Java 多线程断点下载文件_详解

本文转载于：http://blog.csdn.net/ibm_hoojo/article/details/6838222

基本原理：利用URLConnection获取要下载文件的长度、头部等相关信息，并设置响应的头部信息。并且通过URLConnection获取输入流，将文件分成指定的块，每一块单独开辟一个线程完成数据的读取、写入。通过输入流读取下载文件的信息，然后将读取的信息用RandomAccessFile随机写入到本地文件中。同时，每个线程写入的数据都文件指针也就是写入数据的长度，需要保存在一个临时文件中。这样当本次下载没有完成的时候，下次下载的时候就从这个文件中读取上一次下载的文件长度，然后继续接着上一次的位置开始下载。并且将本次下载的长度写入到这个文件中。

个人博客：

http://hoojo.cnblogs.com

http://blog.csdn.net/IBM_hoojo

email: hoojo_@126.com

 

一、下载文件信息类、实体

封装即将下载资源的信息

[java] view plaincopyprint?

package com.hoo.entity; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @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 finalstatic String FILE_PATH = "C:/temp"; 

    //默认分块数、线程数 

    private finalstatic 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; 

    } 

     

    /**

     * <b>function:</b> 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; 

    } 

} 

package com.hoo.entity;/*** <b>function:</b> 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 hoojo_@126.com* @version 1.0*/ public class DownloadInfo {//下载文件urlprivate 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;}/*** <b>function:</b> 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;}@Overridepublic String toString() {return this.url + "#" + this.fileName + "#" + this.filePath + "#" + this.splitter;} }

 

二、随机写入一段文件

[java] view plaincopyprint?

package com.hoo.download; 

 

import java.io.IOException; 

import java.io.RandomAccessFile; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @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); 

    } 

     

    /**

     * <b>function:</b> 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 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> 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 hoojo_@126.com* @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);}/*** <b>function:</b> 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

[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; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @version 1.0

*/ 

public class DownloadFileextends 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 staticfinal 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; 

        } 

    } 

     

    /**

     * <b>function:</b> 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 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; 

            } 

        } 

    } 

     

    /**

     * <b>function:</b> 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 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> 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 hoojo_@126.com* @version 1.0*/ public class DownloadFile extends Thread {//下载文件urlprivate 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idprivate 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);}@Overridepublic 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10000msconn.setConnectTimeout(10000);// 设置读取数据超时时间为10000msconn.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;}}/*** <b>function:</b> 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;}}}/*** <b>function:</b> 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

[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; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @version 1.0

*/ 

public class BatchDownloadFileimplements 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 staticfinal 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 = newlong[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(); 

    } 

     

    /**

     * <b>function:</b>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(); 

    } 

     

    /**

     * <b>function:</b> 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; 

    } 

} 

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 hoojo_@126.com* @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()];}}@Overridepublic 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();}/*** <b>function:</b>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();}/*** <b>function:</b> 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 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 {//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

[java] view plaincopyprint?

package com.hoo.util; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @version 1.0

*/ 

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 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);} }

下载工具类

[java] view plaincopyprint?

package com.hoo.util; 

 

import com.hoo.download.BatchDownloadFile; 

import com.hoo.entity.DownloadInfo; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @version 1.0

*/ 

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 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();} }

下载测试类

[java] view plaincopyprint?

package com.hoo.test; 

 

import com.hoo.util.DownloadUtils; 

 

/**

* <b>function:</b> 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 hoojo_@126.com

* @version 1.0

*/ 

public class TestDownloadMain { 

 

    public staticvoid 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); 

    } 

} 

package com.hoo.test;import com.hoo.util.DownloadUtils;/*** <b>function:</b> 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 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。

本文转载于：http://blog.csdn.net/ibm_hoojo/article/details/6838222

转载于:https://www.cnblogs.com/ouyangpeng/archive/2013/04/04/8538416.html

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