Java实现多线程下载、断点续传

先看下以前做的一个小项目，多线程下载器。

http://blog.csdn.net/maoxiang/archive/2008/05/24/2478707.aspx

 

 

这几天，重新整理了一下，写了一个工具类，方便在各种场合下使用。

 

设计的几个要点:

 

1. 把每个下载文件切成若干个块(Block)，然后得到一个位图，用来标记每个块的下载情况，并保存到文件里，用于实现断点续传。

2. HTTP Header里增加Range，如果服务器返回Cotent-Range 说明服务器支持文件定位，可以实现多线程下载。

 

接下来直接看看代码吧：

/** * 专注互联网,分享创造价值 * [e-mail] * 2010-3-30下午04:40:06 */package common.http;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.InetSocketAddress;import java.net.Proxy;import java.net.SocketAddress;import java.net.URL;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.concurrent.atomic.AtomicLong;import org.apache.commons.codec.binary.Base64;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;/** * 一个多线程支持断点续传的工具类<br/> * 2010-03 用Htpp Component重写 */public class HttpDownloader {private final Log log = LogFactory.getLog(getClass().getName());private int threads = 5; // 总共的线程数private int maxThreads = 10; // 最大的线程数private String destUrl; // 目标的URLprivate String savePath; // 保存的路径private File lockFile;// 用来保存进度的文件private String userAgent = "jHttpDownload";private boolean useProxy = false;private String proxyServer;private int proxyPort;private String proxyUser;private String proxyPassword;private int blockSize = 1024 * 4; // 4K 一个块// 1个位代表一个块,，用来标记是否下载完成private byte[] blockSet;private int blockPage; // 每个线程负责的大小private int blocks;private boolean running; // 是否运行中,避免线程不能释放// =======下载进度信息private long beginTime;private AtomicLong downloaded = new AtomicLong(0); // 已下载的字节数/private long fileLength; // 总的字节数// 监控线程,用来保存进度和汇报进度private MonitorThread monitorThread = new MonitorThread();public HttpDownloader(String destUrl, String savePath, int threads) {this.threads = threads;this.destUrl = destUrl;this.savePath = savePath;}public HttpDownloader(String destUrl, String savePath) {this(destUrl, savePath, 5);}/** * 开始下载 */public boolean download() {log.info("下载文件" + destUrl + ",保存路径=" + savePath);beginTime = System.currentTimeMillis();boolean ok = false;try {File saveFile = new File(savePath);lockFile = new File(savePath + ".lck");if (lockFile.exists() && !lockFile.canWrite()) {throw new Exception("文件被锁住，或许已经在下载中了");}File parent = saveFile.getParentFile();if (!parent.exists()) {log.info("创建目录=" + parent.getAbsolutePath());}if (!parent.canWrite()) {throw new Exception("保存目录不可写");}if (saveFile.exists()) {if (!saveFile.canWrite()) {throw new Exception("保存文件不可写,无法继续下载");}log.info("检查之前下载的文件");if (lockFile.exists()) {log.info("加载之前下载进度");loadPrevious();}} else {lockFile.createNewFile();}// 1初始化httpClientHttpURLConnection httpUrlConnection = getHttpConnection(0);String contentLength = httpUrlConnection.getHeaderField("Content-Length");if (contentLength != null) {try {fileLength = Long.parseLong(contentLength);} catch (Exception e) {}}log.info("下载文件的大小:" + fileLength);if (fileLength <= 0) {// 不支持多线程下载,采用单线程下载log.info("服务器不能返回文件大小，采用单线程下载");threads = 1;}if (httpUrlConnection.getHeaderField("Content-Range") == null) {log.info("服务器不支持断点续传");threads = 1;} else {log.info("服务器支持断点续传");}//if (fileLength > 0 && parent.getFreeSpace() < fileLength) {throw new Exception("磁盘空间不够");}if (fileLength > 0) {int i = (int) (fileLength / blockSize);if (fileLength % blockSize > 0) {i++;}blocks = i;} else {// 一个块 blocks = 1;}if (blockSet != null) {log.info("检查文件，是否能够续传");if (blockSet.length != fileLength / (8l * blockSize)) {log.info("文件大小已改变，需要重新下载");blockSet = null;}}if (blockSet == null) {blockSet = BitUtil.createBit(blocks);}log.info("文件的块数:" + blocks + "," + blockSet.length);if (threads > maxThreads) {log.info("超过最大线程数，使用最大线程数");threads = maxThreads;}blockPage = blocks / threads; // 每个线程负责的块数log.info("分配线程。