我正在研究JavaFX和SQL项目。 首先打开登录窗口，如果用户名和密码与我的数据库中存储的用户名和密码匹配，则将弹出AddCustomer deatils窗口[工作正常，直到此处]。我的数据库中将有一个表供用户输入。但是，当我单击“保存”按钮时，出现了这样的错误
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:8411)
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 sample.MysqlConnector.<init>(MysqlConnector.java:22)
at sample.AddCustomer.addcustomer(AddCustomer.java:52)
... 58 more
我的Main.java
package sample;
import javafx.application.Application;
import javafx.fxml.*;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;
public class Main extends Application {
@Override
public void start(Stage primaryStage) {
try {
Parent root = FXMLLoader.load(getClass().getResource("login1.fxml"));
primaryStage.setTitle("NOVOTEL HOTEL ");
primaryStage.setScene(new Scene(root, 500, 475));
primaryStage.show();
}
catch(Exception e )
{
e.printStackTrace();
}
}
public static void main(String[] args) {
launch(args);
}
}
My MysqlConnector.java
package sample;
import com.sun.istack.internal.NotNull;
import com.sun.istack.internal.Nullable;
import javafx.fxml.FXML;
import java.sql.*;
public class MysqlConnector {
@FXML
public static Statement stmt;
@FXML
public static Connection conn;
public MysqlConnector() {
Connector();
String TableName = "CustomerDetails";
try {
stmt = conn.createStatement();
DatabaseMetaData dbm = conn.getMetaData();
ResultSet tables = dbm.getTables(null, null, TableName.toUpperCase(), null);
if (tables.next()) {
System.out.println("Ready to go");
} else {
stmt.execute("CREARE TABLE " + TableName + "("
+ " customername varchar(45) primary key,"
+ " customername int" +
"+ customernumber int" +
"+ customerstay int" +
"+ customerguests varchar(45)"
+ ")");
}
} catch (SQLException e1) {
System.err.println(e1.getMessage());
}
}
@Nullable
@NotNull
public static Connection Connector() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/login", "root", "password");
return conn;
} catch (Exception e) {
return null;
}
}
@NotNull
@Nullable
public static ResultSet executeQuery(String query) {
ResultSet result ;
try {
stmt = conn.createStatement();
result=stmt.executeQuery(query);
} catch (SQLException e) {
System.out.println("Error here");
e.printStackTrace();
return null;
}
return result;
}
@NotNull
@Nullable
public boolean executeAction(String qu) {
try {
stmt = conn.createStatement();
stmt.execute(qu);
return true;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
}
我的LoginModel.java
package sample;
import com.sun.istack.internal.NotNull;
import com.sun.istack.internal.Nullable;
import javafx.fxml.FXML;
import java.sql.*;
public class MysqlConnector {
@FXML
public static Statement stmt;
@FXML
public static Connection conn;
public MysqlConnector() {
String TableName = "CustomerDetails";
try {
stmt = conn.createStatement();
DatabaseMetaData dbm = conn.getMetaData();
ResultSet tables = dbm.getTables(null, null, TableName.toUpperCase(), null);
if (tables.next()) {
System.out.println("Ready to go");
} else {
stmt.execute("CREARE TABLE " + TableName + "("
+ " customername varchar(45) primary key,"
+ " customername int" +
"+ customernumber int" +
"+ customerstay int" +
"+ customerguests varchar(45)"
+ ")");
}
} catch (SQLException e1) {
System.err.println(e1.getMessage());
}
}
@Nullable
@NotNull
public static Connection Connector() {
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/login", "root", "password");
return conn;
} catch (Exception e) {
return null;
}
}
@NotNull
@Nullable
public static ResultSet executeQuery(String query) {
ResultSet result ;
try {
stmt = conn.createStatement();
result=stmt.executeQuery(query);
} catch (SQLException e) {
System.out.println("Error here");
e.printStackTrace();
return null;
}
return result;
}
@NotNull
@Nullable
public boolean executeAction(String qu) {
try {
stmt = conn.createStatement();
stmt.execute(qu);
return true;
} catch (SQLException e) {
e.printStackTrace();
return false;
}
}
}
我的控制器类
import com.sun.istack.internal.Nullable;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.stage.*;
import javafx.scene.*;
import javafx.scene.layout.*;
import javafx.scene.control.*;
import javafx.geometry.*;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.control.TextField;
import java.net.URL;
import java.sql.SQLException;
import java.util.ResourceBundle;
import javafx.*;
public class Controller implements Initializable {
@NotNull
@Nullable
public LoginModel loginModel = new LoginModel();
@FXML
private Label isConnected,db;
@FXML
private TextField txtUsername;
@FXML
private TextField txtpassword;
@FXML
Button abutton = new Button("Login");
private AddCustomer addCustomer;
@Override
public void initialize(URL location, ResourceBundle resources) {
// TODO Auto-generated method stub
if (loginModel.isDBConnected()) {
db.setText("Connected to DATABASE");
} else {
db.setText("Not Connected");
}
}
public void Login (ActionEvent event ) {
try {
if (loginModel.isLogin(txtUsername.getText(), txtpassword.getText())) {
isConnected.setText("Correct");
try {
FXMLLoader addCustomer= new FXMLLoader(getClass().getResource("/sample/addcustomer.fxml"));
Parent root1 = (Parent)addCustomer.load();
Stage stage = new Stage();
stage.setScene(new Scene(root1));
