利用JavaFX訪問MySQL數據庫

1. 創建數據庫表

create table Course(
courseId char(5),
subjectId char(4) not null,
courseNumber integer,
title varchar(50) not null,
numOfCredits integer,
primary key (courseId)
);

create table Student(
ssn char(9),
firstName varchar(25),
mi char(1),
lastName varchar(25),
birthDate date,
street varchar(25),
phone char(11),
zipCode char(5),
deptId char(4),
primary key (ssn)
);

create table Enrollment(
ssn char(9),
courseId char(15),
dateRegistered date,
grade char(1),
primary key (ssn, courseId),
foreign key (ssn) references Student(ssn),
foreign key (courseId) references Course(courseId)
);

2. 創建JavaFX項目

package application;

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

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Main extends Application {
    private Statement stmt;
    private TextField tfSSN = new TextField(); 
    private TextField tfCourseId = new TextField();
    private Label lblStatus = new Label();// 存放查詢結果

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

            Button bsShowGrade = new Button("Show Grade");
            HBox hBox = new HBox(5);
            hBox.getChildren().addAll(new Label("SSN"), tfSSN, new Label("Course Id"), tfCourseId, bsShowGrade);

            VBox vBox = new VBox(10);
            vBox.getChildren().addAll(hBox, lblStatus);

            tfSSN.setPrefColumnCount(6);
            tfCourseId.setPrefColumnCount(6);
            bsShowGrade.setOnAction(new EventHandler<ActionEvent>() {

                @Override
                public void handle(ActionEvent arg0) {
                    // TODO Auto-generated method stub
                    String ssn = tfSSN.getText();// 獲取輸入的SSN
                    String courseId = tfCourseId.getText();
                    try {
                        String queryString ="select firstName, mi, lastName, title, grade from Student, Enrollment, Course" +
                                   " where Student.ssn = '"+ssn+"' and Enrollment.courseId "
                                           + "= '"+courseId+"' and Enrollment.courseId = Course.courseId"
                                           + " and Enrollment.ssn = Student.ssn";
                        String queryStrin = "select firstName, mi, lastName, grade from student, Enrollment where Student.ssn = '11' and Enrollment.ssn = Student.ssn";
                        ResultSet rSet = stmt.executeQuery(queryString);// 查詢數據庫，並返回查詢結果

　　　　　　　　　　　　　　　　if (rSet.next()) {// 顯示查詢結果
                            String firstName = rSet.getString(1);
                            String mi = rSet.getString(2);
                            String lastName = rSet.getString(3);
                            String title = rSet.getString(4);
                            String grade = rSet.getString(5);

                            lblStatus.setText(firstName + " " + mi + " " + lastName + " " + title + " " + grade);
                        } else {
                            lblStatus.setText("Not found");
                        }
                    } catch (SQLException ex) {
                        ex.printStackTrace();
                    }
                }
            });

            Scene scene = new Scene(vBox, 420, 80);
            primaryStage.setTitle("FindGrade");
            primaryStage.setScene(scene);
            primaryStage.show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

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

    private void initializeDB() {
        try {
            Class.forName("com.mysql.jdbc.Driver");

            Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/dbname", "user", "password");

            stmt = conn.createStatement();
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    

}

運行結果：輸入SSN和courseID，顯示查詢結果，如圖。

另1：在eclipse中安裝JavaFX

點擊eclipse中的Help->Install New Software，在彈出的窗口中設置如下：

點擊Work with框后的Add，在彈出的窗口中，設置如下：Name: ex(fx)lipse，Location：http://download.eclipse.org/efxclipse/updates-released/2.3.0/site/ ，點擊OK。上述設置好后，會發現兩個插件的復選框：e(fx)clipse – install 安裝和e(fx)clipse – single components，選中這兩個復選框，完成安裝。

另2：開始程序一直報錯：Not unique table/alias: 'student'，網上查詢是因為跟MySQL關鍵字重名，但並沒有重名的字段，最后發現是SQL語句在換行時少了一個空格，因此要注意SQL語句在換行時的空格情況。

3. 利用PreparedStatement創建參數和的SQL語句

 

package application;

import java.sql.*;

import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class FindGradeUsingPreparedStatement extends Application{
    
    private PreparedStatement preparedStatement;
    private Statement stmt;
    private TextField tfSSN = new TextField(); 
    private TextField tfCourseId = new TextField();
    private Label lblStatus = new Label();// 存放查詢結果

    @Override
    public void start(Stage primaryStage) {
        try {
            Connection conn = initializeDB();

            Button bsShowGrade = new Button("Show Grade");
            HBox hBox = new HBox(5);
            hBox.getChildren().addAll(new Label("SSN"), tfSSN, new Label("Course Id"), tfCourseId, bsShowGrade);

            VBox vBox = new VBox(10);
            vBox.getChildren().addAll(hBox, lblStatus);

            tfSSN.setPrefColumnCount(6);
            tfCourseId.setPrefColumnCount(6);
            bsShowGrade.setOnAction(new EventHandler<ActionEvent>() {

                @Override
                public void handle(ActionEvent arg0) {
                    // TODO Auto-generated method stub
                    String ssn = tfSSN.getText();
                    String courseId = tfCourseId.getText();
                    try {
                        String queryString ="select firstName, mi, lastName, title, grade from Student, Enrollment, Course" +
                                   " where Student.ssn = ? and Enrollment.courseId "
                                           + "= ? and Enrollment.courseId = Course.courseId"
                                           + " and Enrollment.ssn = Student.ssn";//問號作為參數的占位符
                        preparedStatement = conn.prepareStatement(queryString);
                        
                        preparedStatement.setString(1, ssn);//設置占位符處的參數值
                        preparedStatement.setString(2, courseId);
                        ResultSet rSet = preparedStatement.executeQuery();//執行查詢語句

　　　　　　　　　　　　　　　　if (rSet.next()) {// 顯示查詢結果
                            String firstName = rSet.getString(1);
                            String mi = rSet.getString(2);
                            String lastName = rSet.getString(3);
                            String title = rSet.getString(4);
                            String grade = rSet.getString(5);

                            lblStatus.setText(firstName + " " + mi + " " + lastName + "'s grade on course " + title + " is " + grade);
                        } else {
                            lblStatus.setText("Not found");
                        }
                    } catch (SQLException ex) {
                        ex.printStackTrace();
                    }
                }
            });

            Scene scene = new Scene(vBox, 420, 80);
            primaryStage.setTitle("FindGrade");
            primaryStage.setScene(scene);
            primaryStage.show();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        launch(args);
    }
    private Connection initializeDB() {
        Connection conn = null;
        try {
            Class.forName("com.mysql.jdbc.Driver");

            conn = DriverManager.getConnection("jdbc:mysql://localhost/dbname", "user", "password");
            System.out.println("Database connected");
            
            
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return conn;
    }

}

 參考資料：Java語言程序設計 進階版