线程数量=" + threads + ",块总数=" + blocks + ",总字节数="+ fileLength + ",每块大小=" + blockSize + ",块/线程=" + blockPage);// 检查running = true;// 创建一个线程组,方便观察和调试ThreadGroup downloadGroup = new ThreadGroup("download");for (int i = 0; i < threads; i++) {int begin = i * blockPage;int end = (i + 1) * blockPage;if (i == threads - 1 && blocks % threads > 0) {// 如果最后一个线程，有余数，需要修正end = blocks;}// 扫描每个线程的块是否有需要下载的boolean needDownload = false;for (int j = begin; j < end; j++) {if (!BitUtil.getBit(blockSet, j)) {needDownload = true;break;}}if (!needDownload) {log.info("所有块已经下载完毕.Begin=" + begin + ",End=" + end);}// 启动下载其他线程DownloadThread downloadThread = new DownloadThread(downloadGroup, i, begin, end);downloadThread.start();}monitorThread.setStop(false);monitorThread.start();// 也可以用Thread.join 实现等待进程完成while (downloadGroup.activeCount() > 0) {Thread.sleep(2000);}ok = true;} catch (Exception e) {e.printStackTrace();log.error(e);} finally {// closeHttpClient();}if (ok) {log.info("删除进度文件:" + lockFile.getAbsolutePath());lockFile.delete();}monitorThread.setStop(true);log.info("下载完成，耗时:"+ getTime((System.currentTimeMillis() - beginTime) / 1000));return ok;}private void loadPrevious() throws Exception {ByteArrayOutputStream outStream = new ByteArrayOutputStream();FileInputStream inStream = new FileInputStream(lockFile);byte[] buffer = new byte[4096];int n = 0;while (-1 != (n = inStream.read(buffer))) {outStream.write(buffer, 0, n);}outStream.close();inStream.close();blockSet = outStream.toByteArray();log.info("之前的文件大小应该是:" + blockSet.length * 8l * blockSize + ",一共有:"+ blockSet.length + "块");}private HttpURLConnection httpConnection0; // 用来快速返回,减少一次连接private HttpURLConnection getHttpConnection(long pos) throws IOException {if (pos == 0 && httpConnection0 != null) {return httpConnection0;}URL url = new URL(destUrl);log.debug("开始一个Http请求连接。Url=" + url + "定位:" + pos + "/n");// 默认的会处理302请求HttpURLConnection.setFollowRedirects(false);HttpURLConnection httpConnection = null;if (useProxy) {log.debug("使用代理进行连接.ProxyServer=" + proxyServer + ",ProxyPort="+ proxyPort);SocketAddress addr = new InetSocketAddress(proxyServer, proxyPort);Proxy proxy = new Proxy(Proxy.Type.HTTP, addr);httpConnection = (HttpURLConnection) url.openConnection(proxy);if (proxyUser != null && proxyPassword != null) {String encoded = new String(Base64.encodeBase64(new String(proxyUser + ":" + proxyPassword).getBytes()));httpConnection.setRequestProperty("Proxy-Authorization","Basic " + encoded);}} else {httpConnection = (HttpURLConnection) url.openConnection();}httpConnection.setRequestProperty("User-Agent", userAgent);httpConnection.setRequestProperty("RANGE", "bytes=" + pos + "-");int responseCode = httpConnection.getResponseCode();log.debug("服务器返回:" + responseCode);Map<String, List<String>> headers = httpConnection.getHeaderFields();Iterator<String> iterator = headers.keySet().iterator();while (iterator.hasNext()) {String key = iterator.next();String value = "";for (String v : headers.get(key)) {value = ";" + v;}log.debug(key + "=" + value);}if (responseCode < 200 || responseCode >= 400) {throw new IOException("服务器返回无效信息:" + responseCode);}if (pos == 0) {httpConnection0 = httpConnection;}return httpConnection;}public void returnConnection(HttpURLConnection connecton) {if (connecton != null)connecton.disconnect();connecton = null;}private String getDesc() {long downloadBytes = downloaded.longValue();return String.format("已下载/总大小=%s/%s(%s),速度:%s,耗时:%s,剩余大小:%d",getFileSize(downloadBytes),getFileSize(fileLength),getProgress(fileLength, downloadBytes),getFileSize(downloadBytes/ ((System.currentTimeMillis() - beginTime) / 1000 + 1)),getTime((System.currentTimeMillis() - beginTime) / 1000),fileLength - downloadBytes);}private String