Sample JavaFX application with MySQL JDBC operation.

Database.java

package io.github.julianjupiter.javafx;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Database
 * @author Julian Jupiter
 *
 */
public class Database {
	
	  private static final Logger logger = Logger.getLogger(Database.class.getName());
		private static final String DB_DRIVER = "com.mysql.cj.jdbc.Driver";
		private static final String DB_CONNECTION = "jdbc:mysql://localhost/javafxsample";
		private static final String DB_USER = "root";
		private static final String DB_PASSWORD = "admin";
		
		private Database() {
			
		}
		
		public static Connection getDBConnection() throws SQLException {
			Connection connection = null;

			try {
				Class.forName(DB_DRIVER);
			} catch (ClassNotFoundException exception) {
				logger.log(Level.SEVERE, exception.getMessage());
			}

			try {
				connection = DriverManager.getConnection(DB_CONNECTION, DB_USER, DB_PASSWORD);
				return connection;
			} catch (SQLException exception) {
				logger.log(Level.SEVERE, exception.getMessage());
			}

			return connection;
		}
		
	}

database.sql

-- 1. Create first this database to your MySQL server:
create database javafxsample;
use javafxsample;
create table if not exists user(
	id int(11) not null auto_increment,
	username varchar(255) not null unique,
	last_name varchar(255) not null,
	first_name varchar(255) not null,
	password varchar(255) not null,
	created_at datetime not null default current_timestamp,
	primary key(id)
); 
-- 2. Add mysql-connector-java-6.0.6.jar to your dependencies.
-- 3. Update database credentials in Database.class.

JApps.java

package io.github.julianjupiter.javafx;

import java.util.logging.Level;
import java.util.logging.Logger;

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.scene.control.Alert.AlertType;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.PasswordField;
import javafx.scene.control.TextField;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.text.Font;
import javafx.scene.text.FontWeight;
import javafx.scene.text.Text;
import javafx.stage.Stage;

public class JApps extends Application {

	private static final Logger logger = Logger.getLogger(JApps.class.getName());
	private UserDao userDao = new UserDao();

	@Override
	public void start(Stage primaryStage) {
		primaryStage.setTitle("JavaFX Welcome");

		GridPane grid = new GridPane();
		grid.setAlignment(Pos.CENTER);
		grid.setHgap(10);
		grid.setVgap(10);
		grid.setPadding(new Insets(25, 25, 25, 25));

		Text scenetitle = new Text("Add User");
		scenetitle.setFont(Font.font("Tahoma", FontWeight.NORMAL, 20));
		grid.add(scenetitle, 0, 0, 2, 1);

		Label userNameLabel = new Label("Username:");
		grid.add(userNameLabel, 0, 1);

		TextField usernameTextField = new TextField();
		grid.add(usernameTextField, 1, 1);

		Label lastNameLabel = new Label("Last Name:");
		grid.add(lastNameLabel, 0, 2);

		TextField lastNameTextField = new TextField();
		grid.add(lastNameTextField, 1, 2);

		Label firstNameLabel = new Label("First Name:");
		grid.add(firstNameLabel, 0, 3);

		TextField firstNameTextField = new TextField();
		grid.add(firstNameTextField, 1, 3);

		Label passwordLabel = new Label("Password:");
		grid.add(passwordLabel, 0, 4);

		PasswordField passwordField = new PasswordField();
		grid.add(passwordField, 1, 4);

		Button saveButton = new Button("Save");
		HBox hBox = new HBox(10);
		hBox.setAlignment(Pos.BOTTOM_RIGHT);
		hBox.getChildren().add(saveButton);
		grid.add(hBox, 1, 5);

		saveButton.setOnAction(actionEvent -> {
			String username = usernameTextField.getText().trim();
			String lastName = lastNameTextField.getText().trim();
			String firstName = firstNameTextField.getText().trim();
			String password = passwordField.getText();
			if (!StringPool.BLANK.equals(username) && !StringPool.BLANK.equals(lastName)
					&& !StringPool.BLANK.equals(firstName) && !StringPool.BLANK.equals(password)) {
				try {
					if (!userDao.userExists(username)) {
						User user = this.createUserObject(username, lastName, firstName, password);
						int userId = userDao.saveUser(user);
						if (userId > 0) {
							this.alert("Save", "Successful!", AlertType.INFORMATION);
						} else {
							this.alert("Error", "Failed!", AlertType.ERROR);
						}
					} else {
						this.alert("Error", "User already exists!", AlertType.ERROR);
					}
				} catch (Exception exception) {
					logger.log(Level.SEVERE, exception.getMessage());
				}
			} else {
				this.alert("Error", "Please complete fields!", AlertType.ERROR);
			}

