Can't download file from internet using java

Question

I'm trying to download file from internet using java but there have a problem. I'm not failed but each time when I'm trying to download it's downloading only 250-300 KB only though the file size is larger than that. I have tried a lot of ways but every time the result is same.

I have tried Apache Commons IO like this,

import java.io.File;
import java.net.URL;

import org.apache.commons.io.FileUtils;

public class Main {

    public static void main(String[] args) {

        try {

            String from = "https://download.gimp.org/mirror/pub/gimp/v2.8/gimp-2.8.10.tar.bz2";
            String to = "/home/ashik/gimp-2.8.10.tar.bz2";
            System.out.println("Starting!");
            FileUtils.copyURLToFile(new URL(from), new File(to), Integer.MAX_VALUE, Integer.MAX_VALUE);
            System.out.println("Finished!");
        } catch (Exception e) {

            System.err.println(e.toString());
        }
    }
}

I have tried Java NIO like this,

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

public class Main {

    public static void main(String[] args) {

        try {

            String from = "https://download.gimp.org/mirror/pub/gimp/v2.8/gimp-2.8.10.tar.bz2";
            String to = "/home/ashik/gimp-2.8.10.tar.bz2";
            System.out.println("Starting!");
            ReadableByteChannel rbc = Channels.newChannel(new URL(from).openStream());
            FileOutputStream fos = new FileOutputStream(to);
            fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
            fos.close();
            rbc.close();
            System.out.println("Finished!");
        } catch (Exception e) {

            System.err.println(e.toString());
        }
    }

}

I have also followed some stackoverflow solutions like, How to download and save a file from Internet using Java? , How to download large sized Files (size > 50MB) in java, etc but none of them are working.

Every time it's downloading but file size is only 250-300 KB. How to solve this problem?

Platform:

OS: Debian-9

JDK-Version: Oracle JDK-9

IDE: Eclipse Oxygen

Thank you in advance.

Answer 1

You don’t need a third-party library to do this. You could use Channels, but it’s shorter to use Files.copy:

try (InputStream stream = new URL(from).openStream()) {
    Files.copy(stream, Paths.get(to));
}

In your case, the URL is redirecting to a different location. Ordinarily, calling setInstanceFollowRedirects would be sufficient:

HttpURLConnection conn = new URL(from).openConnection();
conn.setInstanceFollowRedirects(true);

try (InputStream stream = conn.getInputStream()) {
    Files.copy(stream, Paths.get(to));
}

However, this is a special case. Your URL is an https URL, which redirects to an http URL.

Java considers that insecure (as it should), so it will never automatically follow that redirect, even if setInstanceFollowRedirects has been called.

Which means you have to follow the redirects yourself:

URL url = new URL(from);

HttpURLConnection conn;
while (true) {
    conn = (HttpURLConnection) url.openConnection();
    conn.setInstanceFollowRedirects(true);

    int responseCode = conn.getResponseCode();
    if (responseCode != HttpURLConnection.HTTP_MOVED_PERM &&
        responseCode != HttpURLConnection.HTTP_MOVED_TEMP &&
        responseCode != 307) {

        break;
    }

    url = new URL(conn.getHeaderField("Location"));
}

try (InputStream stream = conn.getInputStream()) {
    Files.copy(stream, Paths.get(to));
}