getFileSize(long totals) {// 计算文件大小int i = 0;String j = "BKMGT";float s = totals;while (s > 1024) {s /= 1024;i++;}return String.format("%.2f", s) + j.charAt(i);}private String getProgress(long totals, long read) {if (totals == 0)return "0%";return String.format("%d", read * 100 / totals) + "%";}private String getTime(long seconds) {int i = 0;String j = "秒分时天";long s = seconds;String result = "";while (s > 0) {if (s % 60 > 0) {result = String.valueOf(s % 60) + (char) j.charAt(i) + result;}s /= 60;i++;}return result;}/** * 一个下载线程. */private class DownloadThread extends Thread {private RandomAccessFile destFile; // 用来实现保存的随机文件private int id = 0;private int blockBegin = 0; // 开始块private int blockEnd = 0; // 结束块private long pos;// 绝对指针private String getThreadName() {return "DownloadThread-" + id + "=>";}public DownloadThread(ThreadGroup group, int id, int blockBegin,int blockEnd) throws Exception {super(group, "downloadThread-" + id);this.id = id;this.blockBegin = blockBegin;this.blockEnd = blockEnd;this.pos = 1l * blockBegin * blockSize; // 转换为长整型destFile = new RandomAccessFile(savePath, "rw");}public void run() {BufferedInputStream inputStream = null;try {log.info(getThreadName() + "下载线程." + this.toString());log.info(getThreadName() + ":定位文件位置.Pos=" + 1l * blockBegin* blockSize);destFile.seek(1l * blockBegin * blockSize);log.info(getThreadName() + ":开始下载.[ " + blockBegin + " - "+ blockEnd + "]");HttpURLConnection httpConnection = getHttpConnection(pos);inputStream = new BufferedInputStream(httpConnection.getInputStream());byte[] b = new byte[blockSize];while (blockBegin < blockEnd) {if (!running) {log.info(getThreadName() + ":停止下载.当前块:" + blockBegin);return;}log.debug(getThreadName() + "下载块=" + blockBegin);int counts = 0; // 已下载字节数if (BitUtil.getBit(blockSet, blockBegin)) {log.debug(getThreadName() + ":块下载已经完成=" + blockBegin);destFile.skipBytes(blockSize);int skips = 0;while (skips < blockSize) {skips += inputStream.skip(blockSize - skips);}downloaded.addAndGet(blockSize);} else {while (counts < blockSize) {int read = inputStream.read(b, 0, blockSize- counts);if (read < 0)break;counts += read;destFile.write(b, 0, read);downloaded.addAndGet(read);}BitUtil.setBit(blockSet, blockBegin, true); // 标记已经下载完成}blockBegin++;}httpConnection.disconnect();log.info(getThreadName() + "下载完成.");return;} catch (Exception e) {log.error(getThreadName() + "下载错误:" + e.getMessage());e.printStackTrace();} finally {try {if (inputStream != null)inputStream.close();} catch (Exception te) {log.error(te);}try {if (destFile != null)destFile.close();} catch (Exception te) {log.error(te);}}}}// 监控线程,并保存进度，方便下次断点续传private class MonitorThread extends Thread {boolean stop = false;public void setStop(boolean stop) {this.stop = stop;}public void run() {FileOutputStream saveStream = null;try {while (running && !stop) {saveStream = new FileOutputStream(lockFile);log.info(getDesc());// 保存进度saveStream.write(blockSet, 0, blockSet.length);sleep(1000);saveStream.close();}} catch (Exception e) {e.printStackTrace();log.error(e);} finally {}}}// 用来操作位的工具private static class BitUtil {public static byte[] createBit(int len) {int size = len / Byte.SIZE;if (len % Byte.SIZE > 0) {size++;}return new byte[size];}/** 取出某位，是0 还是1 */public static boolean getBit(byte[] bits, int pos) {int i = pos / Byte.SIZE;int b = bits[i];int j = pos % Byte.SIZE;byte c = (byte) (0x80 >>> (j - 1));return b == c;}/** 设置某位，是0 还是1 */public static void setBit(byte[] bits, int pos, boolean flag) {int i = pos / Byte.SIZE;byte b = bits[i];int j = pos % Byte.SIZE;byte c = (byte) (0x80 >>> (j - 1));if (flag) {bits[i] = (byte) (b | c);} else {c = (byte) (0xFF ^ c);bits[i] = (byte) (b & c);}}}}

