Question

我试图找出如何使用删除按钮来从sqlite数据库删除数据。我设法从tableview中删除一行。

我设法成功删除数据的唯一方法是指定查询要删除哪一行。所以问题是我做错了什么？

以下是我遇到问题的代码部分：

package Medic;

import dbUtil.dbConnection;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.*;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.Stage;


import java.net.URL;
import java.sql.*;
import java.util.ResourceBundle;

public class MedicController implements Initializable {
    @FXML
    private Button deleteButton;
    @FXML
    private Button closeButton;
    @FXML
    private TextField id;
    @FXML
    private TextField firstname;
    @FXML
    private TextField lastname;
    @FXML
    private TextField email;
    @FXML
    private DatePicker dob;

    @FXML
    private TableView<PacientiData> ptable;

    @FXML
    private TableColumn<PacientiData, String> idcolumn;
    @FXML
    private TableColumn<PacientiData, String> firstnamecolumn;
    @FXML
    private TableColumn<PacientiData, String> lastnamecolumn;
    @FXML
    private TableColumn<PacientiData, String> emailcolumn;
    @FXML
    private TableColumn<PacientiData, String> dobcolumn;


    private dbConnection dc;
    private ObservableList<PacientiData> data;
    private String sql = "SELECT * FROM pacienti";


    @Override
    public void initialize(URL location, ResourceBundle resources) {

        this.dc = new dbConnection();
    }

    @FXML
    private void loadStudentData(ActionEvent actionEvent) {
        try {
            Connection conn = dbConnection.getConnection();

            this.data = FXCollections.observableArrayList();

            ResultSet rs = conn.createStatement().executeQuery(sql);

            while (rs.next()) {
                this.data.add(new PacientiData(rs.getString(1), rs.getString(2), rs.getString(3), rs.getString(4), rs.getString(5)));
            }
        } catch (SQLException ex) {
            System.out.println("Error " + ex);
        }
        this.idcolumn.setCellValueFactory(new PropertyValueFactory<PacientiData, String>("ID"));
        this.firstnamecolumn.setCellValueFactory(new PropertyValueFactory<PacientiData, String>("firstName"));
        this.lastnamecolumn.setCellValueFactory(new PropertyValueFactory<PacientiData, String>("lastName"));
        this.emailcolumn.setCellValueFactory(new PropertyValueFactory<PacientiData, String>("email"));
        this.dobcolumn.setCellValueFactory(new PropertyValueFactory<PacientiData, String>("DOB"));

        this.ptable.setItems(null);
        this.ptable.setItems(this.data);

    }

    @FXML
    private void addStudent(ActionEvent actionEvent) {
        String sqlInsert = "INSERT INTO pacienti(id,fname,lname,email,DOB) VALUES(?,?,?,?,?)";
        try {

            Connection conn = dbConnection.getConnection();
            PreparedStatement statement = conn.prepareStatement(sqlInsert);
            statement.setString(1, this.id.getText());
            statement.setString(2, this.firstname.getText());
            statement.setString(3, this.lastname.getText());
            statement.setString(4, this.email.getText());
            statement.setString(5, this.dob.getEditor().getText());
            statement.execute();
            conn.close();


        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    @FXML
    private void clearFields(ActionEvent actionEvent) {
        this.id.setText("");
        this.firstname.setText("");
        this.lastname.setText("");
        this.email.setText("");
        this.dob.setValue(null);
    }


    @FXML
    public void handleCloseButtonAction(ActionEvent event) {
        Stage stage = (Stage) closeButton.getScene().getWindow();
        stage.close();
    }


    @FXML

    public void deleteButton(ActionEvent event) {
        Connection conn = null;
        Statement statement = null;

        try {
            Class.forName("org.sqlite.JDBC");
            conn = DriverManager.getConnection("jdbc:sqlite:database.sqlite");
            conn.setAutoCommit(false);
            System.out.println("Opened database succesfully");
            int selectedIndex = ptable.getSelectionModel().getSelectedIndex();
            ptable.getItems().remove(selectedIndex);
            statement = conn.createStatement();
            String sqldelete =" DELETE FROM pacienti WHERE id = ? ";
            statement.executeUpdate(sqldelete);
            conn.commit();

            ResultSet rs = statement.executeQuery("SELECT * FROM pacienti ");

            while (rs.next() ) {
                int id = rs.getInt("id");
                String fname = rs.getString("fname");
                String lname = rs.getString("lname");
                String email = rs.getString("email");
                String DOB = rs.getString("DOB");
            }

            rs.close();
            statement.close();
            conn.close();
        }
        catch (Exception e ) {
            e.printStackTrace();
        }
    }
}

enter image description here

Answer 1

您的问题是什么

此代码存在问题，因为永远不会指定要删除的id的值：

Statement statement = null;
statement = conn.createStatement();
String sqldelete =" DELETE FROM pacienti WHERE id = ? ";
statement.executeUpdate(sqldelete);

如果您没有告诉它要删除什么，它怎么可能知道删除什么？

我可能无法验证其他问题，因为我无法在您的数据库上试用您的完整程序，但至少以上是一个问题。

如何解决

您应该使用PreparedStatement并设置ID：

PreparedStatement statement = conn.prepareStatement(
    "DELETE FROM pacienti WHERE id = ?"
);
statement.setInt(1, id);
statement.executeUpdate();

id的值应该是什么，从您的示例中不清楚。我的猜测是你会使用类似下面的东西，假设你的模型类中存在适当的id值和存取方法：

Student selectedStudent = studenttable.getSelectionModel().getSelectedItem();
int id = selectedStudent.getId();

关于提议的解决方案的几点说明

我使用int因为我不知道您的模型如何表达ID，但如果可能是大量学生或long，您可以使用String如果ID是UUID。

如果没有选择任何内容（因为没有要删除的内容），您不希望删除运行，那么在初始化时，您可以将删除按钮的禁用属性绑定到所选项目列表。

 deleteButton.disableProperty().bind(
      Bindings.isEmpty(studenttable.getSelectionModel().getSelectedItems())
 );

我提供的代码用于SingleSelectionModel，其中一次只选择一个项目进行删除。如果使用MultipleSelectionModel，则需要使用getSelectedItems（）而不是getSelectedItem（），并确保删除所有选定的项目，而不是仅删除一个。

从JavaFX GUI删除sqlite数据库中的数据

1 个答案: