downloadthread.java

一个网络上传下载器

package DownloadManager;

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

/**
 this class create thread to start downloading.
 @author Liu Yu Yang
 */
public class DownloadThread 
        //extends Thread
        //implements Runnable
      extends Observable implements Runnable 
{

    // Max size of download buffer.

    private static final int MAX_BUFFER_SIZE = 1024;
    // These are the status names.

    public static final String STATUSES[] = {"Downloading",
            "Paused", "Complete", "Cancelled", "Error"};
    // These are the status codes.

    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 InputStream randIn;
    private RandomAccessFile randOut;
    private URL url;    //download URL

    private long block; //size of this thread

    private long localSize; // number of bytes downloaded

    private int threadId = -1;
    private boolean done = false;
    private int status; // current status of download

    private String currentThreadName;

    /**
   *
   * @param url   File URL
   * @param out   Output file
   * @param block  The block of each thread for downloading
   * @param threadId  Current thread number
   */
    public DownloadThread(URL url, RandomAccessFile out, long block, int threadId) {
        this.url = url;
        this.randOut = out;
        this.block = block;
        this.threadId = threadId;
        this.localSize = -1;
        status = DOWNLOADING;
        
        download();
    }

    /**
     
     @param url  File URL
     @param out  Output file
     @param block The block of each thread for downloading
     @param threadId Current thread number
     @param currentThreadName  This is to mark the temp file name.
     */
    public DownloadThread(URL url, RandomAccessFile out, long block,
            int threadId, String currentThreadName) {
        this.url = url;
       this.randOut = out;
        this.block = block;
        this.threadId = threadId;
        this.localSize = -1;
        this.currentThreadName = currentThreadName;
        status = DOWNLOADING;

        download();
    }

    // Start or resume downloading.
    private void download() {
        Thread thread = new Thread(this);
        thread.start();
       // run();
    }
    public void pause() {
        status = PAUSED;
       stateChanged();
    }

    // Resume this download.

    public void resume() {
       status = DOWNLOADING;
        stateChanged();
        download();
    }

    // Cancel this download.
    public void cancel() {
        status = CANCELLED;
        stateChanged();
    }

    // Mark this download as having an error.
    private void error() {
        status = ERROR;
       stateChanged();
    }
    //start thread

    public void run() {

        String localFile = currentThreadName; //file's path and name

        try {
            // Open connection to URL.
            HttpURLConnection http = (HttpURLConnection) url.openConnection();

            // Specify what portion of file to download.
            http.setRequestProperty("Range", "bytes=" + block * (threadId - 1) + "-");

            randIn = http.getInputStream();

            //downloading
            byte[] buffer = new byte[MAX_BUFFER_SIZE];
            int offset = 0;   // file size reading from server into buffer each time

            System.out.println("Thread " + threadId + " start downloading");

//            bufferedInputStream = new BufferedInputStream(http.getInputStream());
//            fileOutputStream = new FileOutputStream(localFile_tp);
//            dataOutputStream = new DataOutputStream(fileOutputStream);
            System.out.println("锟斤拷锟节斤拷锟斤拷锟侥硷拷 " + localFile + " ...");

            //if downloading
            while ((offset = randIn.read(buffer)) != -1 
                && localSize <= block) {
                // Write buffer to file.
                randOut.write(buffer, 0, offset);
                //dataOutputStream.write(buffer,0,offset);
                localSize += offset;
                stateChanged();
            }
        } catch (Exception e) {
            System.err.println(e);
        } finally {

            // Close file.
            if (randOut != null) {
                try {
                    randOut.close();
                } catch (Exception e) {
                }
            }

            // Close connection to server.
            if (randIn != null) {
                try {
                    randIn.close();
                } catch (Exception e) {
                }
            }
            done = true;
            System.out.println("Thread " + threadId + " end downloading");
        //this.interrupt();
        }
    }

    public boolean isFinished() {
        return done;
    }

    // Notify observers that this download's status has changed.

    private void stateChanged() {
        setChanged();
        notifyObservers();
    }
}