 

我写了一个用Http Component组件实现的，不过目前版本，4.0.1 在连接池管理上貌似有问题，连接不能正确关闭，有兴趣的可以调试看看

 

/** * 专注互联网,分享创造价值 * [e-mail] * 2010-3-30下午04:40:06 */package common.http;import java.io.BufferedInputStream;import java.io.ByteArrayOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.RandomAccessFile;import java.util.concurrent.atomic.AtomicLong;import javax.net.ssl.SSLHandshakeException;import org.apache.commons.logging.Log;import org.apache.commons.logging.LogFactory;import org.apache.http.Header;import org.apache.http.HttpEntityEnclosingRequest;import org.apache.http.HttpHost;import org.apache.http.HttpRequest;import org.apache.http.HttpResponse;import org.apache.http.NoHttpResponseException;import org.apache.http.auth.AuthScope;import org.apache.http.auth.UsernamePasswordCredentials;import org.apache.http.client.HttpRequestRetryHandler;import org.apache.http.client.methods.HttpGet;import org.apache.http.conn.ClientConnectionManager;import org.apache.http.conn.params.ConnManagerParams;import org.apache.http.conn.params.ConnPerRoute;import org.apache.http.conn.params.ConnRoutePNames;import org.apache.http.conn.routing.HttpRoute;import org.apache.http.conn.scheme.PlainSocketFactory;import org.apache.http.conn.scheme.Scheme;import org.apache.http.conn.scheme.SchemeRegistry;import org.apache.http.impl.client.DefaultHttpClient;import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager;import org.apache.http.params.BasicHttpParams;import org.apache.http.params.CoreProtocolPNames;import org.apache.http.params.HttpParams;import org.apache.http.protocol.BasicHttpContext;import org.apache.http.protocol.ExecutionContext;import org.apache.http.protocol.HttpContext;/** * 一个多线程支持断点续传的工具类<br/> * 2010-03 用Htpp Component重写 */public class HttpDownloader1 {private final Log log = LogFactory.getLog(getClass().getName());private int threads = 5; // 总共的线程数private int maxThreads = 10; // 最大的线程数private String destUrl; // 目标的URLprivate String savePath; // 保存的路径private File lockFile;// 用来保存进度的文件private String userAgent = "jHttpDownload";private boolean useProxy = false;private String proxyServer;private int proxyPort;private String proxyUser;private String proxyPassword;private int blockSize = 1024 * 4; // 4K 一个块// 1个位代表一个块,，用来标记是否下载完成private byte[] blockSet;private int blockPage; // 每个线程负责的大小private int blocks;private boolean running; // 是否运行中,避免线程不能释放private DefaultHttpClient httpClient;//// =======下载进度信息private long beginTime;private AtomicLong downloaded = new AtomicLong(0); // 已下载的字节数/private long fileLength; // 总的字节数// 监控线程,用来保存进度和汇报进度private MonitorThread monitorThread = new MonitorThread();public HttpDownloader1(String destUrl, String savePath, int threads) {this.threads = threads;this.destUrl = destUrl;this.savePath = savePath;}public HttpDownloader1(String destUrl, String savePath) {this(destUrl, savePath, 5);}/** * 开始下载 */public boolean download() {log.info("下载文件" + destUrl + ",保存路径=" + savePath);beginTime = System.currentTimeMillis();boolean ok = false;try {File saveFile = new File(savePath);lockFile = new File(savePath + ".lck");if (lockFile.exists() && !lockFile.canWrite()) {throw new Exception("文件被锁住，或许已经在下载中了");}File