javafx登录界面连接数据库

要连接数据库，您需要使用Java Database Connectivity（JDBC）API。以下是一个简单的JavaFX登录界面示例，其中使用JDBC连接到MySQL数据库：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import javafx.application.Application;
import javafx.geometry.Insets;
import javafx.scene.Scene;
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.stage.Stage;

public class LoginApp extends Application {

    private static final String DB_URL = "jdbc:mysql://localhost:3306/mydatabase";
    private static final String DB_USER = "root";
    private static final String DB_PASSWORD = "password";

    private static final String LOGIN_QUERY = "SELECT * FROM users WHERE username = ? AND password = ?";

    private TextField usernameField;
    private PasswordField passwordField;
    private Label statusLabel;

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

        GridPane grid = new GridPane();
        grid.setPadding(new Insets(10, 10, 10, 10));
        grid.setVgap(5);
        grid.setHgap(5);

        Label usernameLabel = new Label("Username:");
        GridPane.setConstraints(usernameLabel, 0, 0);
        usernameField = new TextField();
        GridPane.setConstraints(usernameField, 1, 0);

        Label passwordLabel = new Label("Password:");
        GridPane.setConstraints(passwordLabel, 0, 1);
        passwordField = new PasswordField();
        GridPane.setConstraints(passwordField, 1, 1);

        Button loginButton = new Button("Login");
        GridPane.setConstraints(loginButton, 1, 2);
        loginButton.setOnAction(e -> handleLogin());

        statusLabel = new Label();
        GridPane.setConstraints(statusLabel, 1, 3);

        grid.getChildren().addAll(usernameLabel, usernameField, passwordLabel, passwordField, loginButton, statusLabel);

        Scene scene = new Scene(grid, 300, 150);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private void handleLogin() {
        String username = usernameField.getText();
        String password = passwordField.getText();

        try {
            Connection conn = DriverManager.getConnection(DB_URL, DB_USER, DB_PASSWORD);
            PreparedStatement stmt = conn.prepareStatement(LOGIN_QUERY);
            stmt.setString(1, username);
            stmt.setString(2, password);
            ResultSet rs = stmt.executeQuery();

            if (rs.next()) {
                statusLabel.setText("Login successful");
            } else {
                statusLabel.setText("Incorrect username or password");
            }

            conn.close();
        } catch (SQLException e) {
            statusLabel.setText("Database error");
            e.printStackTrace();
        }
    }

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

}

在这个示例中，我们使用了一个GridPane布局，包含了一个用户名文本框、一个密码文本框、一个登录按钮和一个状态标签。当用户点击登录按钮时，我们使用JDBC连接到MySQL数据库，执行一个查询来检查用户提供的用户名和密码是否正确。如果查询返回结果，则显示“登录成功”消息，否则显示“用户名或密码不正确”消息。如果发生数据库错误，则显示“数据库错误”消息。

请注意，这个示例中使用的是MySQL数据库，您需要将DB_URL、DB_USER和DB_PASSWORD变量替换为您自己的数据库连接信息。此外，您还需要下载MySQL JDBC驱动程序，并将其添加到您的项目中。