Problem with URL File download

Question

Hi every one i am facing a problem with URL File read Technique
import java.awt.Color;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
public class JarDownloader
     boolean isSuccess = false;
     public JarDownloader(String url)
          downloadJar(url);          
     public boolean isDownloadingSuccess()
          return isSuccess;
     private File deleteExistingFile(String filename)
          File jarf = new File(filename);
          if(jarf.exists())
               jarf.delete();
          return jarf;
     public static void main(String args[]){
          new JarDownloader("url/filename.extension");
     private void downloadJar(String url)
          try
               URL jarurl = new URL(url);
               URLConnection urlc = jarurl.openConnection();
               urlc.setUseCaches(false);
               urlc.setDefaultUseCaches(false);
               InputStream inst = urlc.getInputStream();
               int totlength = urlc.getContentLength();
               System.out.println("Total length "+totlength);
               // If the size is less than 10 kb that means the linkis wrong
               if(totlength<=10*1024)throw new Exception("Wrong Link");
               JFrame jw =new JFrame("Livehelp-Download");
               JPanel jp =new JPanel();
               jp.setLayout(null);
               JLabel jl = new JLabel("Downloading required file(s)...",JLabel.CENTER);
               jl.setBounds(10,10,200,50);
               jp.add(jl);
               JProgressBar jpbar = new JProgressBar(0,totlength);
               jpbar.setBorderPainted(true);
               jpbar.setStringPainted(true);
               jpbar.setBounds(10,70,200,30);
               jpbar.setBackground(Color.BLUE);
               jp.add(jpbar);
               jw.setContentPane(jp);
               jw.pack();
               jw.setResizable(false);
               jw.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
               jw.setLocationRelativeTo(null);
               jw.setSize(220,150);
               jw.setVisible(true);
               int readlngth=0;
               int position=0;
               byte[] readbytes = new byte[totlength];
               while(totlength-position > 0)
                    readlngth = inst.read(readbytes,position,totlength-position);
                    position+=readlngth;
                    jpbar.setValue(position);
               File jarf = deleteExistingFile(filename);
               jarf.createNewFile();
               //FileWriter fwriter=new FileWriter(jarf,true);
               FileOutputStream fout = new FileOutputStream(jarf,true);
               DataOutputStream dout = new DataOutputStream(fout);
               dout.write(readbytes);
               dout.flush();
               dout.close();
               inst.close();
               jw.setVisible(false);
               jw.dispose();
               isSuccess=true;
          }catch(Exception ex)
               isSuccess=false;
}From the above code i received the total length of the PAGE content (i.e here url is a file) when i tried to find the size of that file it return -1.
please help me

Answer 1

I think the real problem is that you don't check the return value from read (it's probably less than data.length indicating an incomplete read). Isn't there a readFully somewhere?