parent = saveFile.getParentFile();if (!parent.exists()) {log.info("创建目录=" + parent.getAbsolutePath());}if (!parent.canWrite()) {throw new Exception("保存目录不可写");}if (saveFile.exists()) {if (!saveFile.canWrite()) {throw new Exception("保存文件不可写,无法继续下载");}log.info("检查之前下载的文件");if (lockFile.exists()) {log.info("加载之前下载进度");loadPrevious();}} else {lockFile.createNewFile();}// 1初始化httpClientsetupHttpClient();HttpResponse response = getResponse(0);Header length = response.getFirstHeader("Content-Length");if (length != null) {try {fileLength = Long.parseLong(length.getValue());} catch (Exception e) {}}log.info("下载文件的大小:" + fileLength);if (fileLength <= 0) {// 不支持多线程下载,采用单线程下载log.info("服务器不能返回文件大小，采用单线程下载");threads = 1;}if (response.getFirstHeader("Content-Range") == null) {log.info("服务器不支持断线续传");threads = 1;} else {log.info("服务器支持断点续传");}if (blockSet != null) {log.info("检查文件，是否能够续传");if (blockSet.length * 8l * blockSize < fileLength) {log.info("文件大小已改变，需要重新下载");blockSet = null;}}//if (fileLength > 0 && parent.getFreeSpace() < fileLength) {throw new Exception("磁盘空间不够");}if (fileLength > 0) {int i = (int) (fileLength / blockSize);if (fileLength % blockSize > 0) {i++;}blocks = i;log.info("文件的块数:" + blocks);blockSet = BitUtil.createBit(blocks);} else {// 一个块blocks = 1;}blockPage = blocks / threads; // 每个线程负责的块数log.info("分配线程。线程数量=" + threads + ",块总数=" + blocks + ",总字节数="+ fileLength + ",每块大小=" + blockSize + ",块/线程=" + blockPage);// 检查running = true;ThreadGroup downloadGroup = new ThreadGroup("download");for (int i = 0; i < threads; i++) {int begin = i * blockPage;int end = (i + 1) * blockPage;if (i == threads - 1 && blocks % threads > 0) {// 如果最后一个线程，有余数，需要修正end = blocks;}// 扫描每个线程的块是否有需要下载的boolean needDownload = false;for (int j = begin; j < end; j++) {if (!BitUtil.getBit(blockSet, j)) {needDownload = true;break;}}if (!needDownload) {log.info("所有块已经下载完毕.Begin=" + begin + ",End=" + end);}// 启动下载其他线程DownloadThread downloadThread = new DownloadThread(downloadGroup, i, begin, end);downloadThread.start();}monitorThread.setStop(false);monitorThread.start();while (downloadGroup.activeCount() > 0) {Thread.sleep(2000);}ok = true;} catch (Exception e) {e.printStackTrace();log.error(e);} finally {// closeHttpClient();if (ok) {log.info("删除进度文件:" + lockFile.getAbsolutePath());lockFile.delete();}httpClient = null;}monitorThread.setStop(true);log.info("下载完成，耗时:"+ getTime((System.currentTimeMillis() - beginTime) / 1000));return ok;}private void loadPrevious() throws Exception {ByteArrayOutputStream outStream = new ByteArrayOutputStream();FileInputStream inStream = new FileInputStream(lockFile);byte[] buffer = new byte[4096];int n = 0;while (-1 != (n = inStream.read(buffer))) {outStream.write(buffer, 0, n);}outStream.close();inStream.close();blockSet = outStream.toByteArray();log.debug("之前的文件大小应该是:" + blockSet.length * 8l * blockSize);}private void setupHttpClient() throws Exception {HttpParams params = new BasicHttpParams();SchemeRegistry schemeRegistry = new SchemeRegistry();schemeRegistry.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80));ClientConnectionManager cm = new ThreadSafeClientConnManager(params,schemeRegistry);httpClient = new DefaultHttpClient(cm, params);httpClient.getParams().setParameter(CoreProtocolPNames.USER_AGENT,userAgent);ConnPerRoute defaultConnPerRoute = new ConnPerRoute() {public int getMaxForRoute(HttpRoute route) {return maxThreads;}};httpClient.getParams().setParameter(ConnManagerParams.MAX_CONNECTIONS_PER_ROUTE,defaultConnPerRoute);// 设置重试机制httpClient.setHttpRequestRetryHandler(myRetryHandler);if (useProxy) {log.info("采用代理服务器=" + proxyServer + ",端口=" + proxyPort);final HttpHost proxy = new HttpHost(proxyServer, proxyPort, "http");httpClient.getParams().setParameter(ConnRoutePNames.DEFAULT_PROXY,proxy);if (proxyUser != null && proxyPassword != null) {httpClient.getCredentialsProvider().setCredentials(AuthScope.ANY,new UsernamePasswordCredentials(proxyUser,proxyPassword));}}}private HttpResponse response0; // 用来快速返回,减少一次连接private HttpResponse getResponse(long pos) throws Exception {if (pos == 0 && response0 != null) {return response0;}HttpGet httpget = new HttpGet(destUrl);HttpContext localContext = new BasicHttpContext();// 实现多线程下载的核心，也可以用来实现断点续传httpget.addHeader("RANGE", "bytes=" + pos + "-");HttpResponse response = httpClient.execute(httpget, localContext);if (pos == 0) {response0 = response;}return response;}// 重试机制private HttpRequestRetryHandler myRetryHandler = new HttpRequestRetryHandler() {public boolean retryRequest(IOException exception, int executionCount,HttpContext context) {if (executionCount >= 5) {return false;}if (exception instanceof NoHttpResponseException) {return true;}if (exception instanceof SSLHandshakeException) {return false;}HttpRequest request = (HttpRequest) context.getAttribute(ExecutionContext.HTTP_REQUEST);boolean idempotent = !(request instanceof HttpEntityEnclosingRequest);if (idempotent) {return true;}return false;}};private String getDesc() {long downloadBytes = downloaded.longValue();return String.format("已下载/总大小=%s/%s(%s),速度:%s,耗时:%s,剩余大小:%d",getFileSize(downloadBytes), getFileSize(fileLength),getProgress(fileLength, downloadBytes),getFileSize(downloadBytes/ ((System.currentTimeMillis() - beginTime) / 1000)),getTime((System.currentTimeMillis() - beginTime) / 1000),fileLength - downloadBytes);}private String getFileSize(long totals) {// 计算文件大小int i = 0;String j = "BKMGT";float s = totals;while (s > 1024) {s /= 1024;i++;}return String.format("%.2f", s) + j.charAt(i);}private String getProgress(long totals, long read) {if (totals == 0)return "0%";return String.format("%d", read * 100 / totals) + "%";}private String getTime(long seconds) {int i = 0;String j = "秒分时天";long s = seconds;String result = "";while (s > 0) {if (s % 60 > 0) {result = String.valueOf(s % 60) + (char) j.charAt(i) + result;}s /= 60;i++;}return result;}/** * 一个下载线程. */private class DownloadThread extends Thread {private RandomAccessFile destFile; // 用来实现保存的随机文件private int id = 0;private int blockBegin = 0; // 开始块private int blockEnd = 0; // 结束块private long pos;// 绝对指针private String getThreadName() {return "DownloadThread-" + id + "=>";}public DownloadThread(ThreadGroup group, int id, int blockBegin,int blockEnd) throws Exception {super(group, "downloadThread-" + id);this.id = id;this.blockBegin = blockBegin;this.blockEnd = blockEnd;this.pos = 1l * blockBegin * blockSize; // 转换为长整型destFile = new RandomAccessFile(savePath, "rw");}public void run() {BufferedInputStream inputStream = null;try {log.info(getThreadName() + "下载线程." + this.toString());log.info(getThreadName() + ":定位文件位置.Pos=" + 1l * blockBegin* blockSize);destFile.seek(1l * blockBegin * blockSize);log.info(getThreadName() + ":开始下载.