java – How to check if Referer is empty or not before downloading

I have this two URL

  1. From this website https://wvw1.123movies.net/ I got this URL

  1. and from https://oceanofapk.com/ I got this URL

https://51-75-145-23.xyz/OceanofAPK.com/KSWEB_v3.963_[Pro_Mod_By_Stabiron].apk?md5=8RIbo_gkOkiR7c9XrpVDnQ&expires=1655617658

The first one requires Referer but the second one doesn’t require Referer but will throws 403 error if I added Referer to the request.

Adding this to the first one will work

connection.addRequestProperty(“Referer”, url.toExternalForm());

but to the second one throws 403 forbidden error.

So my question is how can I check if the server requires Referer header request or not and based on that download the file.

Full Code

import androidx.appcompat.app.AppCompatActivity;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.PowerManager;
import android.webkit.CookieManager;
import android.widget.Toast;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.FileOutputStream;
import java.net.HttpURLConnection;
import java.net.URL;


public class Demo extends AppCompatActivity {

ProgressDialog mProgressDialog;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_demo);


    // declare the dialog as a member field of your activity


 // instantiate it within the onCreate method
    mProgressDialog = new ProgressDialog(Demo.this);
    mProgressDialog.setMessage("Downloading...");
    mProgressDialog.setIndeterminate(true);
    mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
    mProgressDialog.setCancelable(true);

 // execute this when the downloader must be fired
    final DownloadTask downloadTask = new DownloadTask(Demo.this);
   

downloadTask.execute("https://s02.eplayvid.net/vids/mars.attacks.1996.720p.brrip.x264.yify.mp4");

    //downloadTask.execute("https://51-75-145-23.xyz/OceanofAPK.com/KSWEB_v3.963_[Pro_Mod_By_Stabiron].apk?md5=8RIbo_gkOkiR7c9XrpVDnQ&expires=1655617658");
    mProgressDialog.setOnCancelListener(new DialogInterface.OnCancelListener() {

        @Override
        public void onCancel(DialogInterface dialog) {
            downloadTask.cancel(true); //cancel the task
        }
    });



}


// usually, subclasses of AsyncTask are declared inside the activity class.
// that way, you can easily modify the UI thread from here
private class DownloadTask extends AsyncTask<String, Integer, String> {

    private Context context;
    private PowerManager.WakeLock mWakeLock;

    public DownloadTask(Context context) {
        this.context = context;
    }

    @Override
    protected String doInBackground(String... sUrl) {
        InputStream input = null;
        OutputStream output = null;
        HttpURLConnection connection = null;
        try {
            URL url = new URL(sUrl[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.addRequestProperty("Referer", url.toExternalForm());
            connection.setInstanceFollowRedirects(false);
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            connection.setRequestProperty("Accept-Encoding", "identity");
            connection.setRequestProperty("User-Agent", "Mozilla/5.0 (Linux; Android 12) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/101.0.4951.61 Mobile Safari/537.36");

            // Get the cookies for the current domain.
            String cookiesString = CookieManager.getInstance().getCookie(url.toString());

            // Only add the cookies if they are not null.
            if (cookiesString != null) {
                // Add the cookies to the header property.
                connection.setRequestProperty("Cookie", cookiesString);
            }
            connection.connect();

            // expect HTTP 200 OK, so we don't mistakenly save error report
            // instead of the file
            if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                return "Server returned HTTP " + connection.getResponseCode()
                        + " " + connection.getResponseMessage();
            }

            // this will be useful to display download percentage
            // might be -1: server did not report the length
            int fileLength = connection.getContentLength();

            // download the file
            input = connection.getInputStream();
            output = new FileOutputStream("/sdcard/mars.attacks.1996.720p.brrip.x264.yify.mp4");
           //output = new FileOutputStream("/sdcard/ksweb.apk");
           
            byte data[] = new byte[4096];
            long total = 0;
            int count;
            while ((count = input.read(data)) != -1) {
                // allow canceling with back button
                if (isCancelled()) {
                    input.close();
                    return null;
                }
                total += count;
                // publishing the progress....
                if (fileLength > 0) // only if total length is known
                    publishProgress((int) (total * 100 / fileLength));
                output.write(data, 0, count);
            }
        } catch (Exception e) {
            return e.toString();
        } finally {
            try {
                if (output != null)
                    output.close();
                if (input != null)
                    input.close();
            } catch (IOException ignored) {
            }

            if (connection != null)
                connection.disconnect();
        }
        return null;
    }


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // take CPU lock to prevent CPU from going off if the user
        // presses the power button during download
        PowerManager pm = (PowerManager) Demo.this.getSystemService(Context.POWER_SERVICE);
        mWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,
                getClass().getName());
        mWakeLock.acquire();
        mProgressDialog.show();
    }

    @Override
    protected void onProgressUpdate(Integer... progress) {
        super.onProgressUpdate(progress);
        // if we get here, length is known, now set indeterminate to false
        mProgressDialog.setIndeterminate(false);
        mProgressDialog.setMax(100);
        mProgressDialog.setProgress(progress[0]);
    }

    @Override
    protected void onPostExecute(String result) {
        mWakeLock.release();
        mProgressDialog.dismiss();
        if (result != null) {
            Toast.makeText(context, "Download error: " + result, Toast.LENGTH_LONG).show();
            System.out.println(result);
        }else {
            Toast.makeText(context, "File downloaded", Toast.LENGTH_SHORT).show();

        }
    }

}

}

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