java多線程下載檔案和斷點下載

標籤：ace   一個   let   range   xtend   download   eth   靜態變數   刪除   

import java.io.BufferedReader;import java.io.File;import java.io.FileInputStream;import java.io.FileOutputStream;import java.io.IOException;import java.io.InputStream;import java.io.InputStreamReader;import java.io.RandomAccessFile;import java.net.HttpURLConnection;import java.net.URL;import javax.print.attribute.standard.Finishings;public class MultiDownload {    static int ThreadCount = 3;       //代表3個進程    static int finishedThread = 0;   //記錄檔案下完的數字    //確定    static String path = "http://192.168.13.13:8080/QQPlayer.exe";    public static void main(String[] args) {                //發送get請求，請求這個地址的資源        try {            URL url = new URL(path);            HttpURLConnection conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setConnectTimeout(5000);            conn.setReadTimeout(5000);                        if(conn.getResponseCode() == 200){                //拿到所請求資源檔的長度                int length = conn.getContentLength();                                File file = new File("QQPlayer.exe");                //產生臨時檔案                RandomAccessFile raf = new RandomAccessFile(file, "rwd");                //設定臨時檔案的大小                raf.setLength(length);                raf.close();                //計算出每個線程應該下載多少位元組                int size = length / ThreadCount;                                for (int i = 0; i < ThreadCount; i++) {                    //計算線程下載的開始位置和結束位置                    int startIndex = i * size;                    int endIndex = (i + 1) * size - 1;                    //如果是最後一個線程，那麼結束位置寫死                    if(i == ThreadCount - 1){                        endIndex = length - 1;                    }//                    System.out.println("線程" + i + "的下載區間是：" + startIndex + "---" + endIndex);                    new DownLoadThread(startIndex, endIndex, i).start();                }            }        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }        }class DownLoadThread extends Thread{    int startIndex;    int endIndex;    int threadId;        public DownLoadThread(int startIndex, int endIndex, int threadId) {        super();        this.startIndex = startIndex;        this.endIndex = endIndex;        this.threadId = threadId;    }    @Override    public void run() {        //再次發送http請求，下載原檔案        try {            File progressFile = new File(threadId + ".txt");            //判斷進度臨時檔案是否存在            if(progressFile.exists()){                FileInputStream fis = new FileInputStream(progressFile);                BufferedReader br = new BufferedReader(new InputStreamReader(fis));                //從進度臨時檔案中讀取出上一次下載的總進度，然後與原本的開始位置相加，得到新的開始位置                startIndex += Integer.parseInt(br.readLine());                fis.close();            }            System.out.println("線程" + threadId + "的下載區間是：" + startIndex + "---" + endIndex);            HttpURLConnection conn;            URL url = new URL(MultiDownload.path);            conn = (HttpURLConnection) url.openConnection();            conn.setRequestMethod("GET");            conn.setConnectTimeout(5000);            conn.setReadTimeout(5000);            //設定本次http請求所請求的資料的區間            conn.setRequestProperty("Range", "bytes=" + startIndex + "-" + endIndex);                        //請求部分資料，相應碼是206            if(conn.getResponseCode() == 206){                //流裡此時只有1/3原檔案的資料                InputStream is = conn.getInputStream();                byte[] b = new byte[1024];                int len = 0;                int total = 0;                //拿到臨時檔案的輸出資料流                File file = new File("QQPlayer.exe");                RandomAccessFile raf = new RandomAccessFile(file, "rwd");                //把檔案的寫入位置移動至startIndex                raf.seek(startIndex);                while((len = is.read(b)) != -1){                    //每次讀取流裡資料之後，同步把資料寫入臨時檔案                    raf.write(b, 0, len);                    total += len;//                    System.out.println("線程" + threadId + "下載了" + total);                                        //產生一個專門用來記錄下載進度的臨時檔案                    RandomAccessFile progressRaf = new RandomAccessFile(progressFile, "rwd");                    //每次讀取流裡資料之後，同步把當前線程下載的總進度寫入進度臨時檔案中                    progressRaf.write((total + "").getBytes());                    progressRaf.close();                }                System.out.println("線程" + threadId + "下載完畢-------------------小志參上！");                raf.close();                                //把記錄進程的檔案刪除    必須3個進程全部都下載完成後才可以刪除                MultiDownload.finishedThread++;                synchronized (MultiDownload.path) {  //有安全執行緒問題，靜態變數為唯一的                    if(MultiDownload.finishedThread == MultiDownload.ThreadCount){                        for (int i = 0; i < MultiDownload.ThreadCount; i++) {                            File f = new File(i + ".txt");                            f.delete();                        }                        MultiDownload.finishedThread = 0;                    }                }                            }        } catch (Exception e) {            // TODO Auto-generated catch block            e.printStackTrace();        }    }}

 

java多線程下載檔案和斷點下載