java 多线程断点下载文件

下载文件信息类、实体

封装即将下载资源的信息

package com.hoo.entity;

/**

* function: 下载文件信息类

* @author hoojo

* @createDate 2011-9-21 下午05:14:58

* @file DownloadInfo.java

* @package com.hoo.entity

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public class DownloadInfo {

 //下载文件url

 private String url;

 //下载文件名称

 private String fileName;

 //下载文件路径

 private String filePath;

 //分成多少段下载，每一段用一个线程完成下载

 private int splitter;



 //下载文件默认保存路径

 private final static String FILE_PATH = "C:/temp";

 //默认分块数、线程数

 private final static int SPLITTER_NUM = 5;



 public DownloadInfo() {

 super();

 }



 /**

 * @param url 下载地址

 */

 public DownloadInfo(String url) {

 this(url, null, null, SPLITTER_NUM);

 }



 /**

 * @param url 下载地址url

 * @param splitter 分成多少段或是多少个线程下载

 */

 public DownloadInfo(String url, int splitter) {

 this(url, null, null, splitter);

 }



 /***

 * @param url 下载地址

 * @param fileName 文件名称

 * @param filePath 文件保存路径

 * @param splitter 分成多少段或是多少个线程下载

 */

 public DownloadInfo(String url, String fileName, String filePath, int splitter) {

 super();

 if (url == null || "".equals(url)) {

 throw new RuntimeException("url is not null!");

 }

 this.url = url;

 this.fileName = (fileName == null || "".equals(fileName)) ? getFileName(url) : fileName;

 this.filePath = (filePath == null || "".equals(filePath)) ? FILE_PATH : filePath;

 this.splitter = (splitter < 1) ? SPLITTER_NUM : splitter;

 }



 /**

 * function: 通过url获得文件名称

 * @author hoojo

 * @createDate 2011-9-30 下午05:00:00

 * @param url

 * @return

 */

 private String getFileName(String url) {

 return url.substring(url.lastIndexOf("/") + 1, url.length());

 }



 public String getUrl() {

 return url;

 }

 public void setUrl(String url) {

 if (url == null || "".equals(url)) {

 throw new RuntimeException("url is not null!");

 }

 this.url = url;

 }

 public String getFileName() {

 return fileName;

 }

 public void setFileName(String fileName) {

 this.fileName = (fileName == null || "".equals(fileName)) ? getFileName(url) : fileName;

 }

 public String getFilePath() {

 return filePath;

 }

 public void setFilePath(String filePath) {

 this.filePath = (filePath == null || "".equals(filePath)) ? FILE_PATH : filePath;

 }

 public int getSplitter() {

 return splitter;

 }

 public void setSplitter(int splitter) {

 this.splitter = (splitter < 1) ? SPLITTER_NUM : splitter;

 }



 @Override

 public String toString() {

 return this.url + "#" + this.fileName + "#" + this.filePath + "#" + this.splitter;

 }

}

二、随机写入一段文件

package com.hoo.download;

import java.io.IOException;

import java.io.RandomAccessFile;

/**

* function: 写入文件、保存文件

* @author hoojo

* @createDate 2011-9-21 下午05:44:02

* @file SaveItemFile.java

* @package com.hoo.download

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public class SaveItemFile {

 //存储文件

 private RandomAccessFile itemFile;



 public SaveItemFile() throws IOException {

 this("", 0);

 }



 /**

 * @param name 文件路径、名称

 * @param pos 写入点位置 position

 * @throws IOException

 */

 public SaveItemFile(String name, long pos) throws IOException {

 itemFile = new RandomAccessFile(name, "rw");

 //在指定的pos位置开始写入数据

 itemFile.seek(pos);

 }



 /**

 * function: 同步方法写入文件

 * @author hoojo

 * @createDate 2011-9-26 下午12:21:22

 * @param buff 缓冲数组

 * @param start 起始位置

 * @param length 长度

 * @return

 */

 public synchronized int write(byte[] buff, int start, int length) {

 int i = -1;

 try {

 itemFile.write(buff, start, length);

 i = length;

