java - 我正在使用 JavaFX，并且我的组合框不想从 sql 数据库填充

Question

我想做的是在应用程序加载时使用我的 Travelexperts 数据库中的 AgentID 填充我的组合框。

我认为问题出在 Controller 类的某个地方。我没有得到任何异常，但如果我尝试从其中一个按钮运行 buildCombo() 方法而不是初始化，我会得到一个类未找到异常

Controller 类:

package sample;

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

import javafx.beans.Observable;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.control.ComboBox;
import javafx.scene.control.TextField;
import javafx.scene.input.MouseEvent;

public class Controller {

    Connection conn;

    @FXML
    private ResourceBundle resources;

    @FXML
    private URL location;

    @FXML
    private TextField tvAgentID;

    @FXML
    private TextField tvFirstName;

    @FXML
    private TextField tvMiddleInitial;

    @FXML
    private TextField tvLastName;

    @FXML
    private TextField tvPhone;

    @FXML
    private TextField tvEmail;

    @FXML
    private TextField tvPosition;

    @FXML
    private TextField tvAgencyID;

    @FXML
    private Button btnSave;

    @FXML
    private Button btnEdit;

    @FXML
    private ComboBox cmbAgentID;

    public Controller() throws SQLException {
    }

    @FXML
    void cmbClicked(MouseEvent event) {

    }

    @FXML
    void editClicked(MouseEvent event) {

    }

    @FXML
    void saveClicked(MouseEvent event) throws SQLException, ClassNotFoundException {
        updateAgent();
    }



    /////////////////////////////METHODS/////////////////////


    private void buildCombo() throws SQLException, ClassNotFoundException {
        // TODO Auto-generated method stub
        Connection conn;
        Class.forName("com.mysql.cj.jdbc.Driver");

        conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/travelexperts",
                "Sander", "********");
        ObservableList<Agent> data = FXCollections.observableArrayList();
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery("select AgentId from agents");
        while (rs.next()) {
            data.add(new Agent(rs.getInt("agentID")));
        }
        cmbAgentID.setItems(data);
    }

    ///////////////////INITIALIZE/////////////////////////////
    @FXML
    public void initialize(URL location, ResourceBundle resources) throws SQLException, ClassNotFoundException {
        assert tvAgentID != null : "fx:id=\"tvAgentID\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvFirstName != null : "fx:id=\"tvFirstName\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvMiddleInitial != null : "fx:id=\"tvMiddleInitial\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvLastName != null : "fx:id=\"tvLastName\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvPhone != null : "fx:id=\"tvPhone\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvEmail != null : "fx:id=\"tvEmail\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvPosition != null : "fx:id=\"tvPosition\" was not injected: check your FXML file 'sample.fxml'.";
        assert tvAgencyID != null : "fx:id=\"tvAgencyID\" was not injected: check your FXML file 'sample.fxml'.";
        assert btnSave != null : "fx:id=\"btnSave\" was not injected: check your FXML file 'sample.fxml'.";
        assert btnEdit != null : "fx:id=\"btnEdit\" was not injected: check your FXML file 'sample.fxml'.";
        assert cmbAgentID != null : "fx:id=\"cmbAgentID\" was not injected: check your FXML file 'sample.fxml'.";
        btnSave.setStyle("-fx-background-color: cornflowerblue");
        btnEdit.setStyle("-fx-background-color: cornflowerblue");
        try {
            conn = new DB().getConnection();
            buildCombo();
        } catch (ClassNotFoundException | SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

数据库类:

package sample;

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

public class DB {

    public Connection getConnection() throws ClassNotFoundException, SQLException
    {
        Class.forName("com.mysql.jdbc.Driver");
        return DriverManager.getConnection(
                "jdbc:mysql://localhost:3306/travelexperts",
                "Sander",
                "*******"
        );
    }
}

主类:

