java多线程文件下载
1、DownloadManager类
import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.HttpURLConnection;import java.net.MalformedURLException;import java.net.URL;import java.util.ArrayList;import java.util.List;public class DownloadManager implements Runnable {// 保存路径private String savePath;// 总的下载线程数private int threadNum;// 下载的链接地址private String urlFile;// 是否下载开始private boolean isStarted;// 用于监视何时合并文件存放Thread的listprivate List<DownloadThread> downloadList = new ArrayList<DownloadThread>();public DownloadManager(String savePath, int threadNum, String urlFile) {super();this.savePath = savePath;this.threadNum = threadNum;this.urlFile = urlFile;}// 最终调用线程下载。本线程中调用分线程。public void action() {new Thread(this).start();}public void run() {long t1 = System.currentTimeMillis();System.out.println(t1);// 如果没有下载 ， 就开始 ， 并且将已经下载的变量值设为trueif (!isStarted) {startDownload();isStarted = true;}while (true) {// 初始化认为所有线程下载完成，逐个检查boolean finish = true;// 如果有任何一个没完成，说明下载没完成，不能合并文件for (DownloadThread thread : downloadList) {if (!thread.isFinish()) {finish = false;break;}}// 全部下载完成才为真if (finish) {// 合并文件mergeFiles();// 跳出循环 ， 下载结束break;}// 休息一会 ， 减少cpu消耗try {Thread.sleep(1000);} catch (InterruptedException e) {e.printStackTrace();}}long t2 = System.currentTimeMillis();System.out.println(t2); System.out.println("下载用时：" + (t2 -t1));}public void startDownload() {// 得到每个线程开始值 ， 下载字节数大小int[][] posAndLength = getPosAndLength();// 根据下载信息创建每个下载线程，并且启动他们。for (int i = 0; i < posAndLength.length; i++) {int pos = posAndLength[i][0];int length = posAndLength[i][1];DownloadThread downloadThread = new DownloadThread(i + 1, length,pos, savePath, urlFile);new Thread(downloadThread).start();downloadList.add(downloadThread);}}/** * 获得文件大小 * * @return 文件大小 */public long getFileLength() {System.out.println("获得文件大小 start......");HttpURLConnection conn = null;long result = 0;try {URL url = new URL(urlFile);conn = (HttpURLConnection) url.openConnection();// 使用Content-Length头信息获得文件大小result = Long.parseLong(conn.getHeaderField("Content-Length"));} catch (MalformedURLException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {if (conn != null) {conn.disconnect();}}System.out.println("获得文件大小 end......" + result);return result;}// 具体细节求出每个线程的开始位置和文件下载大小public int[][] getPosAndLength() {int[][] result = new int[threadNum][2];int fileLength = (int) getFileLength();int every = fileLength % threadNum == 0 ? fileLength / threadNum: fileLength / threadNum + 1;for (int i = 0; i < result.length; i++) {int length = 0;if (i != result.length - 1) {length = every;} else {length = fileLength - i * every;}result[i][0] = i * every;result[i][1] = length;}return result;}// 合并文件public void mergeFiles() {System.out.println("合并文件 start......");OutputStream out = null;try {out = new FileOutputStream(savePath);for (int i = 1; i <= threadNum; i++) {InputStream in = new FileInputStream(savePath + i);byte[] bytes = new byte[2048];int read = 0;while ((read = in.read(bytes)) != -1) {out.write(bytes, 0, read);out.flush();}if (in != null) {in.close();new File(savePath + i).delete();}}} catch (Exception e) {e.printStackTrace();} finally {if (out != null) {try {out.close();} catch (IOException e) {e.printStackTrace();}}}System.out.println("合并文件 end......");}public String getSavePath() {return savePath;}public void setSavePath(String savePath) {this.savePath = savePath;}public int getThreadNum() {return threadNum;}public void setThreadNum(int threadNum) {this.threadNum = threadNum;}public String getUrlFile() {return urlFile;}public void setUrlFile(String urlFile) {this.urlFile = urlFile;}public boolean isStarted() {return isStarted;}public void setStarted(boolean isStarted) {this.isStarted = isStarted;}public List<DownloadThread> getDownloadList() {return downloadList;}public void setDownloadList(List<DownloadThread> downloadList) {this.downloadList = downloadList;}}2、DownloadThread类