 } catch (IOException e) {

 e.printStackTrace();

 }

 return i;

 }



 public void close() throws IOException {

 if (itemFile != null) {

 itemFile.close();

 }

 }

}

这个类主要是完成向本地的指定文件指针出开始写入文件，并返回当前写入文件的长度（文件指针）。这个类将被线程调用，文件被分成对应的块后，将被线程调用。每个线程都将会调用这个类完成文件的随机写入。

三、单个线程下载文件

package com.hoo.download;

import java.io.IOException;

import java.io.InputStream;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import java.net.URLConnection;

import com.hoo.util.LogUtils;

/**

* function: 单线程下载文件

* @author hoojo

* @createDate 2011-9-22 下午02:55:10

* @file DownloadFile.java

* @package com.hoo.download

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public class DownloadFile extends Thread {



 //下载文件url

 private String url;

 //下载文件起始位置

 private long startPos;

 //下载文件结束位置

 private long endPos;

 //线程id

 private int threadId;



 //下载是否完成

 private boolean isDownloadOver = false;

 private SaveItemFile itemFile;



 private static final int BUFF_LENGTH = 1024 * 8;



 /**

 * @param url 下载文件url

 * @param name 文件名称

 * @param startPos 下载文件起点

 * @param endPos 下载文件结束点

 * @param threadId 线程id

 * @throws IOException

 */

 public DownloadFile(String url, String name, long startPos, long endPos, int threadId) throws IOException {

 super();

 this.url = url;

 this.startPos = startPos;

 this.endPos = endPos;

 this.threadId = threadId;

 //分块下载写入文件内容

 this.itemFile = new SaveItemFile(name, startPos);

 }



 @Override

 public void run() {

 while (endPos > startPos && !isDownloadOver) {

 try {

 URL url = new URL(this.url);

 HttpURLConnection conn = (HttpURLConnection) url.openConnection();



 // 设置连接超时时间为10000ms

 conn.setConnectTimeout(10000);

 // 设置读取数据超时时间为10000ms

 conn.setReadTimeout(10000);



 setHeader(conn);



 String property = "bytes=" + startPos + "-";

 conn.setRequestProperty("RANGE", property);



 //输出log信息

 LogUtils.log("开始 " + threadId + "：" + property + endPos);

 //printHeader(conn);



 //获取文件输入流，读取文件内容

 InputStream is = conn.getInputStream();



 byte[] buff = new byte[BUFF_LENGTH];

 int length = -1;

 LogUtils.log("#start#Thread: " + threadId + ", startPos: " + startPos + ", endPos: " + endPos);

 while ((length = is.read(buff)) > 0 && startPos < endPos && !isDownloadOver) {

 //写入文件内容，返回最后写入的长度

 startPos += itemFile.write(buff, 0, length);

 }

 LogUtils.log("#over#Thread: " + threadId + ", startPos: " + startPos + ", endPos: " + endPos);

 LogUtils.log("Thread " + threadId + " is execute over!");

 this.isDownloadOver = true;

 } catch (MalformedURLException e) {

 e.printStackTrace();

 } catch (IOException e) {

 e.printStackTrace();

 } finally {

 try {

 if (itemFile != null) {

 itemFile.close();

 }

 } catch (IOException e) {

 e.printStackTrace();

 }

 }

 }

 if (endPos < startPos && !isDownloadOver) {

 LogUtils.log("Thread " + threadId + " startPos > endPos, not need download file !");

 this.isDownloadOver = true;

 }

 if (endPos == startPos && !isDownloadOver) {

 LogUtils.log("Thread " + threadId + " startPos = endPos, not need download file !");

 this.isDownloadOver = true;

 }

 }



 /**

 * function: 打印下载文件头部信息

 * @author hoojo

 * @createDate 2011-9-22 下午05:44:35

 * @param conn HttpURLConnection

 */

 public static void printHeader(URLConnection conn) {

 int i = 1;

 while (true) {

 String header = conn.getHeaderFieldKey(i);

 i++;

 if (header != null) {

 LogUtils.info(header + ":" + conn.getHeaderField(i));

