Connection Pool Tutorial example

    @Override
    public boolean onCommand(final CommandSender sender, Command cmd, String label, String[] args) {
        if (cmd.getName().equalsIgnoreCase("testupdate")) {
            if (args.length == 0) {
                sender.sendMessage("Starting an asynchronous task.");

                new BukkitRunnable() {
                    @Override
                    public void run() {
                        sender.sendMessage("Asynchronous task started.");
                        sender.sendMessage("Starting database transacation.");
                        Connection connection = null;
                        PreparedStatement preparedStatement = null;

                        try {
                            connection = dataSource.getConnection();
                            preparedStatement = connection.prepareStatement("INSERT INTO Test (Key, Value) VALUES ('0', '10')");
                            int rows = preparedStatement.executeUpdate();
                            sender.sendMessage("Transaction succeeded. Inserted: " + rows);
                            // WARNING! If you want to call not thread-safe API methods here, put it into a synchronous task!
                        } catch (SQLException e) {
                            sender.sendMessage("Transaction failed.");
                        } finally {
                            sender.sendMessage("Closing resources.");

                            if (preparedStatement != null) {
                                try {
                                    preparedStatement.close();
                                } catch (SQLException e) {
                                    sender.sendMessage("Error while closing statement.");
                                }
                            }

                            if (connection != null) {
                                try {
                                    connection.close();
                                } catch (SQLException e) {
                                    sender.sendMessage("Error while closing connection.");
                                }
                            }
                        }
                    }
                }.runTaskAsynchronously(this);
            }
        } else if (cmd.getName().equalsIgnoreCase("testquery")) {
            if (args.length == 0) {
                sender.sendMessage("Starting an asynchronous task.");

                new BukkitRunnable() {
                    @Override
                    public void run() {
                        sender.sendMessage("Asynchronous task started.");
                        sender.sendMessage("Starting database transaction.");
                        Connection connection = null;
                        PreparedStatement preparedStatement = null;
                        ResultSet resultSet = null;

                        try {
                            connection = dataSource.getConnection();
                            preparedStatement = connection.prepareStatement("SELECT * FROM Test WHERE Key = '0'");
                            resultSet = preparedStatement.executeQuery();

                            if (resultSet.next()) {
                                sender.sendMessage("Transaction succeeded. Value: " + resultSet.getInt("Value"));
                                // WARNING! If you want to call not thread-safe API methods here, put it into a synchronous task!
                            } else {
                                sender.sendMessage("Transaction succeeded. No value.");
                            }
                        } catch (SQLException e) {
                            sender.sendMessage("Transaction failed.");
                        } finally {
                            sender.sendMessage("Closing resources.");

                            if (resultSet != null) {
                                try {
                                    resultSet.close();
                                } catch (SQLException e) {
                                    sender.sendMessage("Error while closing result set.");
                                }
                            }

                            if (preparedStatement != null) {
                                try {
                                    preparedStatement.close();
                                } catch (SQLException e) {
                                    sender.sendMessage("Error while closing statement.");
                                }
                            }

                            if (connection != null) {
                                try {
                                    connection.close();
                                } catch (SQLException e) {
                                    sender.sendMessage("Error while closing connection.");
                                }
                            }
                        }
                    }
                }.runTaskAsynchronously(this);
            }
        }

        return false;
    }