		});

		Scene scene = new Scene(grid, 300, 275);
		primaryStage.setScene(scene);

		primaryStage.show();
	}

	public void alert(String title, String message, AlertType alertType) {
		Alert alert = new Alert(alertType);
		alert.setTitle(title);
		alert.setHeaderText(null);
		alert.setContentText(message);

		alert.showAndWait();
	}

	public User createUserObject(String username, String lastName, String firstName, String password) {
		User user = new User();
		user.setUsername(username);
		user.setLastName(lastName);
		user.setFirstName(firstName);
		user.setPassword(password);

		return user;
	}

	public static void main(String[] args) {
		launch(args);
	}

}

StringPool.java

package io.github.julianjupiter.javafx;

/**
 * String Pool utility
 * @author Julian Jupiter
 *
 */
public class StringPool {
	public static final String BLANK = "";
	
	private StringPool() {
		
	}
}

User.java

package io.github.julianjupiter.javafx;

import java.io.Serializable;

/**
 * Domain model
 * 
 * @author Julian Jupiter
 *
 */
public class User implements Serializable {

	private static final long serialVersionUID = 3789909326487155148L;
	private int id;
	private String username;
	private String lastName;
	private String firstName;
	private String password;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getUsername() {
		return username;
	}

	public void setUsername(String username) {
		this.username = username;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}

}

UserDao.java

package io.github.julianjupiter.javafx;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * Data access object
 * 
 * @author Julian Jupiter
 *
 */
class UserDao {

	private static final Logger logger = Logger.getLogger(UserDao.class.getName());

	public boolean userExists(String username) throws SQLException {
		Connection connection = null;
		PreparedStatement statement = null;
		List<User> users = new ArrayList<>();

		try {
			connection = Database.getDBConnection();
			connection.setAutoCommit(false);
			String query = "SELECT id, username, last_name, first_name, password FROM user WHERE username = ?";
			statement = connection.prepareStatement(query);
			int counter = 1;
			statement.setString(counter++, username);
			ResultSet resultSet = statement.executeQuery();
			while (resultSet.next()) {
				User user = new User();
				user.setId(resultSet.getInt(1));
				user.setUsername(resultSet.getString(2));
				user.setLastName(resultSet.getString(3));
				user.setFirstName(resultSet.getString(4));
				user.setPassword(resultSet.getString(5));
				users.add(user);
			}

			return users.isEmpty() ? false : true;
		} catch (SQLException exception) {
			logger.log(Level.SEVERE, exception.getMessage());
		} finally {
			if (null != statement) {
				statement.close();
			}

			if (null != connection) {
				connection.close();
			}
		}

		return users.isEmpty() ? false : true;
	}

	public int saveUser(User user) throws SQLException {
		Connection connection = null;
		PreparedStatement statement = null;
		ResultSet resultSet = null;
		try {
			connection = Database.getDBConnection();
			connection.setAutoCommit(false);
			String query = "INSERT INTO user(username, last_name, first_name, password) VALUES(?, ?, ?, ?)";
			statement = connection.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
			int counter = 1;
			statement.setString(counter++, user.getUsername());
			statement.setString(counter++, user.getLastName());
			statement.setString(counter++, user.getFirstName());
			statement.setString(counter++, user.getPassword());
			statement.executeUpdate();
			connection.commit();
			resultSet = statement.getGeneratedKeys();
			if (resultSet.next()) {
				return resultSet.getInt(1);
			}
		} catch (SQLException exception) {
			logger.log(Level.SEVERE, exception.getMessage());
			if (null != connection) {
				connection.rollback();
			}
		} finally {
			if (null != resultSet) {
				resultSet.close();
			}

			if (null != statement) {
				statement.close();
			}

			if (null != connection) {
				connection.close();
			}
		}

		return 0;
	}

}