Merge pull request onlyliuxin#38 from wjwzero/master

多线程下载

group26/723161901/src/com/download/download/DownloadThread.java

@@ -0,0 +1,39 @@
+package com;
+
+import java.io.RandomAccessFile;
+import java.util.concurrent.CyclicBarrier;
+
+import com.api.Connection;
+
+public class DownloadThread extends Thread{
+
+	private Connection conn;
+	private int startPos;
+	private int endPos;
+	private String localFile;
+	private CyclicBarrier barrier;
+
+	public DownloadThread( Connection conn, int startPos, int endPos, String localFile, CyclicBarrier barrier){
+		this.conn = conn;		
+		this.startPos = startPos;
+		this.endPos = endPos;
+		this.localFile = localFile;
+		this.barrier = barrier;
+	}
+
+	public void run(){	
+		try {
+
+			byte[] data =conn.read(startPos, endPos);
+
+			RandomAccessFile file = new RandomAccessFile(localFile,"rw");
+			file.seek(startPos);
+			file.write(data);
+			file.close();
+			conn.close();
+			barrier.await();
+		} catch (Exception e) {
+			e.printStackTrace();
+		}
+	}
+}

group26/723161901/src/com/download/download/FileDownloader.java

@@ -0,0 +1,116 @@
+package com;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.util.concurrent.CyclicBarrier;
+
+import com.api.Connection;
+import com.api.ConnectionException;
+import com.api.ConnectionManager;
+import com.api.DownloadListener;
+
+
+public class FileDownloader {
+
+	private String url;
+	private String localFile;
+
+	DownloadListener listener;
+
+	ConnectionManager cm;
+	private static final int DOWNLOAD_THREAD_NUM = 3;
+
+
+	public FileDownloader(String _url, String localFile) {
+		this.url = _url;
+		this.localFile = localFile;
+	}
+
+	public void execute(){
+		// 在这里实现你的代码， 注意： 需要用多线程实现下载
+		// 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
+		// (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）
+		// (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
+		//     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。
+		// 具体的实现思路：
+		// 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
+		// 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
+		// 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
+		// 3. 把byte数组写入到文件中
+		// 4. 所有的线程都下载完成以后， 需要调用listener的notifiedFinished方法
+
+		// 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。
+
+		CyclicBarrier barrier = new CyclicBarrier(DOWNLOAD_THREAD_NUM, new Runnable(){
+			@Override
+			public void run() {
+				listener.notifyFinished();
+			}
+		});
+		Connection conn = null;
+		try {
+
+			conn = cm.open(this.url);
+
+			int length = conn.getContentLength();	
+			createPlaceHolderFile(this.localFile, length);
+			int[][] ranges = allocateDownloadRange(DOWNLOAD_THREAD_NUM, length);
+			for(int i=0; i<DOWNLOAD_THREAD_NUM; i++){
+				DownloadThread thread = new DownloadThread(cm.open(url), ranges[i][0], ranges[i][1], localFile, barrier);
+				thread.start();
+			}
+
+		} catch (Exception e) {			
+			e.printStackTrace();
+		}finally{
+			if(conn != null){
+				conn.close();
+			}
+		}
+
+
+
+
+	}
+
+	private int[][] allocateDownloadRange(int threadNum, int contentLen) {
+		int[][] ranges = new int[threadNum][2];
+
+		int eachThreadSize = contentLen/threadNum;
+		int left = contentLen % threadNum;
+		for(int i=0; i<threadNum; i++){
+			int startPos = i*eachThreadSize;
+			int endPos = (i+1)*eachThreadSize-1;
+			if((i==(threadNum-1))){
+				endPos += left;
+			}
+			ranges[i][0] = startPos;
+			ranges[i][1] = endPos;
+		}
+		return ranges;
+	}
+
+	private void createPlaceHolderFile(String fileName, int length) throws IOException {
+		RandomAccessFile file = new RandomAccessFile(fileName,"rw");
+		for(int i=0; i<length; i++){
+			file.write(0);
+		}
+		file.close();
+	}
+
+	public void setListener(DownloadListener listener) {
+		this.listener = listener;
+	}
+
+
+
+	public void setConnectionManager(ConnectionManager ucm){
+		this.cm = ucm;
+	}
+
+	public DownloadListener getListener(){
+		return this.listener;
+	}
+
+}

