java实现断点续传

/**      
 * @{#} MainThreadDownFile.java 
 * Create on 2009-6-17 下午11:00:14   
 *   
 * @author 何明   
 * @version 1.0 
 *
 * Copyright (c) 2007 by GTT.      
 */

package com.down;

import java.io.File;

import com.common.Common;
import com.common.ExceptionManager;


public class MainThreadDownFile{
	
	private String url;
	private String localsavePath;
	private String localsaveName;
	private int threadNum;
	private static String tempStoreDirectory;//临时文件路径
	private long eachThreadSzie;//平均每个线程获取文件的大小
	boolean isDownStop=false;
	private int entid;
	
	public MainThreadDownFile(int entid,String url,String savePath,String saveName,int threadNum) {
		this.entid=entid;
		this.url=url;
		this.localsavePath=savePath;
		this.localsaveName=saveName;
		this.threadNum=threadNum;
		if(!createDirectory(localsavePath)){   //创建存放附件的地址
			Common.WriteLog("创建文件失败！");
			return;
		}
	}
	
	/**创建存放临时文件的临时文件夹*/
	private String getTempStoreDirectory(String tempDirctoryName){
        String tempDirctory = localsavePath +"\\"+ tempDirctoryName;
        String tNum = "";
        do{
            tempDirctory = tempDirctory + tNum;
            File file = new File(tempDirctory);
            if(file.exists()) tNum = "0";
            else return tempDirctory;
        } while(true);
    }
	
	/**判断是否有存放附件文件夹，如果没有就创建*/
	private boolean createDirectory(String localFileAddress){
		try{
			File file = new File(localFileAddress);
			if(!file.exists())
				file.mkdir();
		}catch(Exception e){
			e.printStackTrace();
            return false;
        }   
        return true;
    }
	
	public void getEachThreadFileSize(long size){
		eachThreadSzie=size/threadNum;
	}
	
	public boolean checkExistTPFile(){
        File file = new File(tempStoreDirectory);
        String fileList[] = file.list();
        if(fileList.length > 0){
            for(int i = 0; i < fileList.length; i++)
                if(fileList[i].indexOf(".tp") > 0)
                    return true;
        } 
        return false;
    }
	
	public void init(NetManager nm) throws ExceptionManager{		
		try{
			if(nm.getCode()==200){
				String tempDirctoryName="tmp";
				DownInfoWriteXml diwx=new DownInfoWriteXml(localsavePath);
				String localSaveAddress=diwx.downFileExist(url);     //获取临时附件地址
				if(localSaveAddress!=null){
					this.tempStoreDirectory=localSaveAddress;			
				}else{
					synchronized(this){
						tempStoreDirectory=getTempStoreDirectory(tempDirctoryName);
						createDirectory(tempStoreDirectory);
						diwx.addOneDownRecord(url, tempStoreDirectory);
						diwx.saveChange();
		            }
				}
				
				long filesize=nm.getFileSize();
				String filename=Common.getSuffixName(nm.getUrlFileName(),"/");
				String tempThreadfileName=tempStoreDirectory + "\\" + filename + ".part";
				getEachThreadFileSize(filesize);
				
				SingleThreadDownFile[] stdf=new SingleThreadDownFile[threadNum];
				long startPos=0L,endPos=0L;
				for(int i=1;i<=threadNum;i++){
					if(i>1) startPos+=eachThreadSzie;
					endPos=startPos+eachThreadSzie;
					DownInfo di=new DownInfo(i,url,startPos,endPos);
					stdf[i-1]=new SingleThreadDownFile(tempThreadfileName+i);
					stdf[i-1].setDi(di);
					stdf[i-1].start();
				}
				
				String str[]=new String[threadNum];
				boolean isStop=true;
				DownState ds=new DownState(filesize);
				while(isStop){					
					int n=0;
					long fsize=0L;
					long totalsize=0L;
					for(int i=1;i<=threadNum;i++){
						if(stdf[i-1].isAlive())
							fsize += stdf[i-1].downPace;
						else n++;
						long tsize=new Long(stdf[i-1].downSize);
						if(tsize==0){
							totalsize += Common.FileSize(tempThreadfileName+i);
						}else{
							totalsize += tsize;
						}
					}
					if(n==threadNum) isStop=false;
					ds.updateDownSize(fsize,totalsize);
					ds.init(isStop);
				}
				if(!checkExistTPFile()&&!isStop){
					FileCombination fc=new FileCombination(url,tempStoreDirectory,localsavePath,localsaveName);
					fc.init();
					isDownStop=true;
				}
			}else{
				Common.WriteLog(nm.getHttpMessage(nm.getCode()));
			}
		}catch(Exception e){
			throw new ExceptionManager(entid,"出现异常",e);
		}
	}
}