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception{
        Parent root = FXMLLoader.load(getClass().getResource("sample.fxml"));
        primaryStage.setTitle("Hello World");
        primaryStage.setScene(new Scene(root, 800, 500));
        primaryStage.show();
    }


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

示例类:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.Button?>
<?import javafx.scene.control.ComboBox?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>

<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
   <children>
      <TextField fx:id="tvAgentID" layoutX="14.0" layoutY="52.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvFirstName" layoutX="143.0" layoutY="52.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvMiddleInitial" layoutX="290.0" layoutY="49.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvLastName" layoutX="447.0" layoutY="52.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvPhone" layoutX="24.0" layoutY="321.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvEmail" layoutX="161.0" layoutY="321.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvPosition" layoutX="317.0" layoutY="321.0" prefHeight="26.0" prefWidth="89.0" />
      <TextField fx:id="tvAgencyID" layoutX="475.0" layoutY="321.0" prefHeight="26.0" prefWidth="89.0" />
      <Label alignment="CENTER" layoutX="18.0" layoutY="11.0" prefHeight="26.0" prefWidth="81.0" text="AgentID" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="147.0" layoutY="14.0" prefHeight="26.0" prefWidth="81.0" text="First Name" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="294.0" layoutY="14.0" prefHeight="26.0" prefWidth="90.0" text="Middle Initial" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="451.0" layoutY="14.0" prefHeight="26.0" prefWidth="81.0" text="Last Name" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="28.0" layoutY="298.0" prefHeight="26.0" prefWidth="81.0" text="Phone" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="165.0" layoutY="298.0" prefHeight="26.0" prefWidth="81.0" text="Email" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="321.0" layoutY="298.0" prefHeight="26.0" prefWidth="81.0" text="Position" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label alignment="CENTER" layoutX="479.0" layoutY="298.0" prefHeight="26.0" prefWidth="81.0" text="AgencyID" textAlignment="CENTER">
         <font>
            <Font name="System Bold" size="14.0" />
         </font>
      </Label>
      <Label layoutX="14.0" layoutY="123.0" prefHeight="62.0" prefWidth="235.0" text="EDIT AN AGENT">
         <font>
            <Font name="System Bold" size="24.0" />
         </font>
      </Label>
      <Button fx:id="btnSave" layoutX="447.0" layoutY="126.0" mnemonicParsing="false" onMouseClicked="#saveClicked" prefHeight="56.0" prefWidth="120.0" text="Save" />
      <Button fx:id="btnEdit" layoutX="447.0" layoutY="200.0" mnemonicParsing="false" onMouseClicked="#editClicked" prefHeight="56.0" prefWidth="120.0" text="Edit" />
      <ComboBox fx:id="cmbAgentID" layoutX="235.0" layoutY="140.0" onMouseClicked="#cmbClicked" prefHeight="28.0" prefWidth="130.0" />
   </children>
</AnchorPane>

代理类别:

package sample;

public class Agent {

    private int agentID;
    private String firstName;
    private String middleInitial;
    private String lastName;
    private String businessPhone;
    private String email;
    private String position;
    private int agencyID;

    //////////////Constructors////////////////

    public Agent(int agentID, String firstName, String middleInitial, String lastName,
                 String businessPhone, String email, String position, int agencyID) {
        this.agentID = agentID;
        this.firstName = firstName;
        this.middleInitial = middleInitial;
        this.lastName = lastName;
        this.businessPhone = businessPhone;
        this.email = email;
        this.position = position;
        this.agencyID = agencyID;
    }

    public Agent(int agentID) {
        this.agentID = agentID;
    }

Answer 1

在您的DB Class中，您使用了正确的MySQL驱动程序，但在您的buildCombo()方法中，您使用了错误/已弃用的MySQL驱动程序，请更改Class .forName("com.mysql.cj.jdbc.Driver"); 到 Class.forName("com.mysql.jdbc.Driver"); 就像你在 中一样DB Class 它应该可以工作。另外，在控制台中打印出ResultSet rs，这样您就可以确定在那里得到了一些结果。