本文轉載于：http://blog.csdn.net/ibm_hoojo/article/details/6838222
基本原理：利用URLConnection獲取要下載文件的長度、頭部等相關信息，并設置響應的頭部信息。并且通過URLConnection獲取輸入流，將文件分成指定的塊，每一塊單獨開辟一個線程完成數據的讀取、寫入。通過輸入流讀取下載文件的信息，然后將讀取的信息用RandomAccessFile隨機寫入到本地文件中。同時，每個線程寫入的數據都文件指針也就是寫入數據的長度，需要保存在一個臨時文件中。這樣當本次下載沒有完成的時候，下次下載的時候就從這個文件中讀取上一次下載的文件長度，然后繼續接著上一次的位置開始下載。并且將本次下載的長度寫入到這個文件中。
個人博客：
http://hoojo.cnblogs.com
http://blog.csdn.net/IBM_hoojo
email: hoojo_@126.com
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一、下載文件信息類、實體
封裝即將下載資源的信息
[java] view plaincopyprint?
package com.hoo.entity;?? ? public class DownloadInfo {???? ? ??? private String url;? ??? ? ??? private String fileName;? ??? ? ??? private String filePath;? ??? ???? private int splitter;?????? ??? ? ??? private finalstatic String FILE_PATH = "C:/temp";???? ? ??? private finalstatic int SPLITTER_NUM =5;? ????? ??? public DownloadInfo() {???????? super();? ??? }? ????? ??? ? ??? public DownloadInfo(String url) {???????? this(url, null, null, SPLITTER_NUM);???? }? ????? ??? ? ??? public DownloadInfo(String url, int splitter) {? ??????? this(url, null, null, splitter);???? }? ????? ??? ? ??? 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;? ??? }? ????? ??? ? ??? 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;???? }? }? package com.hoo.entity;/*** <b>function:</b> 下載文件信息類* @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 hoojo_@126.com* @version 1.0*/
public class DownloadInfo {//下載文件urlprivate String url;//下載文件名稱private String fileName;//下載文件路徑private String filePath;//分成多少段下載， 每一段用一個線程完成下載private int splitter;//下載文件默認保存路徑private final static String FILE_PATH = "C:/temp";//默認分塊數、線程數private final static int SPLITTER_NUM = 5;public DownloadInfo() {super();}/*** @param url 下載地址*/public DownloadInfo(String url) {this(url, null, null, SPLITTER_NUM);}/*** @param url 下載地址url* @param splitter 分成多少段或是多少個線程下載*/public DownloadInfo(String url, int splitter) {this(url, null, null, splitter);}/**** @param url 下載地址* @param fileName 文件名稱* @param filePath 文件保存路徑* @param splitter 分成多少段或是多少個線程下載*/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;}/*** <b>function:</b> 通過url獲得文件名稱* @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;}@Overridepublic String toString() {return this.url + "#" + this.fileName + "#" + this.filePath + "#" + this.splitter;}
}
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二、隨機寫入一段文件
[java] view plaincopyprint?
package com.hoo.download;?? import java.io.IOException;?import java.io.RandomAccessFile;? ? ? public class SaveItemFile {???? ? ??? private RandomAccessFile itemFile;?????? ??? public SaveItemFile()throws IOException {? ??????? this("",0);? ??? }? ????? ??? ? ??? public SaveItemFile(String name,long pos) throws IOException {???????? itemFile = new RandomAccessFile(name,"rw");? ??????? ? ??????? itemFile.seek(pos);? ??? }? ????? ??? ? ??? public synchronizedint 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();? ??????? }? ??? }? }? package com.hoo.download;import java.io.IOException;
import java.io.RandomAccessFile;/*** <b>function:</b> 寫入文件、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 hoojo_@126.com* @version 1.0*/
public class SaveItemFile {//存儲文件private RandomAccessFile itemFile;public SaveItemFile() throws IOException {this("", 0);}/*** @param name 文件路徑、名稱* @param pos 寫入點位置 position* @throws IOException*/public SaveItemFile(String name, long pos) throws IOException {itemFile = new RandomAccessFile(name, "rw");//在指定的pos位置開始寫入數據itemFile.seek(pos);}/*** <b>function:</b> 同步方法寫入文件* @author hoojo* @createDate 2011-9-26 下午12:21:22* @param buff 緩沖數組* @param start 起始位置* @param length 長度* @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();}}
}
這個類主要是完成向本地的指定文件指針出開始寫入文件，并返回當前寫入文件的長度（文件指針）。這個類將被線程調用，文件被分成對應的塊后，將被線程調用。每個線程都將會調用這個類完成文件的隨機寫入。
三、單個線程下載文件
[java] view plaincopyprint?