 } else {

 break;

 }

 }

 }



 /**

 * function: 设置URLConnection的头部信息，伪装请求信息

 * @author hoojo

 * @createDate 2011-9-28 下午05:29:43

 * @param con

 */

 public static void setHeader(URLConnection conn) {

 conn.setRequestProperty("User-Agent", "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.3) Gecko/2008092510 Ubuntu/8.04 (hardy) Firefox/3.0.3");

 conn.setRequestProperty("Accept-Language", "en-us,en;q=0.7,zh-cn;q=0.3");

 conn.setRequestProperty("Accept-Encoding", "utf-8");

 conn.setRequestProperty("Accept-Charset", "ISO-8859-1,utf-8;q=0.7,*;q=0.7");

 conn.setRequestProperty("Keep-Alive", "300");

 conn.setRequestProperty("connnection", "keep-alive");

 conn.setRequestProperty("If-Modified-Since", "Fri, 02 Jan 2009 17:00:05 GMT");

 conn.setRequestProperty("If-None-Match", "\"1261d8-4290-df64d224\"");

 conn.setRequestProperty("Cache-conntrol", "max-age=0");

 conn.setRequestProperty("Referer", "http://www.baidu.com");

 }



 public boolean isDownloadOver() {

 return isDownloadOver;

 }



 public long getStartPos() {

 return startPos;

 }

 public long getEndPos() {

 return endPos;

 }

}

这个类主要是完成单个线程的文件下载，将通过URLConnection读取指定url的资源信息。然后用InputStream读取文件内容，然后调用调用SaveItemFile类，向本地写入当前要读取的块的内容。

四、分段多线程写入文件内容

package com.hoo.download;

import java.io.DataInputStream;

import java.io.DataOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileOutputStream;

import java.io.IOException;

import java.net.HttpURLConnection;

import java.net.MalformedURLException;

import java.net.URL;

import com.hoo.entity.DownloadInfo;

import com.hoo.util.LogUtils;

/**

* function: 分批量下载文件

* @author hoojo

* @createDate 2011-9-22 下午05:51:54

* @file BatchDownloadFile.java

* @package com.hoo.download

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public class BatchDownloadFile implements Runnable {

 //下载文件信息

 private DownloadInfo downloadInfo;

 //一组开始下载位置

 private long[] startPos;

 //一组结束下载位置

 private long[] endPos;

 //休眠时间

 private static final int SLEEP_SECONDS = 500;

 //子线程下载

 private DownloadFile[] fileItem;

 //文件长度

 private int length;

 //是否第一个文件

 private boolean first = true;

 //是否停止下载

 private boolean stop = false;

 //临时文件信息

 private File tempFile;



 public BatchDownloadFile(DownloadInfo downloadInfo) {

 this.downloadInfo = downloadInfo;

 String tempPath = this.downloadInfo.getFilePath() + File.separator + downloadInfo.getFileName() + ".position";

 tempFile = new File(tempPath);

 //如果存在读入点位置的文件

 if (tempFile.exists()) {

 first = false;

 //就直接读取内容

 try {

 readPosInfo();

 } catch (IOException e) {

 e.printStackTrace();

 }

 } else {

 //数组的长度就要分成多少段的数量

 startPos = new long[downloadInfo.getSplitter()];

 endPos = new long[downloadInfo.getSplitter()];

 }

 }



 @Override

 public void run() {

 //首次下载，获取下载文件长度

 if (first) {

 length = this.getFileSize();//获取文件长度

 if (length == -1) {

 LogUtils.log("file length is know!");

 stop = true;

 } else if (length == -2) {

 LogUtils.log("read file length is error!");

 stop = true;

 } else if (length > 0) {

 /**

 * eg

 * start: 1, 3, 5, 7, 9

 * end: 3, 5, 7, 9, length

 */

 for (int i = 0, len = startPos.length; i < len; i++) {

 int size = i * (length / len);

 startPos[i] = size;



 //设置最后一个结束点的位置

 if (i == len - 1) {

 endPos[i] = length;

