Java Nio 多线程网络下载

--> 默认最多50个线程 同一文件下载失败延迟超过30秒就结束下载

--> 下载5分钟超时时间，假设5分钟内未下载完就结束下载

--> 依赖 commons-httpclient 与 commons-io 包

package com.leunpha;

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.methods.GetMethod;
import org.apache.commons.httpclient.params.HttpClientParams;
import org.apache.commons.io.IOUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import java.io.*;
import java.lang.reflect.Method;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.Observable;
import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import java.util.zip.ZipFile;

/**
 * User: zhoujingjie
 * Date: 14-4-18
 * Time: 下午12:52
 */
public class Downloader extends Observable {
    protected String url, savePath;             //下载地址与保存路径
    protected FileChannel channel;              //保存文件的通道
    protected long size, perSize;              //文件大小与每一个小文件的大小
    protected volatile long downloaded;       // 已下载的
    protected int connectCount;                 //连接数
    protected Connection[] connections;         //连接对象
    protected boolean isSupportRange;         //是否支持断点下载
    protected long timeout;                     //超时
    protected boolean exists;                   //是否存在
    private RandomAccessFile randomAccessFile;
    protected volatile boolean stop;            //停止
    private static volatile  boolean exception; //是否异常
    private AtomicLong prevDownloaded = new AtomicLong(0); //上一次的下载结果
    private static Log log = LogFactory.getLog(Downloader.class);
    private AtomicInteger loseNum = new AtomicInteger(0);
    private int maxThread;

    public Downloader(String url, String savePath) throws IOException {
        //超时一小时
        this(url, savePath, 1000 * 60*5,50);
    }

    public Downloader(String url, String savePath, long timeout,int maxThread) throws FileNotFoundException {
        this.timeout = timeout;
        this.url = url;
        this.maxThread = maxThread;
        File file = new File(savePath);
        if (!file.exists()) file.mkdirs();
        this.savePath= file.getAbsolutePath() + "/" + url.substring(url.lastIndexOf("/"));
        exists = new File(this.savePath).exists();
        if(!exists){
            randomAccessFile=   new RandomAccessFile(this.savePath+".temp", "rw");
            channel =randomAccessFile.getChannel();
        }
    }


    public GetMethod method(long start, long end) throws IOException {
        GetMethod method = new GetMethod(Downloader.this.url);
        method.setRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 6.2; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/30.0.1599.101 Safari/537.36");
        if (end > 0) {
            method.setRequestHeader("Range", "bytes=" + start + "-" + (end - 1));
        } else {
            method.setRequestHeader("Range", "bytes=" + start + "-");
        }
        HttpClientParams clientParams = new HttpClientParams();
        //5秒超时
        clientParams.setConnectionManagerTimeout(5000);
        HttpClient client = new HttpClient(clientParams);
        client.executeMethod(method);
        int statusCode = method.getStatusCode();
        if (statusCode >= 200 && statusCode < 300) {
            isSupportRange = (statusCode == 206) ? true : false;
        }
        return method;
    }

    public void init() throws IOException {
        size = method(0, -1).getResponseContentLength();
        if (isSupportRange) {
            if (size < 4 * 1024 * 1024) {  //假设小于4M
                connectCount = 1;
            } else if (size < 10 * 1024 * 1024) { //假设文件小于10M 则两个连接
                connectCount = 2;
            } else if (size < 30 * 1024 * 1024) { //假设文件小于80M 则使用6个连接
                connectCount = 3;
            } else if (size < 60 * 1024 * 1024) {          //假设小于60M 则使用10个连接
                connectCount = 4;
            } else {
                //否则为10个连接
                connectCount = 5;
            }
        } else {
            connectCount = 1;
        }
        log.debug(String.format("%s size:%s connectCount:%s", this.url, this.size, this.connectCount));
        perSize = size / connectCount;
        connections = new Connection[connectCount];
        long offset = 0;
        for (int i = 0; i < connectCount - 1; i++) {
            connections[i] = new Connection(offset, offset + perSize);
            offset += perSize;
        }
        connections[connectCount - 1] = new Connection(offset, size);
    }


    /**
     * 强制释放内存映射
     *
     * @param mappedByteBuffer
     */
    static void unmapFileChannel(final MappedByteBuffer mappedByteBuffer) {
        try {
            if (mappedByteBuffer == null) {
                return;
            }
            mappedByteBuffer.force();
            AccessController.doPrivileged(new PrivilegedAction