# Example of setting a user-defined class

This is a very simple example of a class that implements the `org.apache.derby.authentication.UserAuthenticator` interface.

    import org.apache.derby.authentication.UserAuthenticator;
    import java.io.FileInputStream;
    import java.util.Properties;
    import java.sql.SQLException;
    /**
      * A simple example of a specialized Authentication scheme.
      * The system property 'derby.connection.requireAuthentication'
      * must be set to true, and 'derby.authentication.provider' must
      * contain the full class name of the overridden authentication
      * scheme, (that is, the name of this class).
      *
      * @see org.apache.derby.authentication.UserAuthenticator
      */
    public class MyAuthenticationSchemeImpl implements
            UserAuthenticator {
        private static final String USERS_CONFIG_FILE = "myUsers.cfg";
        private static Properties usersConfig;

        // Constructor
        // We get passed some Users properties if the
        // authentication service could not set them as
        // part of the System properties.
        //
        public MyAuthenticationSchemeImpl() {
        }

        /* Static block where we load the users definition from a
           users configuration file. */
        static {
            /* Load users config file as Java properties.
               File must be in the same directory where
               Derby is started.
               Otherwise, full path must be specified. */
            FileInputStream in = null;
            usersConfig = new Properties();
            try {
                in = new FileInputStream(USERS_CONFIG_FILE);
                usersConfig.load(in);
                in.close();
            } catch (java.io.IOException ie) {
                // No Config file. Raise error message
                System.err.println(
                    "WARNING: Error during Users Config file retrieval");
                System.err.println("Exception: " + ie);
            }
        }

        /**
         * Authenticate the passed-in user's credentials.
         * A more complex class could make calls
         * to any external users directory.
         *
         * @param userName               The user's name
         * @param userPassword           The user's password
         * @param databaseName           The database
         * @param info                   Additional jdbc connection info.
         * @exception SQLException on failure
         */
        public boolean authenticateUser(String userName,
                String userPassword,
                String databaseName,
                Properties info)
            throws SQLException {
            /* Specific Authentication scheme logic.
               If user has been authenticated, then simply return.
               If user name and/or password are invalid,
               then raise the appropriate exception.

               This example allows only users defined in the
               users config properties object.

               Check if the passed-in user has been defined for the system.
               We expect to find and match the property corresponding to
               the credentials passed in. */
            if (userName == null)
                // We do not tolerate 'guest' user for now.
                return false;

            /* Check if user exists in our users config (file)
               properties set.
               If we did not find the user in the users config set, then
               try to find if the user is defined as a System property. */
            String actualUserPassword;
            actualUserPassword = usersConfig.getProperty(userName);
            if (actualUserPassword == null)
                actualUserPassword = System.getProperty(userName);
            if (actualUserPassword == null)
                // No such passed-in user found
                return false;
            // Check if the password matches
            if (!actualUserPassword.equals(userPassword))
                return false;
            // Now, check if the user is a valid user of the database
            if (databaseName != null) {
             /* If database users restriction lists are present, then
                check if there is one for this database and if so,
                check if the user is a valid one for that database.
                For this example, the only user we authorize in database
                DarkSide is user 'DarthVader'. This is the only database
                users restriction list we have for this example.
                We authorize any valid (login) user to access the
                OTHER databases in the system.
                Note that database users ACLs could be set in the same
                properties file or a separate one and implemented as you
                wish. */
                if (databaseName.equals("DarkSide")) {
                    // Check if user is a valid one
                    if (!userName.equals("DarthVader"))
                        // This user is not a valid one of the passed-in
                        return false;
                }
            }
            // The user is a valid one in this database
            return true;
        }
    }

Parent topic: Specifying authentication with a user-defined class