[ " + blockBegin + " - "+ blockEnd + "]");HttpResponse response = getResponse(pos);inputStream = new BufferedInputStream(response.getEntity().getContent());byte[] b = new byte[blockSize];while (blockBegin < blockEnd) {if (!running) {log.info(getThreadName() + ":停止下载.当前块:" + blockBegin);return;}log.debug(getThreadName() + "下载块=" + blockBegin);int counts = 0; // 已下载字节数if (BitUtil.getBit(blockSet, blockBegin)) {log.debug(getThreadName() + ":块下载已经完成=" + blockBegin);destFile.skipBytes(blockSize);int skips = 0;while (skips < blockSize) {skips += inputStream.skip(blockSize - skips);}downloaded.addAndGet(blockSize);} else {while (counts < blockSize) {int read = inputStream.read(b, 0, blockSize- counts);if (read < 0)break;counts += read;destFile.write(b, 0, read);downloaded.addAndGet(read);}BitUtil.setBit(blockSet, blockBegin, true); // 标记已经下载完成}blockBegin++;}response.getEntity().consumeContent();log.info(getThreadName() + "下载完成.");return;} catch (Exception e) {log.error(getThreadName() + "下载错误:" + e.getMessage());e.printStackTrace();} finally {try {if (inputStream != null)inputStream.close();} catch (Exception te) {log.error(te);}try {if (destFile != null)destFile.close();} catch (Exception te) {log.error(te);}}}}// 监控线程,并保存进度，方便下次断点续传private class MonitorThread extends Thread {boolean stop = false;public void setStop(boolean stop) {this.stop = stop;}public void run() {FileOutputStream saveStream = null;try {saveStream = new FileOutputStream(lockFile);while (running && !stop) {log.info(getDesc());// 保存进度saveStream.write(blockSet);sleep(1000);}} catch (Exception e) {log.error(e);} finally {if (saveStream != null) {try {saveStream.close();} catch (Exception e) {log.error(e);}}}}}// 用来操作位的工具private static class BitUtil {public static byte[] createBit(int len) {int size = len / Byte.SIZE;if (len % Byte.SIZE > 0) {size++;}return new byte[size];}/** 取出某位，是0 还是1 */public static boolean getBit(byte[] bits, int pos) {int i = pos / Byte.SIZE;int b = bits[i];int j = pos % Byte.SIZE;byte c = (byte) (0x80 >>> (j - 1));return b == c;}/** 设置某位，是0 还是1 */public static void setBit(byte[] bits, int pos, boolean flag) {int i = pos / Byte.SIZE;byte b = bits[i];int j = pos % Byte.SIZE;byte c = (byte) (0x80 >>> (j - 1));if (flag) {bits[i] = (byte) (b | c);} else {c = (byte) (0xFF ^ c);bits[i] = (byte) (b & c);}}}}

 

点击这里下载代码

 

使用测试

/** * 专注互联网,分享创造价值 * [e-mail] * 2010-3-31下午10:55:16 */package common.http;public class TestDownloader {public static void main(String[] args) throws Exception {String url = "http://apache.etoak.com/tomcat/tomcat-6/v6.0.26/bin/apache-tomcat-6.0.26.zip";String saveFile = "f:/tomcat.zip";HttpDownloader downloader = new HttpDownloader(url, saveFile);downloader.download();System.out.println("finsihed");}}