 } else {

 size = (i + 1) * (length / len);

 endPos[i] = size;

 }

 LogUtils.log("start-end Position[" + i + "]: " + startPos[i] + "-" + endPos[i]);

 }

 } else {

 LogUtils.log("get file length is error, download is stop!");

 stop = true;

 }

 }



 //子线程开始下载

 if (!stop) {

 //创建单线程下载对象数组

 fileItem = new DownloadFile[startPos.length];//startPos.length = downloadInfo.getSplitter()

 for (int i = 0; i < startPos.length; i++) {

 try {

 //创建指定个数单线程下载对象，每个线程独立完成指定块内容的下载

 fileItem[i] = new DownloadFile(

 downloadInfo.getUrl(),

 this.downloadInfo.getFilePath() + File.separator + downloadInfo.getFileName(),

 startPos[i], endPos[i], i

 );

 fileItem[i].start();//启动线程，开始下载

 LogUtils.log("Thread: " + i + ", startPos: " + startPos[i] + ", endPos: " + endPos[i]);

 } catch (IOException e) {

 e.printStackTrace();

 }

 }



 //循环写入下载文件长度信息

 while (!stop) {

 try {

 writePosInfo();

 LogUtils.log("downloading……");

 Thread.sleep(SLEEP_SECONDS);

 stop = true;

 } catch (IOException e) {

 e.printStackTrace();

 } catch (InterruptedException e) {

 e.printStackTrace();

 }

 for (int i = 0; i < startPos.length; i++) {

 if (!fileItem[i].isDownloadOver()) {

 stop = false;

 break;

 }

 }

 }

 LogUtils.info("Download task is finished!");

 }

 }



 /**

 * 将写入点数据保存在临时文件中

 * @author hoojo

 * @createDate 2011-9-23 下午05:25:37

 * @throws IOException

 */

 private void writePosInfo() throws IOException {

 DataOutputStream dos = new DataOutputStream(new FileOutputStream(tempFile));

 dos.writeInt(startPos.length);

 for (int i = 0; i < startPos.length; i++) {

 dos.writeLong(fileItem[i].getStartPos());

 dos.writeLong(fileItem[i].getEndPos());

 //LogUtils.info("[" + fileItem[i].getStartPos() + "#" + fileItem[i].getEndPos() + "]");

 }

 dos.close();

 }



 /**

 * function:读取写入点的位置信息

 * @author hoojo

 * @createDate 2011-9-23 下午05:30:29

 * @throws IOException

 */

 private void readPosInfo() throws IOException {

 DataInputStream dis = new DataInputStream(new FileInputStream(tempFile));

 int startPosLength = dis.readInt();

 startPos = new long[startPosLength];

 endPos = new long[startPosLength];

 for (int i = 0; i < startPosLength; i++) {

 startPos[i] = dis.readLong();

 endPos[i] = dis.readLong();

 }

 dis.close();

 }



 /**

 * function: 获取下载文件的长度

 * @author hoojo

 * @createDate 2011-9-26 下午12:15:08

 * @return

 */

 private int getFileSize() {

 int fileLength = -1;

 try {

 URL url = new URL(this.downloadInfo.getUrl());

 HttpURLConnection conn = (HttpURLConnection) url.openConnection();



 DownloadFile.setHeader(conn);

 int stateCode = conn.getResponseCode();

 //判断http status是否为HTTP/1.1 206 Partial Content或者200 OK

 if (stateCode != HttpURLConnection.HTTP_OK && stateCode != HttpURLConnection.HTTP_PARTIAL) {

 LogUtils.log("Error Code: " + stateCode);

 return -2;

 } else if (stateCode >= 400) {

 LogUtils.log("Error Code: " + stateCode);

 return -2;

 } else {

 //获取长度

 fileLength = conn.getContentLength();

 LogUtils.log("FileLength: " + fileLength);

 }



 //读取文件长度

 /*for (int i = 1; ; i++) {

 String header = conn.getHeaderFieldKey(i);

 if (header != null) {

 if ("Content-Length".equals(header)) {

 fileLength = Integer.parseInt(conn.getHeaderField(i));

 break;

