我试图让gui，谁将员工添加到数据库。我正在撰写这篇文章，因为我遇到了错误。
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Node.fireEvent(Node.java:8413)
at javafx.scene.control.Button.fire(Button.java:185)
at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
at javafx.event.Event.fireEvent(Event.java:198)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:432)
at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
at com.sun.glass.ui.View.notifyMouse(View.java:937)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
... 48 more
Caused by: java.lang.NullPointerException
at addEmployee.addEmployeeController.add(addEmployeeController.java:38)
... 58 more
Process finished with exit code 0
addEmployee.fxml
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.112" xmlns:fx="http://javafx.com/fxml/1" fx:controller="addEmployee.addEmployeeController">
<children>
<TextField fx:id="nameTF" layoutX="205.0" layoutY="57.0" promptText="name" />
<TextField fx:id="surnameTF" layoutX="205.0" layoutY="103.0" promptText="surname" />
<TextField fx:id="ageTF" layoutX="205.0" layoutY="143.0" promptText="age" />
<Button fx:id="addBTN" layoutX="205.0" layoutY="188.0" mnemonicParsing="false" onAction="#add" text="Add" />
<Button fx:id="cancelBTN" layoutX="300.0" layoutY="188.0" mnemonicParsing="false" onAction="#cancel" text="Cancel" />
</children>
</AnchorPane>
addEmployeeController
package addEmployee;
import Database.DatabaseHandler;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.*;
import java.net.URL;
import java.util.ResourceBundle;
public class addEmployeeController implements Initializable{
DatabaseHandler databaseHandler;
@FXML
private TextField name;
@FXML
private TextField surname;
@FXML
private TextField age;
@FXML
private Button add;
@FXML
private Button cancel;
@Override
public void initialize(URL location, ResourceBundle resources) {
databaseHandler = new DatabaseHandler();
}
@FXML
private void add(ActionEvent actionEvent) {
String employeeName = name.getText();
String employeeSurname = surname.getText();
String employeeAge = age.getText();
if (employeeName.isEmpty() || employeeSurname.isEmpty() || employeeAge.isEmpty()){
Alert alert = new Alert(Alert.AlertType.ERROR);
alert.setHeaderText(null);
alert.setContentText("Please enter in all fields");
alert.showAndWait();
return;
}
String qu = "INSERT INTO Employees VALUES ("
+"'"+employeeName+",'"
+"'"+employeeSurname+",'"
+""+employeeAge+""
+")";
System.out.println(qu);
if (databaseHandler.execAction(qu)) {
Alert alert = new Alert(Alert.AlertType.INFORMATION);
alert.setHeaderText(null);
alert.setContentText("Succes");
alert.showAndWait();
}else//error
{
Alert alert = new Alert(Alert.AlertType.ERROR);
alert.setHeaderText(null);
alert.setContentText("Failed");
alert.showAndWait();
}
}
public void cancel(ActionEvent actionEvent) {
}
}
主要
package addEmployee;
import Database.DatabaseHandler;
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("/addEmployee/addEmployee.fxml"));
primaryStage.setTitle("Hello World");
primaryStage.setScene(new Scene(root, 300, 275));
primaryStage.show();
}
public static void main(String[] args) {
launch(args);
}
}
数据库处理器
package Database;
import java.sql.*;
public class DatabaseHandler {
public static final String Driver = "org.sqlite.JDBC";
private static final String DB_URL = "jdbc:sqlite:TEST.db";
private static Connection connection = null;
private static Statement statement = null;
public DatabaseHandler() {
try {
Class.forName(DatabaseHandler.Driver);
} catch (ClassNotFoundException e) {
System.out.println("No driver JDBC");
e.printStackTrace();
}
try {
connection = DriverManager.getConnection(DB_URL);
statement = connection.createStatement();
} catch (SQLException e) {
System.out.println("Problem with opening the connection");
e.printStackTrace();
}
createTables();
}
public boolean createTables() {
String createEmployees = "CREATE TABLE IF NOT EXISTS Employees (Employee_id INTEGER PRIMARY KEY AUTOINCREMENT, name varchar(255), surname varchar(255), age int)";
try {
statement.execute(createEmployees);
} catch (SQLException e) {
System.out.println("Problem with creating a table");
e.printStackTrace();
return false;
}
return true;
}
public boolean insertEmployees(String name, String surname, int age) {
try {
PreparedStatement preparedStatement = connection.prepareStatement("insert into Employees values (NULL,?,?,?);");
preparedStatement.setString(1,name);
preparedStatement.setString(2,surname);
preparedStatement.setInt(3,age);
preparedStatement.execute();
} catch (SQLException e) {
System.out.println("Error with insert an employee to the table");
e.printStackTrace();
return false;
}
return true;
}
public ResultSet execQuery(String query){
ResultSet resultSet;
try {
statement = connection.createStatement();
resultSet = statement.executeQuery(query);
}catch (SQLException e){
System.out.println("Error in exec query\n"+e.getMessage());
return null;
}finally {
}
return resultSet;
}
public boolean execAction(String qu){
try {
statement = connection.createStatement();
statement.execute(qu);
return true;
}catch (SQLException e){
System.out.println("excecption at exec action\n"+e.getMessage());
return false;
}finally {
}
}
public void closeConnection() {
try {
connection.close();
} catch (SQLException e) {
System.err.println("Error with shutdown");
e.printStackTrace();
}
}
}
我的程序运行正常，但是当我点击“添加”按钮时，我收到此错误。我怎么修理它？你能和我联系一些好的教程来制作合适的gui吗？