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luoziyihaoluoziyihao
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Merge pull request onlyliuxin#47 from 240094626/master
work0315-240094626
2 parents 82f411c + a9c2dd5 commit 92d1e44

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‎group17/240094626/work_0305/src/com/coderising/download/DownloadThread.java

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package com.coderising.download;
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import java.io.RandomAccessFile;
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import java.util.concurrent.CyclicBarrier;
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import com.coderising.download.api.Connection;
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public class DownloadThread extends Thread{
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private Connection conn;
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private int startPos;
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private int endPos;
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private int threadId;
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private String localFile;
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private static final int BUFF_LENGTH = 1024 * 4;
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boolean isFinished = false;
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int currSize = 0;
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CyclicBarrier barrier;
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public DownloadThread( Connection conn, int startPos, int endPos,int threadId,String localFile,CyclicBarrier barrier){
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this.conn = conn;
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this.startPos = startPos;
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this.endPos = endPos;
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this.threadId = threadId;
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this.localFile = localFile;
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this.barrier = barrier;
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}
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public void run(){
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try {
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System.out.println("Thread"+threadId+" begin download bytes range:"+startPos+"-"+endPos);
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RandomAccessFile raf = new RandomAccessFile(localFile, "rw");
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int totalLen = endPos - startPos + 1;
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while(currSize < totalLen){
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int start = currSize + startPos;
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int end = start + BUFF_LENGTH-1;
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byte[] data = conn.read(start,(end>endPos?endPos:end));
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raf.seek(start);
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raf.write(data);
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currSize += data.length;
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}
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raf.close();
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barrier.await(); //等待别的线程完成
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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}

‎group17/240094626/work_0305/src/com/coderising/download/FileDownloader.java

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package com.coderising.download;
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import java.io.IOException;
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import java.io.RandomAccessFile;
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import java.util.concurrent.CyclicBarrier;
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import com.coderising.download.api.Connection;
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import com.coderising.download.api.ConnectionManager;
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import com.coderising.download.api.DownloadListener;
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public class FileDownloader {
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private String url;
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private DownloadListener listener;
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private ConnectionManager cm;
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private String localFile;
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private int threadNum;
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//一组开始下载位置
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private int[] startPos;
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//一组结束下载位置
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private int[] endPos;
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public FileDownloader(String _url,int threadNum,String localFile) {
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this.url = _url;
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this.threadNum = threadNum;
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this.localFile = localFile;
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startPos = new int[threadNum];
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endPos = new int[threadNum];
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}
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public void execute(){
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// 在这里实现你的代码， 注意： 需要用多线程实现下载
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// 这个类依赖于其他几个接口, 你需要写这几个接口的实现代码
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// (1) ConnectionManager , 可以打开一个连接，通过Connection可以读取其中的一段（用startPos, endPos来指定）
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// (2) DownloadListener, 由于是多线程下载， 调用这个类的客户端不知道什么时候结束，所以你需要实现当所有
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// 线程都执行完以后， 调用listener的notifiedFinished方法， 这样客户端就能收到通知。
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// 具体的实现思路：
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// 1. 需要调用ConnectionManager的open方法打开连接， 然后通过Connection.getContentLength方法获得文件的长度
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// 2. 至少启动3个线程下载， 注意每个线程需要先调用ConnectionManager的open方法
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// 然后调用read方法， read方法中有读取文件的开始位置和结束位置的参数， 返回值是byte[]数组
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// 3. 把byte数组写入到文件中
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// 4. 所有的线程都下载完成以后， 需要调用listener的notifiedFinished方法
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// 下面的代码是示例代码， 也就是说只有一个线程， 你需要改造成多线程的。
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CyclicBarrier barrier = new CyclicBarrier(threadNum, new Runnable() {
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@Override
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public void run() {
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listener.notifyFinished();
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}
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});
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Connection conn = null;
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try {
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conn = cm.open(this.url);
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int length = conn.getContentLength();
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if(length > 0){
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holderFile(localFile,length);
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for(int i = 0 , len = length/threadNum; i < threadNum; i++){
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int size = i * len;
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startPos[i] = size;
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if(i == threadNum-1){
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endPos[i] = length - 1;
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}else{
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endPos[i] = size + len-1;
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}
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new DownloadThread(cm.open(url),
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startPos[i],
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endPos[i],
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i+1,
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localFile,
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barrier).start();
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}
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}
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} catch (Exception e) {
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e.printStackTrace();
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}finally{
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if(conn != null){
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conn.close();
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}
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}
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}
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private void holderFile(String localFile, int length) throws IOException {
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RandomAccessFile raf = new RandomAccessFile(localFile, "rw");
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for(int i = 0; i < length; i++){
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raf.write(0);
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}
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raf.close();
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}
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public void setListener(DownloadListener listener) {
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this.listener = listener;
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}
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public void setConnectionManager(ConnectionManager ucm){
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this.cm = ucm;
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}
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public DownloadListener getListener(){
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return this.listener;
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}
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}