stage.setTitle("ENTRY RECORD");
stage.show();
}
catch (Exception e){
e.printStackTrace();
}
} else {
Alert alert=new Alert(Alert.AlertType.ERROR);
alert.setHeaderText(null);
alert.setContentText("YOU ARE NOT AUTHENTICATED");
alert.show();
}
} catch (SQLException e) {
isConnected.setText("Incorrect");
e.printStackTrace();
}
}
}
COntroller类的FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.PasswordField?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.text.Font?>
<AnchorPane prefHeight="335.0" prefWidth="526.0" xmlns="http://javafx.com/javafx/8.0.121" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.Controller">
<children>
<Label id="isConnected" fx:id="isConnected" layoutX="69.0" layoutY="27.0" prefHeight="45.0" prefWidth="165.0" textAlignment="CENTER" textFill="#e81313">
<font>
<Font size="15.0" />
</font></Label>
<TextField fx:id="txtUsername" accessibleRole="MENU" layoutX="152.0" layoutY="124.0" promptText="Username" />
<Button fx:id="abutton" layoutX="201.0" layoutY="227.0" mnemonicParsing="false" onAction="#Login" text="Login" />
<PasswordField fx:id="txtpassword" layoutX="152.0" layoutY="154.0" promptText="Password" />
<Label fx:id="db" layoutX="247.0" layoutY="41.0" text="status">
<font>
<Font size="15.0" />
</font>
</Label>
</children>
</AnchorPane>
我的AddCustomer类 在这里，我还没有添加取消按钮的功能，只是想先检查“保存”按钮。
package sample;
import com.sun.istack.internal.NotNull;
import com.sun.istack.internal.Nullable;
import com.sun.org.apache.bcel.internal.generic.RETURN;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Alert;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
public class AddCustomer {
@FXML
public TextField number;
@FXML
public TextField name;
@FXML
public TextField stay;
@FXML
public TextField noofguests;
@FXML
public Button savebutton;
@FXML
public Button cancelbutton;
@FXML
@NotNull
@Nullable
public void addcustomer(ActionEvent actionEvent) throws Exception {
String customername = name.getText();
String customernumber = number.getText();
String customerstay = stay.getText();
String customerguests = noofguests.getText();
if (customername.isEmpty() || customerguests.isEmpty() || customernumber.isEmpty() || customerstay.isEmpty()) {
Alert alert = new Alert(Alert.AlertType.ERROR);
alert.setHeaderText(null);
alert.setContentText("PLEASE ENTER ALL THE FIELDS");
alert.show();
return;
}
String qu = "INSERT INTO CustomerDetails VALUES(" + "'" + customername + "'," +
"'" + customernumber + "'," +
"'" + customerstay + "'," +
"'" + customerguests + "'" + ")";
System.out.println(qu);
@NotNull
@Nullable
MysqlConnector mysqlConnector=new MysqlConnector();
try {
if (mysqlConnector.executeAction(qu)) {
@NotNull
@Nullable
Alert alert = new Alert(Alert.AlertType.INFORMATION);
alert.setHeaderText(null);
alert.setContentText("SUCCESS");
alert.show();
} else {
@NotNull
@Nullable
Alert alert = new Alert(Alert.AlertType.ERROR);
alert.setHeaderText(null);
alert.setContentText("FAILED");
alert.show();
}
}
catch(Exception e)
{ e.printStackTrace();}
}
public void cancel(ActionEvent actionEvent) {
}
}
我的添加客户FXML
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.geometry.Insets?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.TextField?>
<?import javafx.scene.layout.AnchorPane?>
<?import javafx.scene.layout.VBox?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="599.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="sample.AddCustomer">
<children>
<VBox layoutX="44.0" prefHeight="400.0" prefWidth="513.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="44.0" AnchorPane.rightAnchor="43.0" AnchorPane.topAnchor="0.0">
<children>
<TextField fx:id="name" prefHeight="50.0" prefWidth="492.0" promptText="Customer Name">
<VBox.margin>
<Insets bottom="10.0" left="10.0" right="10.0" top="30.0" />
</VBox.margin>
</TextField>
<TextField fx:id="number" layoutX="10.0" layoutY="10.0" prefHeight="53.0" prefWidth="492.0" promptText="Customer Number">
<VBox.margin>
<Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
</VBox.margin>
</TextField>
<TextField fx:id="stay" layoutX="10.0" layoutY="10.0" prefHeight="52.0" prefWidth="492.0" promptText="Stay Period ">
<VBox.margin>
<Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
</VBox.margin>
</TextField>
<TextField fx:id="noofguests" layoutX="10.0" layoutY="35.0" prefHeight="50.0" prefWidth="492.0" promptText="No. Of Guests">
<VBox.margin>
<Insets bottom="10.0" left="10.0" right="10.0" top="10.0" />
</VBox.margin>
</TextField>
<Button fx:id="savebutton" mnemonicParsing="false" onAction="#addcustomer" prefHeight="47.0" prefWidth="109.0" text="Save">
<VBox.margin>
<Insets bottom="10.0" left="100.0" right="10.0" top="10.0" />
</VBox.margin>
</Button>
<Button fx:id="cancelbutton" mnemonicParsing="false" onAction="#cancel" prefHeight="46.0" prefWidth="110.0" text="Cancel">
<VBox.margin>
<Insets bottom="10.0" left="300.0" right="10.0" top="-57.0" />
</VBox.margin>
</Button>
</children>
</VBox>
</children>
</AnchorPane>
请帮助解决此错误。
答案 0 :(得分：1)
出现此错误的原因是，您尝试在从未初始化的conn.createStatement();上调用conn上的null。
我看到您有一个名为Connector()的函数，它将初始化变量conn，但您从未调用过，一种解决方法是在{{1 }}，然后再尝试对变量Connector()进行任何操作。
MysqlConnector