利用JavaFX访问MySQL数据库

Posted 2020-10-16 zeroingToOne

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