/*
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     * To change this template file, choose Tools | Templates
     * and open the template in the editor.
     */
    package de.freakyonline.uconeplugin;

    import java.sql.Connection;
    import java.sql.DriverManager;
    import java.sql.PreparedStatement;
    import java.sql.ResultSet;
    import java.sql.SQLException;
    import java.sql.Statement;
    import java.util.Collection;
    import java.util.UUID;
    import static java.util.logging.Level.INFO;
    import java.util.logging.Logger;
    import org.bukkit.Bukkit;
    import org.bukkit.entity.Player;
    import org.bukkit.event.Listener;
    import org.bukkit.event.player.PlayerJoinEvent;
    import org.bukkit.plugin.java.JavaPlugin;
    import org.bukkit.scheduler.BukkitRunnable;

    /**
     *
     * @author uwe
     */
    public class UCOnePlugin extends JavaPlugin {

        private Connection mySQLConnection;
        private String host, database, username, password;
        private int port;
        Statement statement;

        @Override
        public void onEnable() {

            Logger logger = Bukkit.getLogger();

            host = "localhost";
            port = 3306;
            database = "UCOnePlugin";
            username = "UCOnePlugin";
            password = "p9PC967UgQmUPK2t";

            try {
                openMySQLConnection();
            } catch(ClassNotFoundException e) {
                e.printStackTrace();
            } catch(SQLException e) {
                e.printStackTrace();
            }

            logger.log(INFO, "Before Thread ...");
            Thread ucOnePluginServer = new Thread(new UCOnePluginServer());
            ucOnePluginServer.run();
            logger.log(INFO, "After Thread ...");

            getServer().getPluginManager().registerEvents(new UCOnePluginListener(mySQLConnection), this);

        }

        @Override
        public void onDisable() {
            PreparedStatement updateOnDisable = null; // Update last quit on disable
            PreparedStatement qryIfExists = null;
            ResultSet result;

            Collection<?extends Player> onlinePlayerList = Bukkit.getOnlinePlayers();

            for(Player player : onlinePlayerList) {

                String uuid = player.getUniqueId().toString();
                try {
                    qryIfExists = mySQLConnection.prepareStatement("SELECT pid FROM PlayerList WHERE uuid = ?");
                    qryIfExists.setString(1, uuid);
                    result = qryIfExists.executeQuery();

                    if(result.next()) {
                        updateOnDisable = mySQLConnection.prepareStatement("UPDATE PlayerList SET lastquit = NOW() WHERE uuid = ?");
                        updateOnDisable.setString(1,uuid);
                        updateOnDisable.executeUpdate();
                    } else {
    //                  consoleLogger(SEVERE,"User has no row in table. Should have after joining.");
                    }
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }

        public void openMySQLConnection() throws SQLException, ClassNotFoundException {
        if (mySQLConnection != null && !mySQLConnection.isClosed()) {
            return;
        }

        synchronized (this) {
            if (mySQLConnection != null && !mySQLConnection.isClosed()) {
                return;
            }
            Class.forName("com.mysql.jdbc.Driver");
            mySQLConnection = DriverManager.getConnection("jdbc:mysql://" + this.host+ ":" + this.port + "/" + this.database, this.username, this.password);
        }
    }

    }

UCOneListener.java:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package de.freakyonline.uconeplugin;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.UUID;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.PlayerJoinEvent;
import org.bukkit.event.player.PlayerQuitEvent;

/**
 *
 * @author uwe
 */
public class UCOnePluginListener implements Listener
{
    Statement statement;
    Connection mySQLConnection;


    public UCOnePluginListener(Connection mySQLConnection) {
               this.mySQLConnection = mySQLConnection;
    }

     @EventHandler
     public void onPlayerJoin(PlayerJoinEvent event) throws SQLException
     {
        ResultSet result;
        PreparedStatement qryIfExists = null;
        PreparedStatement insertNewOnJoin = null;

        UUID uuid = event.getPlayer().getUniqueId();
        String nickName = event.getPlayer().getName();

        try {
            qryIfExists = mySQLConnection.prepareStatement("SELECT pid FROM PlayerList WHERE uuid = ?");
            qryIfExists.setString(1,uuid.toString());
            result = qryIfExists.executeQuery();

            if(!result.next()) {
                insertNewOnJoin = mySQLConnection.prepareStatement("INSERT INTO PlayerList (nickname, uuid, firstjoined)  VALUES (?,?,CURDATE())");
                insertNewOnJoin.setString(1,nickName);
                insertNewOnJoin.setString(2,uuid.toString());
                insertNewOnJoin.executeUpdate();
            }
         } catch (SQLException e) {
            e.printStackTrace();
        }

    }

    @EventHandler
    public void OnPlayerQuit(PlayerQuitEvent event) {
        PreparedStatement updateOnQuit = null;
        PreparedStatement qryIfExists = null;
        ResultSet result;

        String uuid = event.getPlayer().getUniqueId().toString();

        try {
            qryIfExists = mySQLConnection.prepareStatement("SELECT pid FROM PlayerList WHERE uuid = ?");
            qryIfExists.setString(1, uuid);
            result = qryIfExists.executeQuery();

            if(result.next()) {
                updateOnQuit = mySQLConnection.prepareStatement("UPDATE PlayerList SET lastquit = NOW() WHERE uuid = ?");
                updateOnQuit.setString(1,uuid);
                updateOnQuit.executeUpdate();
            } else {
//                consoleLogger(SEVERE,"User has no row in table. Should have after joining.");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package de.freakyonline.uconeplugin;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;
import static java.util.logging.Level.INFO;
import java.util.logging.Logger;
import org.bukkit.Bukkit;

/**
 *
 * @author uwe
 */

// TODO: Make Singleton
public class UCOnePluginServer implements Runnable {
    ArrayList<ObjectOutputStream> clientsConnected;

    public class ClientHandler implements Runnable {
        ObjectInputStream  in;
        Socket clientSocket;

        public ClientHandler (Socket socket) {
            try {
                clientSocket = socket;
                in = new ObjectInputStream(clientSocket.getInputStream());
            } catch (Exception ex) { ex.printStackTrace(); }
        }

        public void run() {
            Object o1 = null;
            ObjectOutputStream toClient;

            try {
                toClient = new ObjectOutputStream(clientSocket.getOutputStream());
                o1 = in.readObject(); // TODO: Get 2 Objects

                String command = o1.toString().toLowerCase();

                Logger logger = Bukkit.getLogger();

                switch (command) {
                    default:  logger.log(INFO,"Got command.");

                }

                toClient.writeObject("Test");

                // TODO: more server code here.

            } catch (Exception ex) { ex.printStackTrace(); }
        }
    }

    public void run() {
        clientsConnected = new ArrayList<ObjectOutputStream>();

        try {
            ServerSocket serverSock = new ServerSocket(2009);

            while(true) {
                Socket clientSocket = serverSock.accept();
                ObjectOutputStream out = new ObjectOutputStream(clientSocket.getOutputStream());
                clientsConnected.add(out);

                Thread t = new Thread(new ClientHandler(clientSocket));
            }

        } catch(Exception ex) {
            ex.printStackTrace();
        }
    }

}