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DownloadFile.java
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100 lines (97 loc) · 2.89 KB
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package com.cWww.homework;
import java.io.BufferedInputStream;
import java.io.EOFException;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
/**
* 用于下载用的线程
* @author Administrator
*
*/
public class DownloadFile extends Thread{
//下载地址
private String urlStr;
//开始的下载点
private long startPoint;
//结束的下载点
private long endPoint;
//下载到本地的目录
private File file;
public DownloadFile(String urlStr, long startPoint, long endPoint, File file) {
super();
this.urlStr = urlStr;
this.startPoint = startPoint;
this.endPoint = endPoint;
this.file = file;
}
@Override
public void run() {
BufferedInputStream bis = null;
RandomAccessFile raf = null;
RandomAccessFile raf_read = null;
RandomAccessFile raf_write = null;
long seekPoint = 0;
//每一个流都可以创建自己的伴随文件
File f = new File(file,this.getName()+".txt");
try {
URL url = new URL(urlStr);
HttpURLConnection http = (HttpURLConnection)url.openConnection();
int code = http.getResponseCode();
if(code == HttpURLConnection.HTTP_OK){
//网络响应10s
http.setReadTimeout(10000);
//必须要先创建write，不然后面的read读不到文件会出现异常
raf_write = new RandomAccessFile(f, "rw");
raf_read = new RandomAccessFile(f, "r");
raf_read.seek(0);
try {
seekPoint = raf_read.readLong(); //用于对文件中的寻址位置进行读取
} catch(EOFException e){
seekPoint = startPoint;
}
InputStream is = http.getInputStream();
//创建输入输出流（对流进行包装）
bis = new BufferedInputStream(is);
raf = new RandomAccessFile(new File(file,urlStr.substring(urlStr.lastIndexOf("/"))),"rw");
//对于输入输出流的寻址！
bis.skip(seekPoint);
raf.seek(seekPoint);
byte[] b = new byte[1024];
int len = 0;
System.out.println(Thread.currentThread().getName()+"开始拷贝");
while((len = bis.read(b)) != -1 && startPoint <= endPoint){
startPoint += len;
raf.write(b,0,len);
raf_write.seek(0);
raf_write.writeLong(startPoint);//将实际拷贝长度放入伴随文件中
try {
//方便看到文件的拷贝进度（其实没有什么实际的用处）
sleep(200);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName()+"完成拷贝");
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally{
try {
if(raf!=null){raf.close();}
if(bis!=null){bis.close();}
if(raf_read!=null){raf_read.close();}
if(raf_write!=null){raf_write.close();}
f.delete();//当最后关闭了流以后对创建的文件进行删除
} catch (IOException e) {
e.printStackTrace();
}
}
}
}