downfilesplitter.java

用多线程下载URL定位的文件,主要供学习java多线程的人和HTTP协议的人参考

import java.io.*;
import java.net.*;
import javax.swing.JTextArea;
/*
 * DownFileSplitter.java
 *
 * Created on 2006年12月11日, 下午1:25
 *
 * To change this template, choose Tools | Template Manager
 * and open the template in the editor.
 */

/**
 *
 * @author Administrator
 */
//下载指定的段
/**********************************************************************************************/
/*类设计：
 *类名：DownFileSplitter;
 *功能：实现对指定段文件数据的下载;
 *方法：
 *      构造方法DownFileSplitter(String localFilePath,
 *                               String stringURL,int startPos,int endPos);
 *      线程方法run();
 *      下载数据段方法getPartFile();
 *
 *   
 *
 *
 */
/************************************************************************************************/
public class DownFileSplitter extends Thread{
    String localFilePath;
    String stringURL; 
    boolean bDownOver=false;
    JTextArea messageJTextArea;
    int startPos;
    int endPos;
    int mark;
    /** Creates a new instance of DownFileSplitter */
    //构造方法，初始化属性
    public DownFileSplitter(String localFilePath,
            String stringURL,int startPos,int endPos,JTextArea messageJTextArea,int mark) {
        this.localFilePath=localFilePath;
        this.stringURL=stringURL;
        this.messageJTextArea=messageJTextArea;        
        this.startPos=startPos;
        this.endPos=endPos;
        this.mark=mark;
    }
    public  void getPartFile(){
        URL url;
        HttpURLConnection hURL;
        RandomAccessFile file;       
        int partLength=(int)(endPos-startPos);
        //System.out.println("文件段长度："+partLength);
        int length=0;
        try {
            url=new URL(stringURL);
            hURL=(HttpURLConnection) url.openConnection();
            String sProperty="bytes="+startPos+"-";
            //System.out.println("文件开始下载位置："+sProperty);
            hURL.setRequestProperty("RANGE",sProperty);
            BufferedInputStream bIn=new BufferedInputStream(hURL.getInputStream());
            byte[] buf=new byte[1024];
            int len;
            file=new  RandomAccessFile(localFilePath,"rw");
            file.seek(startPos);
            while((len=bIn.read(buf))!=-1){
                if(len>partLength-length){
                    len=partLength-length;
                }
                file.write(buf,0,len);
                //System.out.println(len);
                length+=len;
                if(length>=partLength){
                    messageJTextArea.append("\n子线程"+mark+"下载完毕！");
                    hURL.disconnect();                   
                    file.close();
                    break;
                }
                bDownOver=true;
            }
            //System.out.println("\n子线程"+mark+"下载文件长度："+length);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    public void run(){
        //System.out.println("\n子线程"+mark+"下载中.....");
        messageJTextArea.append("\n子线程"+mark+"下载中......");
        getPartFile();        
    }
    //供此类测试用
//    public static void main(String[] args) {
//        String urlString=new String("http://www.zhouyunhai.com/book/whomovedmycheese.exe");
//        String filePart=new String("H:\\2.exe");
//        DownFileSplitter downFile0=new DownFileSplitter(filePart,urlString,0,1024);
//        DownFileSplitter downFile1=new DownFileSplitter(filePart,urlString,1024,2048);
//        DownFileSplitter downFile2=new DownFileSplitter(filePart,urlString,2048,1000000);
//        downFile0.start();
//        downFile1.start();
//        downFile2.start(); 
//    }
    
}