group26/723161901/src/com/download/download/FileDownloaderTest.java

@@ -0,0 +1,59 @@
+package com;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import com.api.ConnectionManager;
+import com.api.DownloadListener;
+import com.impl.ConnectionManagerImpl;
+
+public class FileDownloaderTest {
+	boolean downloadFinished = false;
+	@Before
+	public void setUp() throws Exception {
+	}
+
+	@After
+	public void tearDown() throws Exception {
+	}
+
+	@Test
+	public void testDownload() {
+
+		String url = "http://images2015.cnblogs.com/news/24442/201703/24442-20170331150421570-489464769.jpg";
+
+		FileDownloader downloader = new FileDownloader(url, "/Users/Macx/Workspaces/MyEclipse 2017 CI/download/src/489464769.jpg");
+
+
+		ConnectionManager cm = new ConnectionManagerImpl();
+		downloader.setConnectionManager(cm);
+
+		downloader.setListener(new DownloadListener() {
+			@Override
+			public void notifyFinished() {
+				downloadFinished = true;
+			}
+
+		});
+
+
+		downloader.execute();
+
+		// 等待多线程下载程序执行完毕
+		while (!downloadFinished) {
+			try {
+				System.out.println("还没有下载完成，休眠五秒");
+				//休眠5秒
+				Thread.sleep(5000);
+			} catch (InterruptedException e) {				
+				e.printStackTrace();
+			}
+		}
+		System.out.println("下载完成！");
+
+
+
+	}
+
+}

group26/723161901/src/com/download/download/api/Connection.java

@@ -0,0 +1,23 @@
+package com.api;
+
+import java.io.IOException;
+
+public interface Connection {
+	/**
+	 * 给定开始和结束位置， 读取数据， 返回值是字节数组
+	 * @param startPos 开始位置， 从0开始
+	 * @param endPos 结束位置
+	 * @return
+	 */
+	public byte[] read(int startPos,int endPos) throws IOException;
+	/**
+	 * 得到数据内容的长度
+	 * @return
+	 */
+	public int getContentLength();
+
+	/**
+	 * 关闭连接
+	 */
+	public void close();
+}

group26/723161901/src/com/download/download/api/ConnectionException.java

@@ -0,0 +1,5 @@
+package com.api;
+
+public class ConnectionException extends Exception {
+
+}

group26/723161901/src/com/download/download/api/ConnectionManager.java

@@ -0,0 +1,10 @@
+package com.api;
+
+public interface ConnectionManager {
+	/**
+	 * 给定一个url , 打开一个连接
+	 * @param url
+	 * @return
+	 */
+	public Connection open(String url) throws ConnectionException;	
+}

group26/723161901/src/com/download/download/api/DownloadListener.java

@@ -0,0 +1,5 @@
+package com.api;
+
+public interface DownloadListener {
+	public void notifyFinished();
+}

group26/723161901/src/com/download/download/impl/ConnectionImpl.java

@@ -0,0 +1,69 @@
+package com.impl;
+
+import java.io.ByteArrayOutputStream;
+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 java.util.Arrays;
+
+import com.api.Connection;
+
+public class ConnectionImpl implements Connection{
+
+	private URL url;
+
+
+	public ConnectionImpl(String urlStr) {
+		super();
+		try {
+			this.url = new URL(urlStr);
+		} catch (MalformedURLException e) {
+			e.printStackTrace();
+		}
+	}
+
+	@Override
+	public byte[] read(int startPos, int endPos) throws IOException {
+		HttpURLConnection httpConn = (HttpURLConnection)url.openConnection();
+		httpConn.setRequestProperty("Range", "bytes="+startPos+"-"+endPos);
+		InputStream in = httpConn.getInputStream();
+		byte[] buff = new byte[1024];
+		int totalLen = endPos-startPos+1;
+		ByteArrayOutputStream baos = new ByteArrayOutputStream();
+		while(baos.size() < totalLen){
+			int len = in.read(buff);
+			if(len < 0){
+				break;
+			}
+			baos.write(buff, 0, len);
+		}
+
+		if(baos.size() > totalLen){
+			byte[] data = baos.toByteArray();
+			return Arrays.copyOf(data, totalLen);
+		}
+		return baos.toByteArray();
+	}
+
+	@Override
+	public int getContentLength() {
+		try {
+			URLConnection con = url.openConnection();
+			return con.getContentLength();
+		} catch (IOException e) {
+			// TODO Auto-generated catch block
+			e.printStackTrace();
+		}
+		return -1;
+	}
+
+	@Override
+	public void close() {
+
+
+	}
+
+}

group26/723161901/src/com/download/download/impl/ConnectionManagerImpl.java

@@ -0,0 +1,15 @@
+package com.impl;
+
+import com.api.Connection;
+import com.api.ConnectionException;
+import com.api.ConnectionManager;
+
+public class ConnectionManagerImpl implements ConnectionManager {
+
+	@Override
+	public Connection open(String urlStr) throws ConnectionException {
+
+		return new ConnectionImpl(urlStr);
+	}
+
+}