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import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.CookieHandler;
import java.net.CookieManager;
import java.net.CookiePolicy;
import java.net.URL;
import java.net.HttpURLConnection;
import java.util.Base64;

public class test
{
	/*
	 * Prefix used to identify redirects to URS for the purpose of
	 * adding authentication headers. For test, this should be:
	 * https://uat.urs.earthdata.nasa.gov for test
	 */
	static String URS = "https://urs.earthdata.nasa.gov";
 

	/*
	 * Simple test.
	 */
	public static void main( String[] args )
	{
		String resource = "<url of resource>";
 		String username = "<URS user ID>";
		String password = "<URS user password>";
		System.out.println("Accessing resource " + resource);
		try
		{
			/*
			 * Set up a cookie handler to maintain session cookies. A custom
			 * CookiePolicy could be used to limit cookies to just the resource
			 * server and URS.
			 */
			CookieHandler.setDefault(
				new CookieManager(null, CookiePolicy.ACCEPT_ALL));

			/* Retreve a stream for the resource */
			InputStream in = getResource(resource, username, password);
			/* Dump the resource out (not a good idea for binary data) */
			BufferedReader bin = new BufferedReader(
				new InputStreamReader(in));
			String line;
			while( (line = bin.readLine()) != null)
			{
				System.out.println(line);
			}
			bin.close();
	    }
	    catch( Exception t)
	    {
	        System.out.println("ERROR: Failed to retrieve resource");
	        System.out.println(t.getMessage());
	        t.printStackTrace();
	    }
	}
 

	/*
	 * Returns an input stream for a designated resource on a URS
	 * authenticated remote server.
	 *
	 */
	public static InputStream getResource(
		String resource, String username, String password) throws Exception
	{
		int redirects = 0;
		/* Place an upper limit on the number of redirects we will follow */
		while( redirects < 10 )
		{
			++redirects;
	        /*
			 * Configure a connection to the resource server and submit the
			 * request for our resource.
			 */
			URL url = new URL(resource);
			HttpURLConnection connection = (HttpURLConnection) url.openConnection();
			connection.setRequestMethod("GET");
			connection.setInstanceFollowRedirects(false);
			connection.setUseCaches(false);
			connection.setDoInput(true);

			/*
			 * If this is the URS server, add in the authentication header.
			 */
			if( resource.startsWith(URS) )
			{
				connection.setDoOutput(true);
				connection.setRequestProperty(
					"Authorization",
					"Basic " + Base64.getEncoder().encodeToString(
						(username + ":" + password).getBytes()));
			}

			/*
			 * Execute the request and get the response status code.
			 * A return status of 200 means is good - it means that we
			 * have got our resource. We can return the input stream
			 * so it can be read (may want to return additional header
			 * information, such as the mime type or size ).
			 */
			int status = connection.getResponseCode();
			if( status == 200 )
			{
				return connection.getInputStream();
	        }

			/*
			 * Any value other than 302 (a redirect) will need some custom
			 * handling. A 401 from URS means that the credentials
			 * are invalid, while a 403 means that the user has not authorized
			 * the application.
			 */
			if( status != 302 )
			{
				throw new Exception(
					"Invalid response from server - status " + status);
			}

			/*
			 * Get the redirection location and continue. This should really
			 * have a null check, just in case.
			 */
			resource = connection.getHeaderField("Location");
		}

		/*
		 * If we get here, we exceeded our redirect limit. This is most likely
		 * a configuration problem somewhere in the remote server.
		 */
		throw new Exception("Redirection limit exceeded");
	}
}