package com.coding.week3.download;
import com.coding.week3.download.api.Connection;
import com.coding.week3.download.api.ConnectionException;
import com.coding.week3.download.api.ConnectionManager;
import com.coding.week3.download.api.DownloadListener;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.util.concurrent.atomic.AtomicInteger;
public class FileDownloader {
String url;
DownloadListener listener;
ConnectionManager cm;
String savePath;
int nThread;
int fileLength;
AtomicInteger downloadBytesCount;
public FileDownloader(String _url) {
this.url = _url;
}
public FileDownloader(int nThread, String savePath, String url) {
this.nThread = nThread;
this.savePath = savePath;
this.url = url;
downloadBytesCount = new AtomicInteger(0);
}
public void execute() throws IOException {
// 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。
Connection conn = null;
try {
//根据文件长度为每个线程分配下载字节数量
conn = cm.open(this.url);
fileLength = conn.getContentLength();
//已读字节数量
int perLenOfThread ;
int lastLen ;
Thread[] threads = new Thread[nThread];
if ( fileLength % nThread == 0) {
perLenOfThread = fileLength / nThread;
} else {
lastLen = fileLength % nThread;
perLenOfThread = (fileLength + (nThread - lastLen)) / nThread;
}
//启动线程
for (int i = 0; i < nThread; i++) {
Connection conn1 = cm.open(this.url);
RandomAccessFile ras = new RandomAccessFile(savePath, "rw");
if ( i < nThread - 1) {
threads[i] = new DownloadThread(conn1, perLenOfThread * i, perLenOfThread * (i + 1)-1, ras, downloadBytesCount);
threads[i].start();
} else {
threads[i] = new DownloadThread(conn1, perLenOfThread * (nThread - 1), fileLength - 1, ras, downloadBytesCount);
threads[i].start();
}
}
shutdown(threads);
} catch (ConnectionException e) {
e.printStackTrace();
} finally{
if(conn != null){
conn.close();
}
}
}
private void shutdown(Thread[] threads){
while (true) {
boolean allTerminated = true;
for (int i = 0; i < nThread; i++) {
allTerminated = allTerminated & threads[i].getState().equals(Thread.State.TERMINATED);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
// System.out.println(threads[i].getName() + "状态:"+threads[i].getState().toString());
}
System.out.println("已下载:"+(downloadBytesCount.get()/1024)+"K,百分比:"+ (downloadBytesCount.get()/ (fileLength/100))+"%" );
if (allTerminated) {
listener.notifyFinished();
break;
}
}
}
public void setListener(DownloadListener listener) {
this.listener = listener;
}
public void setConnectionManager(ConnectionManager ucm){
this.cm = ucm;
}
public DownloadListener getListener(){
return this.listener;
}
}