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;?? ? public class DownloadFileextends Thread {? ????? ??? ? ??? private String url;???? ? ??? private long startPos;???? ? ??? private long endPos;???? ? ??? private int threadId;?????? ??? ? ??? private boolean isDownloadOver =false;? ? ??? private SaveItemFile itemFile;? ????? ??? private staticfinal int BUFF_LENGTH =1024 * 8;?????? ??? ? ??? 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;???????? ? ??????? 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();?????????????????? ??????????????? ???????????????? conn.setConnectTimeout(10000);???????????????? ???????????????? conn.setReadTimeout(10000);?????????????????? ??????????????? setHeader(conn);? ????????????????? ??????????????? String property = "bytes=" + startPos +"-";? ??????????????? conn.setRequestProperty("RANGE", property);?????????????????? ??????????????? ? ??????????????? LogUtils.log("開始 " + threadId +"：" + property + endPos);? ??????????????? ?????????????????? ??????????????? ? ??????????????? 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) {???????????????????? ???????????????????? 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;? ??????? }? ??? }? ????? ??? ? ??? public staticvoid 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;? ??????????? }? ??????? }? ??? }? ????? ??? ? ??? public staticvoid 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;? ??? }? }? 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;/*** <b>function:</b> 單線程下載文件* @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 hoojo_@126.com* @version 1.0*/
public class DownloadFile extends Thread {//下載文件urlprivate String url;//下載文件起始位置 private long startPos;//下載文件結束位置private long endPos;//線程idprivate int threadId;//下載是否完成private boolean isDownloadOver = false;private SaveItemFile itemFile;private static final int BUFF_LENGTH = 1024 * 8;/*** @param url 下載文件url* @param name 文件名稱* @param startPos 下載文件起點* @param endPos 下載文件結束點* @param threadId 線程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;//分塊下載寫入文件內容this.itemFile = new SaveItemFile(name, startPos);}@Overridepublic void run() {while (endPos > startPos && !isDownloadOver) {try {URL url = new URL(this.url);HttpURLConnection conn = (HttpURLConnection) url.openConnection();// 設置連接超時時間為10000msconn.setConnectTimeout(10000);// 設置讀取數據超時時間為10000msconn.setReadTimeout(10000);setHeader(conn);String property = "bytes=" + startPos + "-";conn.setRequestProperty("RANGE", property);//輸出log信息LogUtils.log("開始 " + threadId + "：" + property + endPos);//printHeader(conn);//獲取文件輸入流，讀取文件內容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) {//寫入文件內容，返回最后寫入的長度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;}}/*** <b>function:</b> 打印下載文件頭部信息* @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;}}}/*** <b>function:</b> 設置URLConnection的頭部信息，偽裝請求信息* @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;}
}
這個類主要是完成單個線程的文件下載，將通過URLConnection讀取指定url的資源信息。然后用InputStream讀取文件內容，然后調用調用SaveItemFile類，向本地寫入當前要讀取的塊的內容。
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四、分段多線程寫入文件內容
[java] view plaincopyprint?
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;?? ? public class BatchDownloadFileimplements Runnable {? ??? ? ??? private DownloadInfo downloadInfo;???? ? ??? private long[] startPos;???? ? ??? private long[] endPos;???? ? ??? private staticfinal int SLEEP_SECONDS =500;? ??? ? ??? private DownloadFile[] fileItem;???? ? ??? private int length;???? ? ??? private boolean first =true;? ??? ? ??? private boolean stop =false;? ??? ? ??? private File tempFile;? ????? ??? public BatchDownloadFile(DownloadInfo downloadInfo) {???????? this.downloadInfo = downloadInfo;???????? String tempPath = this.downloadInfo.getFilePath() + File.separator + downloadInfo.getFileName() +".position";? ??????? tempFile = new File(tempPath);???????? ? ??????? if (tempFile.exists()) {???????????? first = false;? ??????????? ? ??????????? try {? ??????????????? readPosInfo();? ??????????? } catch (IOException e) {???????????????? e.printStackTrace();? ??????????? }? ??????? } else {? ??????????? ? ??????????? startPos = newlong[downloadInfo.getSplitter()];? ??????????? endPos = new long[downloadInfo.getSplitter()];???????? }? ??? }? ????? ??? @Override? ??? public void run() {???????? ? ??????? if (first) {? ??????????? length = this.getFileSize();???????????? 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) {???????????????? ? ??????????????? for (int i =0, len = startPos.length; i < len; i++) {???????????????????? int size = i * (length / len);???????????????????? startPos[i] = size;? ????????????????????? ??????????????????? ???????????????????? 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;? ??????????? }? ??????? }? ????????? ??????? ? ??????? if (!stop) {? ??????????? ? ??????????? fileItem = new DownloadFile[startPos.length];???????????? for (int i =0; i < startPos.length; i++) {? ??????????????? try {? ??????????????????? ???????????????????? fileItem[i] = new DownloadFile(???????????????????????? downloadInfo.getUrl(),?? ??????????????????????? this.downloadInfo.getFilePath() + File.separator + downloadInfo.getFileName(),????????????????????????? startPos[i], endPos[i], i? ??????????????????? );? ??????????????????? fileItem[i].start();???????????????????? LogUtils.log("Thread: " + i +", startPos: " + startPos[i] + ", endPos: " + endPos[i]);???????????????? } catch (IOException e) {???????????????????? e.printStackTrace();? ??????????????? }? ??????????? }? ????????????? ??????????? ???????????? 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!");???????? }? ??? }? ????? ??? ? ??? 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());? ??????????? ???????? }? ??????? dos.close();? ??? }? ????? ??? ? ??? 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();? ??? }? ????? ??? ? ??? 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();???????????? ???????????? 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 {? ??????????????? ? ??????????????? fileLength = conn.getContentLength();? ??????????????? LogUtils.log("FileLength: " + fileLength);???????????? }? ????????????? ??????????? ? ??????????? ? ????????????? ??????????? DownloadFile.printHeader(conn);? ??????? } catch (MalformedURLException e) {???????????? e.printStackTrace();? ??????? } catch (IOException e) {? ??????????? e.printStackTrace();? ??????? }? ??????? return fileLength;???? }? }? 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;/*** <b>function:</b> 分批量下載文件* @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 hoojo_@126.com* @version 1.0*/
public class BatchDownloadFile implements Runnable {//下載文件信息 private DownloadInfo downloadInfo;//一組開始下載位置private long[] startPos;//一組結束下載位置private long[] endPos;//休眠時間private static final int SLEEP_SECONDS = 500;//子線程下載private DownloadFile[] fileItem;//文件長度private int length;//是否第一個文件private boolean first = true;//是否停止下載private boolean stop = false;//臨時文件信息private File tempFile;public BatchDownloadFile(DownloadInfo downloadInfo) {this.downloadInfo = downloadInfo;String tempPath = this.downloadInfo.getFilePath() + File.separator + downloadInfo.getFileName() + ".position";tempFile = new File(tempPath);//如果存在讀入點位置的文件if (tempFile.exists()) {first = false;//就直接讀取內容try {readPosInfo();} catch (IOException e) {e.printStackTrace();}} else {//數組的長度就要分成多少段的數量startPos = new long[downloadInfo.getSplitter()];endPos = new long[downloadInfo.getSplitter()];}}@Overridepublic void run() {//首次下載，獲取下載文件長度if (first) {length = this.getFileSize();//獲取文件長度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;//設置最后一個結束點的位置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;}}//子線程開始下載if (!stop) {//創建單線程下載對象數組fileItem = new DownloadFile[startPos.length];//startPos.length = downloadInfo.getSplitter()for (int i = 0; i < startPos.length; i++) {try {//創建指定個數單線程下載對象，每個線程獨立完成指定塊內容的下載fileItem[i] = new DownloadFile(downloadInfo.getUrl(), this.downloadInfo.getFilePath() + File.separator + downloadInfo.getFileName(), startPos[i], endPos[i], i);fileItem[i].start();//啟動線程，開始下載LogUtils.log("Thread: " + i + ", startPos: " + startPos[i] + ", endPos: " + endPos[i]);} catch (IOException e) {e.printStackTrace();}}//循環寫入下載文件長度信息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!");}}/*** 將寫入點數據保存在臨時文件中* @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();}/*** <b>function:</b>讀取寫入點的位置信息* @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();}/*** <b>function:</b> 獲取下載文件的長度* @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();//判斷http status是否為HTTP/1.1 206 Partial Content或者200 OKif (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 {//獲取長度fileLength = conn.getContentLength();LogUtils.log("FileLength: " + fileLength);}//讀取文件長度/*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;}
}這個類主要是完成讀取指定url資源的內容，獲取該資源的長度。然后將該資源分成指定的塊數，將每塊的起始下載位置、結束下載位置，分別保存在一個數組中。每塊都單獨開辟一個獨立線程開始下載。在開始下載之前，需要創建一個臨時文件，寫入當前下載線程的開始下載指針位置和結束下載指針位置。
?
五、工具類、測試類
日志工具類
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package com.hoo.util;? ? ? public abstractclass LogUtils {? ????? ??? public staticvoid log(Object message) {? ??????? System.err.println(message);? ??? }? ????? ??? public staticvoid log(String message) {? ??????? System.err.println(message);? ??? }? ????? ??? public staticvoid log(int message) {???????? System.err.println(message);? ??? }? ????? ??? public staticvoid info(Object message) {? ??????? System.out.println(message);? ??? }? ????? ??? public staticvoid info(String message) {? ??????? System.out.println(message);? ??? }? ????? ??? public staticvoid info(int message) {???????? System.out.println(message);? ??? }? }? package com.hoo.util;/*** <b>function:</b> 日志工具類* @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 hoojo_@126.com* @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);}
}
下載工具類
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package com.hoo.util;? ? import com.hoo.download.BatchDownloadFile;?import com.hoo.entity.DownloadInfo;?? ? public abstractclass DownloadUtils {? ? ??? public staticvoid download(String url) {? ??????? DownloadInfo bean = new DownloadInfo(url);???????? LogUtils.info(bean);? ??????? BatchDownloadFile down = new BatchDownloadFile(bean);???????? new Thread(down).start();???? }? ????? ??? public staticvoid download(String url, int threadNum) {???????? DownloadInfo bean = new DownloadInfo(url, threadNum);???????? LogUtils.info(bean);? ??????? BatchDownloadFile down = new BatchDownloadFile(bean);???????? new Thread(down).start();? ??? }? ????? ??? public staticvoid 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();???? }? }? package com.hoo.util;import com.hoo.download.BatchDownloadFile;
import com.hoo.entity.DownloadInfo;/*** <b>function:</b> 分塊多線程下載工具類* @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 hoojo_@126.com* @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();}
}
下載測試類
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package com.hoo.test;? ? import com.hoo.util.DownloadUtils;?? ? public class TestDownloadMain {?? ??? public staticvoid main(String[] args) {? ??????? ?????????? ??????? ???????? 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);? ??? }? }? package com.hoo.test;import com.hoo.util.DownloadUtils;/*** <b>function:</b> 下載測試* @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 hoojo_@126.com* @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);}
}多線程下載主要在第三部和第四部，其他的地方還是很好理解。源碼中提供相應的注釋了，便于理解。
本文轉載于：http://blog.csdn.net/ibm_hoojo/article/details/6838222
轉載于:https://www.cnblogs.com/ouyangpeng/archive/2013/04/04/8538416.html
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