Vamos supor que o teu plugin poderá utilizar Sql numas coisas e MongoDb noutras, isto vai resolver o teu problema de uma maneira correta.

DatabaseMetaBuilder.java

import java.util.Properties;
import java.util.function.Consumer;

public interface DatabaseMetaBuilder {

    DatabaseMetaBuilder with(Consumer<DatabaseMetaBuilder> consumer);

    void addProperty(String key, String value);
  
    Properties wrap();

    class Impl implements DatabaseMetaBuilder {
        private Properties connectionProps;

        public Impl() {
            connectionProps = new Properties();
        }

        @Override
        public DatabaseMetaBuilder with(Consumer<DatabaseMetaBuilder> consumer) {
            consumer.accept(this);
            return this;
        }

        @Override
        public void addProperty(String key, String value) {
            connectionProps.setProperty(key, value);
        }

        @Override
        public Properties wrap() {
            return connectionProps;
        }
    }
}

DatabaseProvider.java

import java.util.function.Consumer;

public interface DatabaseProvider {

    void connect();

    void close();
    
}

ExamplePlugin.java

import eu.unionmc.nations.database.DatabaseProvider;
import eu.unionmc.nations.database.SqlProvider;
import eu.unionmc.nations.database.DatabaseMetaBuilder;
import org.bukkit.plugin.java.JavaPlugin;

public class Main extends JavaPlugin {

    private DatabaseProvider databaseProvider;

    @Override
    public void onLoad() {
        DatabaseMetaBuilder metaBuilder = new DatabaseMetaBuilder.Impl().with(
                $ -> {
                    $.addProperty("hostname", "localhost");
                    $.addProperty("username", "root");
                    $.addProperty("password", "123");
                    $.addProperty("port", SqlProvider.DEFAULT_PORT);
                }
        );

        databaseProvider = new SqlProvider(metaBuilder.wrap());
    }

    @Override
    public void onEnable() {
        databaseProvider.connect();
    }

    @Override
    public void onDisable() {
        databaseProvider.close();
    }
}

SqlProvider.java

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
import java.util.function.Consumer;

public class SqlProvider implements DatabaseProvider {

    public static final String DEFAULT_PORT = "3306";
    private final String DEFAULT_DBMS = "mysql";

    private Connection connection;
    private Properties connectionProps;

    public SqlProvider(Properties connectionProps) {
        connection = null;
        this.connectionProps = connectionProps;
    }

    @Override
    public void connect() {
        String hostname = connectionProps.getProperty("hostname");
        String portNumber = connectionProps.getProperty("port");

        if(hostname.isEmpty() || portNumber.isEmpty()){
            throw new IllegalArgumentException("Hostname or port are invalid");
        }

        try {
            connection = DriverManager.getConnection(
                    "jdbc:" + DEFAULT_DBMS + "://" +
                            hostname +
                            ":" + portNumber + "/",
                    connectionProps);
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void close() {
        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}