downloadthread.java

用Java开发的多线程下载工具

package download;

/**
 *功能：下载线程类
 */

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

public class DownLoadThread extends Thread
{
	private InputStream in; // 网络下载文件输入流

	private RandomAccessFile out; // 下载文件输出流

	private URL downURL;

	private long block;

	private int threadId = -1;

	private boolean finished = false;

	private boolean err = false;

	private DownLoadInfo downInfo;

	private long startP;

	public DownLoadThread(DownLoadInfo downInfo, int threadId)
	{

		this.block = downInfo.getDownPos()[threadId][1];
		this.threadId = threadId;
		this.downInfo = downInfo;
		startP = downInfo.getDownPos()[threadId][0];
	}

	/**
	 * 功能：获取线程下载是否结束标志 返回值:boolean
	 */
	public boolean isFinished()
	{
		return finished;
	}

	/**
	 * 功能：获取线程下载是否出错标志 返回值:boolean
	 */
	public boolean isError()
	{
		return err;
	}

	public void run()
	{
		HttpURLConnection http;
		try
		{
			downURL = new URL(downInfo.getDownURL());
			http = (HttpURLConnection) downURL.openConnection();
			String sProperty = "bytes=" + startP + "-";
			http.setRequestProperty("Range", sProperty);
			in = http.getInputStream();
			out = new RandomAccessFile(downInfo.getSaveFileName(), "rw");
		}
		catch (IOException e)
		{
			System.err.println("资源文件[" + downInfo.getDownURL() + "]线程"
					+ threadId + "报文申请错误！");
			err = true;
			return;
		}

		byte[] buffer = new byte[1024];
		int offset = 0;
		long localSize = 0;
		long step = 0;
		System.out.println("资源文件[" + downInfo.getDownURL() + "]线程" + threadId
				+ "开始下载");
		try
		{
			out.seek(startP);
			step = (block > 1024) ? 1024 : block;
			while ((offset = in.read(buffer, 0, (int) step)) > 0
					&& localSize <= block)
			{
				if (downInfo.isError())
					break;// 判断其它线程是否出错，如果出错，跳出循环，结束下载线程
				out.write(buffer, 0, offset);
				localSize += offset;
				// 修改文件下载线程进度信息
				{
					downInfo.getDownPos()[threadId][0] = startP + localSize;
					downInfo.getDownPos()[threadId][1] = block - localSize;
				}
				step = block - localSize;
				step = (step > 1024) ? 1024 : step;
				// 更改下载文件长度
				downInfo.setDownLength(offset);
			}
			out.close();
			in.close();
			http.disconnect();
			if (!downInfo.isError())
			{
				finished = true;
				System.out.println("资源文件[" + downInfo.getDownURL() + "]线程"
						+ threadId + "完成下载");
			}
		}
		catch (Exception e)
		{
			System.out.println("资源文件[" + downInfo.getDownURL() + "]线程"
					+ threadId + "下载出错");
			err = true;
			finished = true;
			try
			{
				http.disconnect();
				in.close();
				out.close();
			}
			catch (Exception e1)
			{
			}
		}
	}
}