‎group17/240094626/work_0305/src/com/coderising/download/FileDownloaderTest.java

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package com.coderising.download;
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import org.junit.After;
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import org.junit.Before;
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import org.junit.Test;
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import com.coderising.download.api.ConnectionManager;
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import com.coderising.download.api.DownloadListener;
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import com.coderising.download.impl.ConnectionManagerImpl;
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public class FileDownloaderTest {
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boolean downloadFinished = false;
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@Before
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public void setUp() throws Exception {
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}
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@After
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public void tearDown() throws Exception {
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}
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@Test
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public void testDownload() {
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String url = "http://images2015.cnblogs.com/blog/610238/201604/610238-20160421154632101-286208268.png";
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String localFile = "E:\\Users\\2017coding\\temp\\pic.png";
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int threadNum = Runtime.getRuntime().availableProcessors();
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FileDownloader downloader = new FileDownloader(url,threadNum,localFile);
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ConnectionManager cm = new ConnectionManagerImpl();
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downloader.setConnectionManager(cm);
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downloader.setListener(new DownloadListener() {
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@Override
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public void notifyFinished() {
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downloadFinished = true;
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}
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});
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downloader.execute();
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// 等待多线程下载程序执行完毕
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while (!downloadFinished) {
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try {
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System.out.println("还没有下载完成，休眠五秒");
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//休眠5秒
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Thread.sleep(5000);
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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System.out.println("下载完成！");
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}
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}

‎group17/240094626/work_0305/src/com/coderising/download/api/Connection.java

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package com.coderising.download.api;
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import java.io.IOException;
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public interface Connection {
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/**
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* 给定开始和结束位置， 读取数据， 返回值是字节数组
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* @param startPos 开始位置， 从0开始
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* @param endPos 结束位置
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* @return
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* @throws Exception
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*/
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public byte[] read(int startPos,int endPos) throws Exception;
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/**
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* 得到数据内容的长度
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* @return
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*/
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public int getContentLength();
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/**
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* 关闭连接
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*/
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public void close();
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}

‎group17/240094626/work_0305/src/com/coderising/download/api/ConnectionException.java

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package com.coderising.download.api;
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import java.io.PrintStream;
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import java.io.PrintWriter;
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import java.io.StringWriter;
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public class ConnectionException extends Exception {
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private static final long serialVersionUID = 5581807994119179835L;
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private String message;
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private Throwable t;
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private String stackTrace;
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public Throwable getCause(){
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return this.t;
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}
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public String toString(){
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return this.message;
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}
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public void printStackTrace() {
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System.err.print(this.stackTrace);
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}
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public void printStackTrace(PrintStream paramPrintStream) {
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printStackTrace(new PrintWriter(paramPrintStream));
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}
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public void printStackTrace(PrintWriter paramPrintWriter) {
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paramPrintWriter.print(this.stackTrace);
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}
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public ConnectionException(String paramString) {
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super(paramString);
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this.message = paramString;
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this.stackTrace = paramString;
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}
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public ConnectionException(Throwable paramThrowable) {
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super(paramThrowable.getMessage());
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this.t = paramThrowable;
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StringWriter localStringWriter = new StringWriter();
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paramThrowable.printStackTrace(new PrintWriter(localStringWriter));
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this.stackTrace = localStringWriter.toString();
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}
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public ConnectionException(String paramString, Throwable paramThrowable) {
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super(paramString + "; nested exception is "
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+ paramThrowable.getMessage());
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this.t = paramThrowable;
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this.message = paramString;
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StringWriter localStringWriter = new StringWriter();
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paramThrowable.printStackTrace(new PrintWriter(localStringWriter));
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this.stackTrace = localStringWriter.toString();
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}
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}

‎group17/240094626/work_0305/src/com/coderising/download/api/ConnectionManager.java

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package com.coderising.download.api;
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public interface ConnectionManager {
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/**
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* 给定一个url , 打开一个连接
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* @param url
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* @return
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*/
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public Connection open(String url) throws ConnectionException;
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}

‎group17/240094626/work_0305/src/com/coderising/download/api/DownloadListener.java

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package com.coderising.download.api;
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public interface DownloadListener {
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public void notifyFinished();
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}

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