使用 JavaFX 从 MYSQL 数据库向 table 添加新用户无效

Question

我进行了搜索，但找不到解决方案，因为 google 搜索中的示例与我的编程风格不符。

编辑：我用addUser方法解决了问题。

MySQL 中的日期格式为 YYY-MM-DD。在我的 DatePicker 中是 DD.MM.YYY。如何解决这个问题？我是否必须更改数据库或 java 文件中的某些内容？

package application;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.geometry.Insets;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.ButtonBar;
import javafx.scene.control.DatePicker;
import javafx.scene.control.Label;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.TextField;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.ColumnConstraints;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.HBox;
import javafx.scene.text.Font;

public class Main extends Application {

    private BorderPane root;
    private Scene scene;
    private GridPane grid;

    private Label lblFirstName;
    private Label lblLastName;
    private Label lblDOB;

    private TextField txtFirstName;
    private TextField txtLastName;
    private DatePicker txtDOB;

    private Button btnAdd;
    private Button btnCancel;
    private Button btnUpdate;

    private HBox hbox;

    private ButtonBar buttonBar;

    private TableView<User> table;

    final ObservableList<User> data = FXCollections.observableArrayList();

    Connection conn;
    PreparedStatement pst = null;
    ResultSet rs = null;

    String url = "jdbc:mysql://localhost:3306/...";
    String user = "root";
    String password = "...";

    @Override
    public void start(Stage primaryStage) {
        try {
            CheckConnection();

            root = new BorderPane();
            grid = new GridPane();

            // Create  labels and textfields
            lblFirstName = new Label("First Name");
            lblFirstName.setFont(new Font("Times New Roman", 18));
            lblFirstName.setPrefSize(100, 50);

            lblLastName = new Label("Last Name");
            lblLastName.setFont(new Font("Times New Roman", 18));
            lblLastName.setPrefSize(100, 50);

            lblDOB = new Label("DOB");
            lblDOB.setFont(new Font("Times New Roman", 18));
            lblDOB.setPrefSize(150, 50);

            txtFirstName = new TextField();
            txtLastName = new TextField();
            txtDOB = new DatePicker();

            // add to grid
            grid.add(lblFirstName, 0, 0, 1, 1);
            grid.add(txtFirstName, 1, 0, 1, 1);
            grid.add(lblLastName, 0, 1, 1, 1);
            grid.add(txtLastName, 1, 1, 1, 1);
            grid.add(lblDOB, 0, 2, 1, 1);
            grid.add(txtDOB, 1, 2, 1, 1);

            grid.setHgap(10);
            grid.setVgap(5);

            grid.setPadding(new Insets(50, 10, 10, 30));

            // Column constraints
            ColumnConstraints column1 = new ColumnConstraints();
            ColumnConstraints column2 = new ColumnConstraints();

            grid.getColumnConstraints().add(column1);
            grid.getColumnConstraints().add(column2);

            column1.setPrefWidth(110);
            column2.setPrefWidth(200);

            // Buttons, Button Actions, ButtonBar
            btnAdd = new Button("Add");
            btnAdd.setPrefSize(40, 40);
            btnAdd.setOnAction(e -> {
                addUser();
            });

            btnCancel = new Button("Cancel");
            btnCancel.setPrefSize(40, 40);
            btnCancel.setOnAction(e -> {
                clearFields();
            });

            btnUpdate = new Button("Update");
            btnUpdate.setPrefSize(40, 40);
            btnUpdate.setOnAction(e -> {
                updateTable();
            });

            buttonBar = new ButtonBar();
            buttonBar.getButtons().addAll(btnAdd, btnCancel, btnUpdate);

            // add ButtonBar to HBox
            hbox = new HBox();
            hbox.getChildren().add(buttonBar);
            hbox.setPadding(new Insets(10));

            // create table
            table = new TableView<>();

            TableColumn<User, String> IDColumn = new TableColumn<User, String>("PersonID");
            IDColumn.setPrefWidth(100);
            IDColumn.setCellValueFactory(new PropertyValueFactory<>("personID"));

            TableColumn<User, String> vornameColumn = new TableColumn<User, String>("First Name");
            vornameColumn.setPrefWidth(100);
            vornameColumn.setCellValueFactory(new PropertyValueFactory<>("firstName"));

            TableColumn<User, String> nachnameColumn = new TableColumn<User, String>("Last Name");
            nachnameColumn.setPrefWidth(100);
            nachnameColumn.setCellValueFactory(new PropertyValueFactory<>("lastName"));

