--> 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,如果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) { //如果小于4M connectCount = 1; } else if (size < 10 * 1024 * 1024) { //如果文件小于10M 则两个连接 connectCount = 2; } else if (size < 30 * 1024 * 1024) { //如果文件小于80M 则使用6个连接 connectCount = 3; } else if (size < 60 * 1024 * 1024) { //如果小于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<Object>() { @Override public Object run() { try { Method getCleanerMethod = mappedByteBuffer.getClass().getMethod("cleaner", new Class[0]); getCleanerMethod.setAccessible(true); sun.misc.Cleaner cleaner = (sun.misc.Cleaner) getCleanerMethod.invoke(mappedByteBuffer, new Object[0]); cleaner.clean(); } catch (Exception e) { //LOG.error("unmapFileChannel." + e.getMessage()); } return null; } }); } catch (Exception e) { log.debug("异常->exception=true"); exception = true; log.error(e); } } private void timer() { Timer timer = new Timer(); //延迟3秒,3秒运行一次 timer.schedule(new TimerTask() { @Override public void run() { log.debug(String.format("已下载-->%s -> %s",(((double) downloaded) / size * 100) + "%", url)); //如果上一次的下载大小与当前的一样就退出 if(prevDownloaded.get() ==downloaded && downloaded<size){ if(loseNum.getAndIncrement()>=10){ log.debug(String.format("上次下载%s与当前下载%s一致,exception->true url:%s ",prevDownloaded.get(),downloaded,url)); exception = true; } } //如果下载完成或者异常就退出 if(downloaded>=size || exception){ stop = true; cancel(); } //设置上次下载的大小等于现在的大小 prevDownloaded.set(downloaded); } },3000,3000); } public void start() throws IOException { if (exists) { log.info("文件已存在." + this.url); Thread.currentThread().interrupt(); return; } while (Thread.activeCount()>maxThread){ try { Thread.sleep(1000); } catch (InterruptedException e) {} } init(); timer(); CountDownLatch countDownLatch = new CountDownLatch(connections.length); log.debug("开始下载:" + url); for (int i = 0; i < connections.length; i++) { new DownloadPart(countDownLatch, i).start(); } end(countDownLatch); } private boolean rename(File tempFile){ File file = new File(this.savePath); boolean isRename=tempFile.renameTo(file); if(!isRename){ try { IOUtils.copy(new FileInputStream(tempFile),new FileOutputStream(file)); } catch (IOException e) { log.error(e); } } return true; } public void end(CountDownLatch countDownLatch){ try { //超过指定时间就直接结束 countDownLatch.await(timeout, TimeUnit.MILLISECONDS); } catch (InterruptedException e) { exception = true; log.error(e); log.info("下载失败:"+this.url); } finally { try { channel.force(true); channel.close(); randomAccessFile.close(); } catch (IOException e) { log.error(e); } File temp = new File(this.savePath+".temp"); log.debug(String.format("%s %s", exception, this.url)); //如果有异常则删除已下载的临时文件 if(exception){ if(!temp.delete()){ if(temp!=null)temp.delete(); } }else{ try { Thread.sleep(100); } catch (InterruptedException e) {} rename(temp); setChanged(); notifyObservers(this.url); log.info("下载成功:"+this.url); } } } private class Connection { long start, end; public Connection(long start, long end) { this.start = start; this.end = end; } public InputStream getInputStream() throws IOException { return method(start, end).getResponseBodyAsStream(); } } private class DownloadPart implements Runnable { CountDownLatch countDownLatch; int i; public DownloadPart(CountDownLatch countDownLatch, int i) { this.countDownLatch = countDownLatch; this.i = i; } public void start() { new Thread(this).start(); } @Override public void run() { MappedByteBuffer buffer = null; InputStream is = null; try { is = connections[i].getInputStream(); buffer = channel.map(FileChannel.MapMode.READ_WRITE, connections[i].start, connections[i].end - connections[i].start); byte[] bytes = new byte[4 * 1024]; int len; while ((len = is.read(bytes)) != -1 && !exception && !stop) { buffer.put(bytes, 0, len); downloaded+= len; } log.debug(String.format("file block had downloaded.%s %s",i,url)); } catch (IOException e) { log.error(e); } finally { unmapFileChannel(buffer); if(buffer != null)buffer.clear(); if (is != null) try { is.close(); } catch (IOException e) { } countDownLatch.countDown(); } } } }