利用JavaFX访问MySQL数据库
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
