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);   
        }   
    }   
}