Java binary file download stops early

Question

I am trying to download an exe file with following code, any idea why it downloads only ~30% of the file? At least it doesn't throw any exceptions.

My main method looks like this: new DownloadWorker().execute();

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;

import javax.swing.SwingWorker;

public final class DownloadWorker extends SwingWorker<Object, Object> {

    @Override
    protected Object doInBackground() throws Exception {
        BufferedInputStream in = null;
        BufferedOutputStream out = null;

        try {
            URL url = new URL("http://download.piriform.com/ccsetup320.exe");
            URLConnection conn = url.openConnection();
            conn.connect();

            int fileLength = conn.getContentLength();

            in = new BufferedInputStream(url.openStream());
            out = new BufferedOutputStream(new FileOutputStream("ccsetup320.exe"));

            byte[] buffer = new byte[4096];
            long total = 0;
            int bytesRead = 0;
            while ( (bytesRead = in.read(buffer)) != -1 ) {
                total += bytesRead;
                System.out.println((int) (total * 100 / fileLength));
                out.write(buffer, 0, bytesRead);
            }
        } catch ( Exception e ) {
            e.printStackTrace();
        } finally {
            if ( out != null ) {
                out.flush();
                out.close();
            }
            if ( in != null ) {
                in.close();
            }
        }

        return null;
    }

    @Override
    protected void done() {

    }

}

Thanks.

Your exact code (cut and paste) works fine for me, giving the same size (3,889,704 bytes) and MD5 sum (9039731b97c63d6759bbcbbbb14db6ab) as downloading in Chrome. — Jon Skeet, Jul 01 '12 at 21:27
I'm using jdk1.7.0_04 and the System.out.println stops between 30 and 36, and the output file is also around 1.3 mb — perak, Jul 01 '12 at 21:31
@perrtuk, your code works fine for me? It goes to 100, and I have the same Java version, why not try using NIO API of java 7, see answer below — David Kroukamp, Jul 01 '12 at 21:47
I just noticed that both codes do work when I execute them directly from the main method, but fail when I use SwingWorker. — perak, Jul 01 '12 at 21:55
I think the problem is using `execute()`, on my worker I call `run()`, if I call `execute()` it doesnt work! — David Kroukamp, Jul 01 '12 at 22:15

score 2 · Accepted Answer · edited Jun 20 '20 at 09:12

Have you tried using Java NIO seen as you have Java 7 installed:

import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;


public class TestApp {

    public static void main(String[] args) {
        try {
            URL url = new URL("http://download.piriform.com/ccsetup320.exe");
            ReadableByteChannel rbc = Channels.newChannel(url.openStream());
            FileOutputStream fos = new FileOutputStream("c:/ccsetup320.exe");
            fos.getChannel().transferFrom(rbc, 0, 1 << 24);
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }

}

The above code is tested and works just fine, I got it from a similar question found here we can see how the NIO makes coding so much easier :)

EDIT:

I have updated the code to use a swingworker and it downloads the file without a problem:

import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import javax.swing.SwingWorker;

public class JavaApplication174 {

    public static void main(String[] args) {
        SwingWorker worker = new SwingWorker() {

            @Override
            protected Object doInBackground() throws Exception {

                try {
                    URL google = new URL("http://download.piriform.com/ccsetup320.exe");
                    ReadableByteChannel rbc = Channels.newChannel(google.openStream());
                    FileOutputStream fos = new FileOutputStream("c:/ccsetup320.exe");
                    fos.getChannel().transferFrom(rbc, 0, 1 << 24);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
                return this;
            }
        };
        worker.run();
    }
}

EDIT 2:

You call execute() on your workers instance use run() instead works for me!

This works when executed directly from main method, but not when it's in SwingWorker, I've updated my question. — perak, Jul 01 '12 at 22:01
@perrtuk I have edited the code to incorporate a `SwingWorker`, and it seems to be working just fine? — David Kroukamp, Jul 01 '12 at 22:09

score 0 · Answer 2 · answered Jul 02 '12 at 10:52

i think your error lies in this loop because the -1 isn't being written (that is the last byte that marks the file end):

        while ( (bytesRead = in.read(buffer)) != -1 ) {
            total += bytesRead;
            System.out.println((int) (total * 100 / fileLength));
            out.write(buffer, 0, bytesRead);
        }

Change it to:

        do {
            bytesRead = in.read(buffer);
            total += bytesRead;
            System.out.println((int) (total * 100 / fileLength));
            out.write(buffer, 0, bytesRead);
        }while(bytesRead!=-1);

Java binary file download stops early

2 Answers2