filedown.java

Java写的下载文件程序

/* FileDown.java */ 

import javax.swing.*;
import java.io.*;
import java.net.*; 
import java.util.*;

public class FileDown extends Thread
{
  //定义私有成员对象
  private String urlString=null;      //网络路径名称字符串
  private String fileString=null;     //保存文件名称字符串
  private int priorityInt=0;          //下载线程及其子线程的优先权
  private int threadnumInt=0;         //下载子线程数
  private long fileLong=0;            //下载文件长度 
  private long[] startposLong;        //下载子线程开始位置数组
  private long[] endposLong;          //下载子线程结束位置数组 
  private FileSplitDown[] filesplit=null;  //下载子线程对象数组 
  private boolean stopBoolean = false;//下载停止标志 
  private File tempFile=null;         //保存文件下载过程信息的临时文件 

  //构造函数
  public FileDown(Vector info) throws IOException 
  { 
    urlString=info.elementAt(1).toString();
    fileString=info.elementAt(2).toString();
    priorityInt=Integer.parseInt(info.elementAt(4).toString());
    threadnumInt=Integer.parseInt(info.elementAt(5).toString());
    setPriority(priorityInt);
    tempFile = new File(fileString+".dat");
    if(tempFile.exists()) read_pos(); //从临时文件中读取下载位置
    else //是第一次下载,从网络路径取得文件的总长度,并分配给各个子线程
    { 
     startposLong = new long[threadnumInt]; 
     endposLong = new long[threadnumInt];
     fileLong = getFileSize(); 
     if(fileLong == -1) 
     { 
      System.err.println("File Length is not known!");
      JOptionPane.showMessageDialog(null,"未知的文件长度,发生错误,"+
             "下载线程将停止.","错误...",JOptionPane.ERROR_MESSAGE);
      stopBoolean=true;
     }
     else if(fileLong == -2) 
     { 
      System.err.println("File is not access!");
      JOptionPane.showMessageDialog(null,"文件无法访问,发生错误,"+
            "下载线程将停止.","错误...",JOptionPane.ERROR_MESSAGE);
      stopBoolean=true;
     }
     else 
     { 
      for(int i=0;i<threadnumInt;i++) 
        startposLong[i] = (long)(i*(fileLong/threadnumInt)); 
      for(int i=0;i<threadnumInt-1;i++) 
        endposLong[i] = startposLong[i+1]; 
      endposLong[threadnumInt-1] = fileLong; 
     } 
    }
    if(fileLong>0)
    {
     filesplit = new FileSplitDown[threadnumInt];
     for(int i=0;i<threadnumInt;i++) 
     { 
      filesplit[i] = new FileSplitDown(urlString,fileString,
                startposLong[i],endposLong[i],i,priorityInt);
      System.out.println("Thread " + i + " , startpos = " +
           startposLong[i] + ", endpos = " + endposLong[i]);
      filesplit[i].start(); 
     }
    }
  }//结束构造函数FileDown() 

  //下载文件线程的主体
  public void run()
  {  
   try
   { //等待子线程结束
    boolean breakBoolean = false; //是否结束while循环
    while ((!stopBoolean) && (!breakBoolean))
    { 
     write_pos(); 
     Thread.sleep(500);
     breakBoolean = true;
     for(int i=0;i<threadnumInt;i++) 
      if(!filesplit[i].getSplitDown()) 
        //寻找未结束的子线程,如果有一个子线程未结束,则下载线程就不能结束
      { breakBoolean = false; break; } 
      else if((filesplit[i].getStart()-startposLong[i])<250) 
        //如果某一个子线程的下载流量过小(低于500byte/sec),则自动断开结束
        //该子线程,并重新建立一个子线程
      {
       filesplit[i].splitDownStop();
       filesplit[i]=null;
       filesplit[i]=new FileSplitDown(urlString,fileString,
               startposLong[i],endposLong[i],i,priorityInt);
       filesplit[i].start();
      }
    }  
    if(breakBoolean)
    {
     tempFile.delete();
     System.out.println("文件下载结束！");
    }
   }  
   catch(Exception e){e.printStackTrace (); } 
  }//结束函数run() 

