download.java

JAVA源码

/**
 * @(#)DownManager.java
 *
 *
 * @author 
 * @version 1.00 2008/6/6
 */
import java.io.*;
import java.net.*;
import java.util.*;

 class Download extends Observable implements Runnable {

   public static final int MAX_BUFFER_SIZE=1024;
   public static final String STATUSES[]={"downloading","paused","complete","cancelled","error"};
   public static final int DOWNLOADING=0;
   public static final int PAUSED=1;
   public static final int COMPLETE=2;
   public static final int CANCELLED=3;
   public static final int ERROR=4;
   private URL url;
   private int size;
   private int downloaded;  
   private int status;
   public Download(URL url){  
   	   this.url=url;
   	   size=-1;
   	   downloaded=0;
   	   status=DOWNLOADING;
   	   download();
   	}
   	
   	public String getUrl()
   	{
   		return url.toString();
   	}
   	
   	public int getSize()
   	{
   		return size;
   	}
   	
   	public float getProgress()
   	{
   		return ((float)downloaded/size)*100;
   	}
   	public int  getStatus()
   	{
   		return status;
   	}
   	
   	public void pause()
   	{
   		status=PAUSED;
   		stateChanged();
   	}
   	
   	public void resume()
   	{
   		status=DOWNLOADING;
   		stateChanged();
   		download();
   	}
   	
   	public void cancel()
   	{
   		status=CANCELLED;
   	    stateChanged();
   	    
   	}
   	
   	private void error()
   	{
   		status=ERROR;
   		stateChanged();
   	}
   	private void download()
   	{
   		Thread thread=new Thread(this);
   		thread.start(); 
   	}
   	
   	private String getFileName(){
   		String fileName=url.getFile();
   		return fileName.substring(fileName.lastIndexOf('/')+1);
   	}
   	
   	public void run(){
   		RandomAccessFile file=null;
   		InputStream stream =null;
   		try 
   		{
   			HttpURLConnection connection=(HttpURLConnection)url.openConnection();
   			connection.setRequestProperty("Range","byte="+downloaded+"-");
   			connection.connect();
   			if(connection.getResponseCode()/100!=2){
   				error();
   			}
   			int contentLength=connection.getContentLength();
   			if(contentLength<1){
   				error();
   			}
   			if(size==-1){
   				size=contentLength;
   				stateChanged();
   			}
    			file =new RandomAccessFile(getFileName(url),"rw");
   			file.seek(downloaded);
   			stream=connection.getInputStream();
   			while(status==DOWNLOADING){
   				byte[] buffer;
   				if(size-downloaded>MAX_BUFFER_SIZE ){
   					buffer=new byte[MAX_BUFFER_SIZE];
   					
   				}
   				else{
   					buffer=new byte[size-downloaded];
   				}
   				int read=stream.read(buffer);
   				if(read==-1)
   					break;
   				file.write(buffer,0,read);
   				downloaded+=read;
   				stateChanged();
   			}
   			if(status==DOWNLOADING){
   				status=COMPLETE;
   				stateChanged();
   			}
   			
   		}
   		catch(Exception e){
   			e.printStackTrace();
   		}
   		finally{
   			if(file!=null){
   				try{
   					file.close();
   				}catch(Exception e){}
   			}
   			if (stream!=null){
   				try{
   					stream.close();
   				}
   				catch(Exception e){}
   			}
   		}
   	}
   	
    private void stateChanged(){
    	setChanged();
    	notifyObservers();
    }  
}