AsyncSqlWorker.java

import net.md_5.bungee.api.ProxyServer;
import net.md_5.bungee.api.plugin.Plugin;
import net.md_5.bungee.api.scheduler.TaskScheduler;

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

public class AsyncSQLWorker {
    private Connection connection;
    private final Plugin owner;
    private final String host, username, password, database;
    private static final TaskScheduler scheduler = ProxyServer.getInstance().getScheduler();

    public AsyncSQLWorker(final Plugin owner,
                          final String host,
                          final String username,
                          final String password,
                          final String database) {
        this.host = host;
        this.username = username;
        this.password = password;
        this.database = database;
        this.owner = owner;
    }
    public void connect(final Consumer<Connection> onConnect) {
        scheduler.runAsync(owner, () -> {
            try {
                connection = DriverManager.getConnection("jdbc:mysql://" + host + "/" + database, username, password);
                onConnect.accept(connection);
            } catch (SQLException throwables) {
                throwables.printStackTrace();
            }
        });
    }
    public void executeAsync(final Consumer<Connection> task) {
        scheduler.runAsync(owner, () ->
                task.accept(connection)
        );
    }
    public void closeConnection() {
        scheduler.runAsync(owner, () -> {
            if(null != connection) {
                try {
                    connection.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        });

    }



}