问题描述

多线程加上断点下载多个文件文件出现问题了

 package cn.com.sinosoft.sfjy.util;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Map;
import java.util.Set;

public class DonwloadUtil {

    public static Map<FileName, DownloadVo> map;

    public DonwloadUtil(Map<FileName, DownloadVo> map) {
        DonwloadUtil.map = map;
        being();
    }

    public void being() {
        System.out.println("++++++++++++++++++++++++++++++++++++++++++++");
        Set<FileName> keySet = map.keySet();
        for (FileName fileName : keySet) {
            map.get(fileName).setFinished(donwload(fileName));
        }
        System.out.println("++++++++++++++++++++++++++++++++++++++++++++");
    }

    public boolean donwload(FileName filename) {
        // 发送get请求，请求这个地址的资源
        try {
            // 构建请求路径
            URL url = new URL(DonwloadUtil.map.get(filename).getDonwloadPath());
            // 发送连接
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            // 请求方式
            conn.setRequestMethod("GET");
            // 请求连接超时
            conn.setConnectTimeout(5000);
            // 连接中超时
            conn.setReadTimeout(5000);
            // 请求连接成功 200
            if (conn.getResponseCode() == 200) {
                // 拿到所请求资源文件的长度
                long length = conn.getContentLength();

                File file = new File(DonwloadUtil.map.get(filename).getTargetPath() + "/"
                        + DonwloadUtil.map.get(filename).getFileName());
                // 生成临时文件
                RandomAccessFile raf = new RandomAccessFile(file, "rwd");
                // 设置临时文件的大小
                raf.setLength(length);
                raf.close();
                // 计算出每个线程应该下载多少字节
                long size = length / DonwloadUtil.map.get(filename).getThreadCount();

                for (int i = 0; i < DonwloadUtil.map.get(filename).getThreadCount(); i++) {
                    // 计算线程下载的开始位置和结束位置
                    long startIndex = i * size;
                    long endIndex = (i + 1) * size - 1;
                    // 如果是最后一个线程，那么结束位置写死
                    if (i == DonwloadUtil.map.get(filename).getThreadCount() - 1) {
                        endIndex = length - 1;
                    }
                    System.out.println(filename+"线程" + i + "的下载区间是：" + startIndex + "---" + endIndex);
                    new DownLoadThread(startIndex, endIndex, i, filename).start();

                }
            }
            return true;
        } catch (Exception e) {
            e.printStackTrace();
            return false;
        }
    }

}

class DownLoadThread extends Thread {
    long startIndex;
    long endIndex;
    int threadId;
    FileName filename;

    public DownLoadThread(long startIndex, long endIndex, int threadId, FileName filename) {
        super();
        this.startIndex = startIndex;
        this.endIndex = endIndex;
        this.threadId = threadId;
        this.filename = filename;
    }

    @Override
    public  void run() {
        try {
            // 存放当前线程的下载进度文件
            File progressFile = new File(filename+""+threadId + ".txt");
            // 判断进度临时文件是否存在
            if (progressFile.exists()) {
                FileInputStream fis = new FileInputStream(progressFile);
                BufferedReader br = new BufferedReader(new InputStreamReader(fis));
                // 从进度临时文件中读取出上一次下载的总进度，然后与原本的开始位置相加，得到新的开始位置
                startIndex += Integer.parseInt(br.readLine());
                fis.close();
            }
            // System.out.println("线程" + threadId + "的下载区间是：" + startIndex +
            // "---" + endIndex);
            // 再次发送http请求，下载原文件
            HttpURLConnection conn;
            URL url = new URL(DonwloadUtil.map.get(filename).getDonwloadPath());
            // 发送连接
            conn = (HttpURLConnection) url.openConnection();
            // 请求方式
            conn.setRequestMethod("GET");
            // 请求连接超时
            conn.setConnectTimeout(5000);
            // 连接中超时
            conn.setReadTimeout(5000);
            // 设置本次http请求所请求的数据的区间
            conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex);
            //System.out.println(filenaem+conn.getResponseCode());
            // 请求部分数据，相应码是206
            if (conn.getResponseCode() == 206) {
                // 流里此时只有1/3原文件的数据
                InputStream is = conn.getInputStream();
                byte[] b = new byte[1024];
                int len = 0;
                int total = 0;
                // 拿到临时文件的输出流
                File file = new File(DonwloadUtil.map.get(filename).getTargetPath() + "/"
                        + DonwloadUtil.map.get(filename).getFileName());
                // 生成临时文件
                RandomAccessFile raf = new RandomAccessFile(file, "rwd");
                // 把文件的写入位置移动至startIndex
                raf.seek(startIndex);
                while ((len = is.read(b)) != -1) {
                    // 每次读取流里数据之后，同步把数据写入临时文件
                    raf.write(b, 0, len);
                    total += len;
                    System.out.println(filename+"线程" + threadId + "下载了" + total);

                    // 生成一个专门用来记录下载进度的临时文件
                    RandomAccessFile progressRaf = new RandomAccessFile(progressFile, "rwd");
                    // 每次读取流里数据之后，同步把当前线程下载的总进度写入进度临时文件中
                    progressRaf.write((total + "").getBytes());
                    progressRaf.close();
                }
                System.out.println(filename+"线程" + threadId + "下载完毕！");
                raf.close();

                DonwloadUtil.map.get(filename)
                        .setFinishedThread(DonwloadUtil.map.get(filename).getFinishedThread() + 1);
                synchronized (DonwloadUtil.map.get(filename).getDonwloadPath()) {
                    if (DonwloadUtil.map.get(filename).getFinishedThread() == DonwloadUtil.map.get(filename)
                            .getThreadCount()) {
                        for (int i = 0; i < DonwloadUtil.map.get(filename).getThreadCount(); i++) {
                            File f = new File(filename+""+i+ ".txt");
                            f.delete();
                        }
                        DonwloadUtil.map.get(filename).setFinishedThread(0);
                    }
                }

            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

解决方案

http://www.cnblogs.com/hoojo/archive/2011/09/30/2196767.html

解决方案二：

多线程断点下载文件
Android多线程断点下载文件
Android多线程实现文件断点下载