记录下载的总量
System.err.println("实际线程:"+threadId+",开始位置:"+startThred+",结束位置:"+endThread);
while((length = inputStream.read(buffer)) != -1) {
randomAccessFile.write(buffer, 0, length);
total += length;
int currentThreadPostion = startThred + total;
RandomAccessFile randomAccessFile2 = new RandomAccessFile(file, "rwd");
randomAccessFile2.write(String.valueOf(currentThreadPostion).getBytes());
randomAccessFile2.close();
}
randomAccessFile.close();
inputStream.close();
System.err.println("线程:"+threadId+"下载完毕");
synchronized (DownloadThread.class) {
currentRunThreadCount -= 1;
if(currentRunThreadCount == 0){
for(int i = 0; i < threadCount; i ++) {
File file2 = new File(i+".txt");
// file2.delete();
}
}
}
}
} catch (Exception e) {
e.printStackTrace();
}
super.run();
}
}
public static String getFileName(String path) {
return path.substring(path.lastIndexOf("/")+1);
}
}