 }

 } else {

 break;

 }

 }

 */



 DownloadFile.printHeader(conn);

 } catch (MalformedURLException e) {

 e.printStackTrace();

 } catch (IOException e) {

 e.printStackTrace();

 }

 return fileLength;

 }

}

这个类主要是完成读取指定url资源的内容，获取该资源的长度。然后将该资源分成指定的块数，将每块的起始下载位置、结束下载位置，分别保存在一个数组中。每块都单独开辟一个独立线程开始下载。在开始下载之前，需要创建一个临时文件，写入当前下载线程的开始下载指针位置和结束下载指针位置。

五、工具类、测试类

日志工具类

package com.hoo.util;

/**

* function: 日志工具类

* @author hoojo

* @createDate 2011-9-21 下午05:21:27

* @file LogUtils.java

* @package com.hoo.util

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public abstract class LogUtils {



 public static void log(Object message) {

 System.err.println(message);

 }



 public static void log(String message) {

 System.err.println(message);

 }



 public static void log(int message) {

 System.err.println(message);

 }



 public static void info(Object message) {

 System.out.println(message);

 }



 public static void info(String message) {

 System.out.println(message);

 }



 public static void info(int message) {

 System.out.println(message);

 }

}

下载工具类

package com.hoo.util;

import com.hoo.download.BatchDownloadFile;

import com.hoo.entity.DownloadInfo;

/**

* function: 分块多线程下载工具类

* @author hoojo

* @createDate 2011-9-28 下午05:22:18

* @file DownloadUtils.java

* @package com.hoo.util

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public abstract class DownloadUtils {

 public static void download(String url) {

 DownloadInfo bean = new DownloadInfo(url);

 LogUtils.info(bean);

 BatchDownloadFile down = new BatchDownloadFile(bean);

 new Thread(down).start();

 }



 public static void download(String url, int threadNum) {

 DownloadInfo bean = new DownloadInfo(url, threadNum);

 LogUtils.info(bean);

 BatchDownloadFile down = new BatchDownloadFile(bean);

 new Thread(down).start();

 }



 public static void download(String url, String fileName, String filePath, int threadNum) {

 DownloadInfo bean = new DownloadInfo(url, fileName, filePath, threadNum);

 LogUtils.info(bean);

 BatchDownloadFile down = new BatchDownloadFile(bean);

 new Thread(down).start();

 }

}

下载测试类

package com.hoo.test;

import com.hoo.util.DownloadUtils;

/**

* function: 下载测试

* @author hoojo

* @createDate 2011-9-23 下午05:49:46

* @file TestDownloadMain.java

* @package com.hoo.download

* @project MultiThreadDownLoad

* @blog http://blog.csdn.net/IBM_hoojo

* @email [email protected]

* @version 1.0

*/

public class TestDownloadMain {

 public static void main(String[] args) {

 /*DownloadInfo bean = new DownloadInfo("http://i7.meishichina.com/Health/UploadFiles/201109/2011092116224363.jpg");

 System.out.println(bean);

 BatchDownloadFile down = new BatchDownloadFile(bean);

 new Thread(down).start();*/



 //DownloadUtils.download("http://i7.meishichina.com/Health/UploadFiles/201109/2011092116224363.jpg");

 DownloadUtils.download("http://mp3.baidu.com/j?j=2&url=http%3A%2F%2Fzhangmenshiting2.baidu.com%2Fdata%2Fmusic%2F1669425%2F%25E9%2599%25B7%25E5%2585%25A5%25E7%2588%25B1%25E9%2587%258C%25E9%259D%25A2.mp3%3Fxcode%3D2ff36fb70737c816553396c56deab3f1", "aa.mp3", "c:/temp", 5);

 }

}

多线程下载主要在第三部和第四部，其他的地方还是很好理解。源码中提供相应的注释了，便于理解。
转http://www.cnblogs.com/hoojo/archive/2011/09/30/2196767.html

java 多线程断点下载文件

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