利用JavaFX访问MySQL数据库

2023-08-21 16:56:10

1. 创建数据库表

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. 创建JavaFX项目

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();// 存放查询结果

    @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();// 获取输入的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);// 查询数据库，并返回查询结果

　　　　　　　　　　　　　　　　if (rSet.next()) {// 显示查询结果

                            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();

        }

    }

}

运行结果：输入SSN和courseID，显示查询结果，如图。

另1：在eclipse中安装JavaFX

点击eclipse中的Help->Install New Software，在弹出的窗口中设置如下：

点击Work with框后的Add，在弹出的窗口中，设置如下：Name: ex(fx)lipse，Location：http://download.eclipse.org/efxclipse/updates-released/2.3.0/site/ ，点击OK。上述设置好后，会发现两个插件的复选框：e(fx)clipse – install 安装和e(fx)clipse – single components，选中这两个复选框，完成安装。

另2：开始程序一直报错：Not unique table/alias: 'student'，网上查询是因为跟MySQL关键字重名，但并没有重名的字段，最后发现是SQL语句在换行时少了一个空格，因此要注意SQL语句在换行时的空格情况。

3. 利用PreparedStatement创建参数和的SQL语句

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();// 存放查询结果

    @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";//问号作为参数的占位符

                        preparedStatement = conn.prepareStatement(queryString);

                        preparedStatement.setString(1, ssn);//设置占位符处的参数值

                        preparedStatement.setString(2, courseId);

                        ResultSet rSet = preparedStatement.executeQuery();//执行查询语句

　　　　　　　　　　　　　　　　if (rSet.next()) {// 显示查询结果

                            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;

    }

}

参考资料：Java语言程序设计进阶版

码农公寓

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