  /*以下部分是公共成员函数*/

  //停止文件下载 
  public void downStop() 
  { 
   stopBoolean = true; 
   for(int i=0;i<threadnumInt;i++) 
     filesplit[i].splitDownStop(); 
  } 

  //取得文件下载的进度(0--100)
  public int getProgress()
  {
   long total=0;
   try
   {
    for( int i=0;i<threadnumInt;i++)//计算还未下载的字节数
     total=total+filesplit[i].getEnd()-filesplit[i].getStart(); 
   }
   catch (NullPointerException e){ return 0;}
   return (int)(100-(((double)total)/((double)fileLong))*100);
  }

  //取得文件下载线程当前的状态
  public String getStatus()
  {
   if(stopBoolean) return "停止";
   else return "运行";
  }

  //取得下载文件的总长度
  public long getFileLength()
  {
   return fileLong;
  }

  //取得下载文件的网络路径
  public String getURL()
  {
    return urlString;
  }

  /*以下部分是私有成员函数*/

  //获得文件长度 
  private long getFileSize() 
  { 
   long lengthLong = -1; 
   try
   {
    URL url = new URL(urlString); 
    HttpURLConnection httpConnection;
    httpConnection = (HttpURLConnection)url.openConnection ();
    httpConnection.setRequestProperty("User-Agent","DDXC"); 
    int responseInt=httpConnection.getResponseCode(); 
    if(responseInt>=400) 
    { 
     processErrorCode(responseInt); 
     return -2; //-2 表示对文件操作没有权限 
    } 
    String headerString; 
    for(int i=1;;i++) 
    { 
     headerString=httpConnection.getHeaderFieldKey(i); 
     if(headerString==null)  break;
     if(headerString.equals("Content-Length")) 
     { 
      lengthLong = Long.parseLong(httpConnection.getHeaderField
        (headerString));
      break; 
     } 
    } 
   } 
   catch(IOException e){ e.printStackTrace (); } 
   catch(Exception e)  { e.printStackTrace (); } 
   return lengthLong; 
  }//结束私有成员函数getFileSize() 

  //保存下载信息（文件指针位置） 
  private void write_pos() 
  { 
   try
   {
    DataOutputStream output;
    output = new DataOutputStream(new FileOutputStream(tempFile));
    output.writeInt(threadnumInt); 
    for(int i=0;i<threadnumInt;i++) 
    { 
     output.writeLong((startposLong[i]=filesplit[i].getStart())); 
     output.writeLong((endposLong[i]=filesplit[i].getEnd())); 
    }
    output.writeLong(fileLong);
    output.close(); 
   } 
   catch(IOException e){ e.printStackTrace (); } 
   catch(Exception e)  { e.printStackTrace (); } 
  }//结束私有成员函数write_pos() 

  //读取保存的下载信息（文件指针位置） 
  private void read_pos() 
  { 
   try
   {
    DataInputStream input;
    input = new DataInputStream(new FileInputStream(tempFile));
    threadnumInt = input.readInt(); 
    startposLong = new long[threadnumInt]; 
    endposLong = new long[threadnumInt]; 
    for(int i=0;i<threadnumInt;i++) 
    { 
     startposLong[i] = input.readLong(); 
     endposLong[i] = input.readLong(); 
    } 
    fileLong=input.readLong();
    input.close();
   } 
   catch(IOException e) { e.printStackTrace (); } 
   catch(Exception e)   { e.printStackTrace (); } 
  }//结束私有成员函数read_pos() 

  //显示错误代码
  private void processErrorCode(int nErrorCode)
  { 
   System.err.println("Error Code : " + nErrorCode); 
  } 

}//结束类FileDown