import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.HttpURLConnection;import java.net.URL;public class DownloadThread implements Runnable {// 当前第几个线程 ， 用于给下载文件起名 file1 file2 file3 ...private int whichThread;// 监听单一线程下载是否完成private boolean isFinish;// 本线程要下载的文件字节数private int length;// 本线程向服务器发送请求时输入流的首位置private int startPosition;// 保存的路径private String savePath;// 要下载的文件 ， 用于创建连接private String url;public void run() {HttpURLConnection conn = null;InputStream in = null;OutputStream out = null;try {System.out.println("正在执行的线程：" + whichThread);URL fileUrl = new URL(url);// 与服务器创建连接conn = (HttpURLConnection) fileUrl.openConnection();// 下载使用get请求conn.setRequestMethod("GET");// 告诉服务器 ， 我是火狐 ， 不要不让我下载。conn.setRequestProperty("User-Agent","Firefox Mozilla/5.0 (Windows; U; Windows NT 5.1; zh-CN; rv:1.9.1.3) Gecko/20090824 Firefox/3.5.3");// 这里是设置文件输入流的首位置conn.setRequestProperty("Range", "bytes=" + startPosition + "-");// 与服务器创建连接conn.connect();// 获得输入流in = conn.getInputStream();// 在硬盘上创建file1 , file2 , ...这样的文件 ， 准备往里面写东西out = new FileOutputStream(savePath + whichThread);// 用于写入的字节数组byte[] bytes = new byte[4096];// 一共下载了多少字节int count = 0;// 单次读取的字节数int read = 0;while ((read = in.read(bytes)) != -1) {// 检查一下是不是下载到了本线程需要的长度if (length - count < bytes.length) {// 比如说本线程还需要900字节，但是已经读取1000// 字节，则用要本线程总下载长度减去// 已经下载的长度read = length - count;}// 将准确的字节写入输出流out.write(bytes, 0, read);// 已经下载的字节数加上本次循环字节数count = count + read;// 如果下载字节达到本线程所需要字节数，消除循环，// 停止下载if (count == length) {break;}}// 将监视变量设置为trueisFinish = true;} catch (Exception e) {e.printStackTrace();} finally {// 最后进行输入、输出、连接的关闭if (in != null) {try {in.close();} catch (IOException e) {e.printStackTrace();}}if (out != null) {try {out.close();} catch (IOException e) {e.printStackTrace();}}if (conn != null) {conn.disconnect();}}}public int getStartPosition() {return startPosition;}public void setStartPosition(int startPosition) {this.startPosition = startPosition;}public String getUrl() {return url;}public void setUrl(String url) {this.url = url;}public int getWhichThread() {return whichThread;}public void setWhichThread(int whichThread) {this.whichThread = whichThread;}public int getLength() {return length;}public void setLength(int length) {this.length = length;}public String getSavePath() {return savePath;}public void setSavePath(String savePath) {this.savePath = savePath;}public DownloadThread(int whichThread, int length, int startPosition,String savePath, String url) {super();this.whichThread = whichThread;this.length = length;this.startPosition = startPosition;this.savePath = savePath;this.url = url;}public DownloadThread() {super();}public boolean isFinish() {return isFinish;}public void setFinish(boolean isFinish) {this.isFinish = isFinish;}}3、TestDownload测试类
public class TestDownload {public static void main(String[] args) {DownloadManager downloadManager = new DownloadManager("d:/upload/09018417.zip" , 5 , "http://10.1.2.65:8080/cetvossFront/09018417.zip");downloadManager.action();}}转自：
http://ljlleo.iteye.com/blog/1397765