Java實現多線程下載 URL以及URLConnection

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 主線程：public class MultiThreadDown {public static void main(String[] args) throws Exception{//初始化Downutil對象    final DownUtil downutil = new DownUtil("http://www.crazyit.org/"+"attachment.PHP?aid=MTY0NXxjNjBIYznjN3wxMzE1NTQ2MjU5fGNho"+"D1KVmpXVmhpNG1kWmVzR2JZbnluZWpqs11Od3JzckdodXJOMUpOWWt0aTJz,", "oracelsql.rar", 4);//開始下載downutil.download();new Thread(){public void run(){while(downutil.getCompleteRate() < 1){//每隔0.1秒查詢一次任務完成的進度//GUI程式中可根據進度來繪製進度條System.out.println("已完成：" + downutil.getCompleteRate());try {Thread.sleep(100);} catch (Exception e) {// TODO: handle exceptione.printStackTrace();}}}}.start();}}package nettest;import Java.io.InputStream;import java.io.RandomAccessFile;import java.NET.HttpURLConnection;import java.Net.URL;public class DownUtil {//定義下載資源的路徑private String path;//指定所下載檔案的儲存位置private String targetFile;//定義需要使用多少個線程下載資源private int threadNum;//定義下載的線程對象private DownThread[] threads;//定義下載的檔案的大小private int fileSize;public DownUtil(String path,String targetFile,int threadNum){this.path = path;this.targetFile = targetFile;this.threadNum = threadNum;threads = new DownThread[threadNum]; }public void download() throws Exception{URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setConnectTimeout(5*1000);conn.setRequestMethod("GET");conn.addRequestProperty("Accept", "image/gif,image/jpeg,image/pjpeg,image/pjpeg,"+"application/x-shockwave-flash,application/xaml + xml,"+"application/vnd.ms-xpsdocument,application/x-ms-xbap,"+"application/x-ms-application,application/vnd.ms-excel,"+"application/vnd.ms-powerpoint,application/msword,*/*");conn.setRequestProperty("Accept-Language", "zh-CN");conn.setRequestProperty("Charset", "UTF-8");conn.setRequestProperty("Connection", "Keep-Alive");fileSize = conn.getContentLength();conn.disconnect();int currentPartSize = fileSize/threadNum + 1;RandomAccessFile file = new RandomAccessFile(targetFile, "rw");//得到設定本地檔案的大小file.setLength(fileSize);file.close();for (int i = 0; i < threadNum; i++) {//計算每個線程下載的開始位置int startPos = i*currentPartSize;//每個線程使用一個RandomAccessFile進行下載RandomAccessFile currentPart = new RandomAccessFile(targetFile, "rw");currentPart.seek(startPos);//建立下載線程threads[i] = new DownThread(startPos, currentPartSize, currentPart);//啟動下載線程threads[i].start();}}//獲得下載完成的百分比public double getCompleteRate(){//統計多個線程已經下載的總大小int sumSize = 0;for (int i = 0; i < threadNum; i++) {sumSize += threads[i].length;}//返回已經完成的百分比return sumSize*1.0/fileSize;}private class DownThread extends Thread{//當前線程的下載位置private int startPos;//定義當前線程負責下載的檔案大小private int currentPartSize;//當前線程需要下載的檔案塊private RandomAccessFile currentPart;//定義該線程已經下載的位元組數public int length;public DownThread(int startPos,int currentPartSize,RandomAccessFile currentPart){this.startPos = startPos;this.currentPartSize = currentPartSize;this.currentPart = currentPart;}public void run(){try{URL url = new URL(path);HttpURLConnection conn = (HttpURLConnection) url.openConnection();conn.setConnectTimeout(5*1000);conn.setRequestMethod("GET");conn.addRequestProperty("Accept", "image/gif,image/jpeg,image/pjpeg,image/pjpeg,"+"application/x-shockwave-flash,application/xaml + xml,"+"application/vnd.ms-xpsdocument,application/x-ms-xbap,"+"application/x-ms-application,application/vnd.ms-excel,"+"application/vnd.ms-powerpoint,application/msword,*/*");conn.setRequestProperty("Accept-Language", "zh-CN");conn.setRequestProperty("Charset", "UTF-8");InputStream inStream = conn.getInputStream();//跳過startPos個位元組，表明該線程只下載自己負責的那部分檔案inStream.skip(this.startPos);byte[] buffer = new byte[1024];int hasRead = 0;while(length < currentPartSize && (hasRead = inStream.read(buffer)) != -1){currentPart.write(buffer, 0, hasRead);//累計該線程的下載大小length += hasRead;}currentPart.close();inStream.close();}catch (Exception e){e.printStackTrace();}}}}

 

Java實現多線程下載 URL以及URLConnection