            TableColumn<User, String> dobColumn = new TableColumn<User, String>("DOB");
            dobColumn.setPrefWidth(100);
            dobColumn.setCellValueFactory(new PropertyValueFactory<>("dob"));

            table.getColumns().addAll(IDColumn, vornameColumn, nachnameColumn, dobColumn);

            root.setCenter(table);
            BorderPane.setMargin(table, new Insets(10, 10, 10, 10));
            root.setLeft(grid);
            root.setBottom(hbox);

            scene = new Scene(root, 1000, 500);
            scene.getStylesheets().add(getClass().getResource("application.css").toExternalForm());
            primaryStage.setScene(scene);
            primaryStage.show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public void CheckConnection() {
        conn = DBConnection.DbConnector();
        if (conn == null) {
            System.out.println("Connection Not Successful");
            System.exit(1);
        } else {
            System.out.println("Connection Successful");
        }
    }

    public void updateTable() {
        data.clear();  
        try {
            String query = "SELECT * FROM persons ";
            pst = conn.prepareStatement(query);
            rs = pst.executeQuery();
            while (rs.next()) {
                data.add(new User(rs.getString("PersonID"), rs.getString("Firstname"), rs.getString("Lastname"),
                        rs.getString("DOB")
                ));
                table.setItems(data);
            }
            pst.close();
            rs.close();
        } catch (Exception e1) {
            System.err.println(e1);
        }
    }

    public void addUser() {
        try {
            conn = DBConnection.DbConnector();
            String query = "INSERT into persons (Firstname, Lastname, DOB) VALUES (?, ?, ?)";
            pst = conn.prepareStatement(query);

            pst.setString(1, txtFirstName.getText());
            pst.setString(2, txtLastName.getText());
            pst.setString(3, ((TextField)txtDOB.getEditor()).getText());

            pst.executeUpdate();
            pst.close();
        } catch (Exception e2) {
            System.err.println(e2);
        }
    }

    public void clearFields() {
        txtFirstName.clear();
        txtLastName.clear();
        txtDOB.setValue(null);
    }

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

package application;

import javafx.beans.property.SimpleStringProperty;

public class User {
    private SimpleStringProperty personID;
    private SimpleStringProperty firstName;
    private SimpleStringProperty lastName;
    private SimpleStringProperty dob;

    public User(String pID, String fName, String lName, String DOB) {
        this.personID = new SimpleStringProperty(pID);
        this.firstName = new SimpleStringProperty(fName);
        this.lastName = new SimpleStringProperty(lName);
        this.dob = new SimpleStringProperty(DOB);
    }

    // getter , setter
    public String getPersonID() {
        return personID.get();
    }

    public void setPersonenID(String pID) {
        personID.set(pID);
    }

    public String getFirstName() {
        return firstName.get();
    }

    public void setFirstName(String fName) {
        firstName.set(fName);
    }

    public String getLastName() {
        return lastName.get();
    }

    public void setLastName(String lName) {
        lastName.set(lName);
    }

    public String getDob() {
        return dob.get();
    }

    public void setDob(String DOB) {
        dob.set(DOB);
    }
}

package application;

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

public class DBConnection {

    static String url ="jdbc:mysql://localhost:3306/...";         
    static String user ="root";
    static String password="...";

    public static Connection DbConnector(){        
        try{
            Connection conn = DriverManager.getConnection(url, user, password);
            return conn;
        } catch (SQLException ex) {
            System.err.println(ex.getMessage());
        }
        return null;
    }
}

Answer 1

我从你那里了解到 that the data type of column DOB, in database table persons is DATE。因此，格式无关紧要，因为即使 DATE 类型的文档包括以下内容：

The DATE type is used for values with a date part but no time part. MySQL retrieves and displays DATE values in 'YYYY-MM-DD' format. The supported range is '1000-01-01' to '9999-12-31'.

我认为这是误导，因为根据 storage requirements 文档，DATE 值存储在三个字节中。所以该格式仅用于人类可读显示。

因此，由于格式无关紧要，您的问题基本上是如何获取 DatePicker 值并将其插入到 persons 数据库 table 的 DOB 列中。

方法getValue()，在classDatePicker，returns一个LocalDate.

如果您正在使用 MySQL 连接器，则根据 documentation，DATE 数据类型映射到 java class java.sql.Date.

因此您需要将 java.time.LocalDate 转换为 java.sql.Date。您可以通过在 class java.sql.Date 中调用静态方法 valueOf() 来完成此操作。参考 SO问题。

这是我重写的 addUser() 方法版本。它使用 try-with-resources.

public void addUser() {
    String query = "INSERT into persons (Firstname, Lastname, DOB) VALUES (?, ?, ?)";
    try (conn = DBConnection.DbConnector();
         pst = conn.prepareStatement(query)) {
        pst.setString(1, txtFirstName.getText());
        pst.setString(2, txtLastName.getText());
        pst.setDate(3, java.sql.Date.valueOf(txtDOB.getValue()));
        pst.executeUpdate();
    }
    catch (SQLException xSql) {
        xSql.printStackTrace();
    }
}

如果你还想改变DatePicker显示的日期格式，你可以设置它的converter property. The below code demonstrates how to do this using an anonymous class。

DatePicker txtDOB = new DatePicker();
txtDOB.setConverter(new StringConverter<LocalDate>() {
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy", Locale.ENGLISH);

    @Override
    public String toString(LocalDate object) {
        if (object != null) {
            return object.format(formatter);
        }
        return null;
    }

    @Override
    public LocalDate fromString(String string) {
        if (string != null) {
            return LocalDate.parse(string, formatter);
        }
        return null;
    }
});

使用 JavaFX 从 MYSQL 数据库向 table 添加新用户无效

Adding new User to a table from MYSQL database using JavaFX is not working

mysql

javafx