Java getting download progress

Question

I am writing a Java application (Using NetBeans as an IDE and a jFrame form), and one part of it downloads a file. How can I update a progress bar with the current progress of the download, or at least get the total amount of currently downloaded bytes in another thread?

Below is a part of my code:

Runnable updatethread = new Runnable() {
        public void run() {
            try {
                java.io.BufferedInputStream in = new java.io.BufferedInputStream(new java.net.URL("server/package.zip").openStream());
                java.io.FileOutputStream fos = new java.io.FileOutputStream("package.zip");
                java.io.BufferedOutputStream bout = new BufferedOutputStream(fos,1024);
                byte[] data = new byte[1024];
                int x=0;
                while((x=in.read(data,0,1024))>=0)
                {
                    bout.write(data,0,x);
                }
                bout.close();
                in.close();
            }
            catch(FileNotFoundException e) { } catch (IOException e) { }
        }
    };
new Thread(updatethread).

start();
try {
    updatethread.wait();

} catch (InterruptedException ex) { }

@deejay31 In general, indent it by four spaces or one tab when you encounter a `{`, un-indent it when you encounter a `}`. — The Guy with The Hat, Mar 08 '14 at 18:23

slartidan · Accepted Answer · 2014-03-08T18:35:51.177

A working example, using your code and displaying the progress in a progress bar could look like this:

import java.io.BufferedOutputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;

import javax.swing.JFrame;
import javax.swing.JProgressBar;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;

public class Progressbar {

    public static void main(String[] args) {

        final JProgressBar jProgressBar = new JProgressBar();
        jProgressBar.setMaximum(100000);
        JFrame frame = new JFrame();
        frame.setContentPane(jProgressBar);
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setSize(300, 70);
        frame.setVisible(true);

        Runnable updatethread = new Runnable() {
            public void run() {
                try {

                    URL url = new URL("http://downloads.sourceforge.net/project/bitcoin/Bitcoin/blockchain/bitcoin_blockchain_170000.zip");
                    HttpURLConnection httpConnection = (HttpURLConnection) (url.openConnection());
                    long completeFileSize = httpConnection.getContentLength();

                    java.io.BufferedInputStream in = new java.io.BufferedInputStream(httpConnection.getInputStream());
                    java.io.FileOutputStream fos = new java.io.FileOutputStream(
                            "package.zip");
                    java.io.BufferedOutputStream bout = new BufferedOutputStream(
                            fos, 1024);
                    byte[] data = new byte[1024];
                    long downloadedFileSize = 0;
                    int x = 0;
                    while ((x = in.read(data, 0, 1024)) >= 0) {
                        downloadedFileSize += x;

                        // calculate progress
                        final int currentProgress = (int) ((((double)downloadedFileSize) / ((double)completeFileSize)) * 100000d);

                        // update progress bar
                        SwingUtilities.invokeLater(new Runnable() {

                            @Override
                            public void run() {
                                jProgressBar.setValue(currentProgress);
                            }
                        });

                        bout.write(data, 0, x);
                    }
                    bout.close();
                    in.close();
                } catch (FileNotFoundException e) {
                } catch (IOException e) {
                }
            }
        };
        new Thread(updatethread).

        start();
    }

}

This shows how to do it - before using it you should think about GUI-Threads, etc.

PS: using an existing library, as mentioned by Jazzepi is probably a better idea - if your project environment allows you to use external libraries. — slartidan, Mar 08 '14 at 18:37

score 3 · Answer 2 · edited May 23 '17 at 11:53

I had a similar problem with doing a progress bar for uploads, but the solution is basically the same; create a new CountingOutputStream that extends FileOutputStream and takes a listener that can listen to the bytes as they're written. You can see the OutputStreamProgress class as an example in the link below.

How to get a progress bar for a file upload with Apache HttpClient 4?

It looks like Apache commons IO already has a class that does something similar. This isn't exactly the same thing. You have to poll the OutputStream to find out where it's at, where-as in the solution I provided with the listener, the callbacks are being updated continuously.

http://commons.apache.org/proper/commons-io/apidocs/org/apache/commons/io/output/CountingOutputStream.html

You can get it through maven, or downloading the jar through their website.

Maven -> http://mvnrepository.com/artifact/commons-io/commons-io

Jar -> http://commons.apache.org/proper/commons-io/download_io.cgi

score 2 · Answer 3 · answered Mar 08 '14 at 18:24

URL url = new URL(urlString);
HttpURLConnection httpConnection = (HttpURLConnection) (url.openConnection());
long fileSize = httpConnection.getContentLength();

Notice that the content-length is provided by the server in Http Header.

API for the function getContentLength() :

int java.net.URLConnection.getContentLength()

Returns the value of the content-length header field.

Returns:

the content length of the resource that this connection's URL references, or -1 if the content length is not known.

Java getting download progress

3 Answers3

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