断点续传的代码

注意事项：每次写流的时候，记得关掉，否则会出现，写到后面的流使用的文件等东东会出现删不掉的情况，影响用户的体验

publicclassMultidload {

      staticintThreadCount= 3;

      staticintfinishedThread= 0;

      //确定下载地址

      staticStringpath="http://192.168.6.125:8080/TakeColor.exe";

     

      publicstaticvoidmain(String[] args){

      

      //发送get请求，请求这个资源的地址

      try{

          URL url =newURL(path);

         HttpURLConnection conn =(HttpURLConnection) url.openConnection();

         conn.setRequestMethod("GET");

         conn.setConnectTimeout(5000);

         conn.setReadTimeout(5000);

        

        if(conn.getResponseCode()==200){

          //拿到所请求文件的大小

        intlength = conn.getContentLength();

         File file =newFile("TakeColor.exe");

        //生存临时文件

         RandomAccessFile raf =newRandomAccessFile(file,"rwd");

        //设置临时文件的大小

         raf.setLength(length);

         raf.close();

        //计算出每个线程应该下载多少字节

        intsize =length /ThreadCount;

        

        for(inti =0;i<ThreadCount;i++){

          //计算线程开始和结束的下载位置

          intstartIndex = i * size;

          intendIndex = (i + 1) * size - 1;

          //如果是最后一个线程，那么结束的位置写死

          if(i==ThreadCount-1){

               endIndex = length-1;

          }

          System.out.println("线程"+ i +"的下载区间是:"+startIndex +"---"+ endIndex);

          newDownLoadThread(startIndex,endIndex,i).start();

           }

         }

       }catch(Exception e) {

          //TODOAuto-generated catch block

          e.printStackTrace();

     }

   }

}

 

      

 

 classDownLoadThreadextendsThread{

       intstartIndex;

       intendIndex;

       intthreadId;

       publicDownLoadThread(intstartIndex,intendIndex,intthreadId){

            super();

             this.startIndex=startIndex;

          this.endIndex=endIndex;

          this.threadId=threadId;

        }

      

        publicvoidrun() {

          

          //TODOAuto-generated method stub

          //再次发送http请求，下载原文件

              HttpURLConnection conn;

              try{

                   File progressFile =newFile(threadId+".text");

                   //判断进度临时问价是否存在

                   if(progressFile.exists()){

                        FileInputStream fis =newFileInputStream(progressFile);

                        BufferedReader br =newBufferedReader(newInputStreamReader(fis));

                        

                        //从进度临时文件中读取上一次临时文件下载的总进度，然后与原本的开始位置相加，得到新的开始位置

                        startIndex+=Integer.parseInt(br.readLine()) ;

                        fis.close();

                   }

                   

                   URL url =newURL(Multidload.path);

                   conn = (HttpURLConnection) url.openConnection();

                   conn.setRequestMethod("GET");

                   conn.setConnectTimeout(5000);

                   conn.setReadTimeout(5000);

                   //设置本次http请求所请求的数据的区间

                   conn.setRequestProperty("Range","bytes="+startIndex+"-"+endIndex);

                   

                   //请求部分数据，响应码是206

                   if(conn.getResponseCode()==206){

                        //流里此时只有1/3原文件的数据

                       InputStream is = conn.getInputStream();

                        byte[] b=newbyte[1024];

                        intlen =0;

                        inttotal=0;

                        //拿到临时文件的输出流

                         File file =newFile("TakeColor.exe");

                        //生存临时文件

                         RandomAccessFile raf =newRandomAccessFile(file,"rwd");

                        //把文件的写入位置移动至startIndex

                         raf.seek(startIndex);

                        while((len = is.read(b))!=-1){

                              raf.write(b, 0, len);

                              total +=len;

                              System.out.println("线程"+threadId+"下载了"+total);

                             

                             //生成一个专门用来记录下载进度的临时文件

                             

                              RandomAccessFile progressRaf =newRandomAccessFile(progressFile,"rwd");

                             //每次读取流里的数据之后，同步把当前线程的总进度写进临时文件中

                              progressRaf.write((total+"").getBytes());

                              progressRaf.close();

                         }

                        raf.close();

                        

                        Multidload.finishedThread++;

                        synchronized(Multidload.path) {

                             if(Multidload.finishedThread==Multidload.ThreadCount){

                                  for(inti= 0; i < Multidload.ThreadCount;i++) {

                                      File f =newFile(i+ ".text");

                                      f.delete();        

                                  }

                                  Multidload.finishedThread= 0;

                                  

                             }

                             

                        }

                        

                    }

              }catch(IOException e) {

                   //TODOAuto-generated catch block

                   e.printStackTrace();

              }

          

         }

 }