JavaFX：IntelliJ IDEA 工件抛出 NullPointerException答案

【问题标题】：JavaFX: IntelliJ IDEA Artifacts throws NullPointerExceptionJavaFX：IntelliJ IDEA 工件抛出 NullPointerException
【发布时间】：2019-05-22 15:47:21
【问题描述】：

我正在开发一个 JavaFX 项目。该程序通过 IntelliJ IDEA 运行时按预期工作。但是，当我创建一个工件并运行 jar 文件时，我会看到登录屏幕，但只要我点击登录按钮，应用程序就会崩溃并引发错误。

我通过终端以某种方式追踪了错误。

我的代码如下。

Main.java：

package application;

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("/FXML/Login.fxml"));
        primaryStage.setTitle("Pelican Tours - Login");
        primaryStage.setScene(new Scene(root, 311, 429));
        primaryStage.show();
        primaryStage.setResizable(false);
    }


    public static void main(String[] args) {
        launch(args);
    }
}

这会调用 Login.fxml，然后调用 LoginController.java：

package Controllers;

import DBConnection.DBHandler;
import application.Main;
import com.jfoenix.controls.JFXButton;
import com.jfoenix.controls.JFXPasswordField;
import com.jfoenix.controls.JFXTextField;
import javafx.fxml.FXML;
import javafx.fxml.FXMLLoader;
import javafx.fxml.Initializable;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.control.Alert;
import javafx.stage.Stage;

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.io.IOException;
import java.net.URL;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ResourceBundle;

public class LoginController implements Initializable {

    @FXML
    private JFXTextField username;

    @FXML
    private JFXPasswordField password;

    @FXML
    private JFXButton login;

    private Connection conn;
    private DBHandler handler;
    private PreparedStatement pst;



    @Override
    public void initialize(URL location, ResourceBundle resources) {
        handler = new DBHandler();
        username.setStyle("-fx-text-inner-color:#a0a2ab;");
        password.setStyle("-fx-text-inner-color:#a0a2ab;");
    }


    @FXML
    public void logon() {

        conn = handler.getConnection();
        String query1 = "SELECT * FROM USER WHERE USERNAME=? AND PASSWORD=?";

        try{
            pst = conn.prepareStatement(query1);
            pst.setString(1,username.getText());
            pst.setString(2,password.getText());
            ResultSet rs = pst.executeQuery();

            //Validate resultset
            int count = 0;
            while(rs.next()){
                count++;
            }
            if(count==1){
                System.out.println("Login Successful!");
                login.getScene().getWindow().hide();
                Stage dashboard = new Stage();
                try{
                    Parent root = FXMLLoader.load(getClass().getResource("/FXML/Dashboard.fxml"));
                    Scene scene = new Scene(root);
                    dashboard.setScene(scene);
                    dashboard.show();
                    dashboard.setResizable(false);
                }catch(Exception e){
                    System.out.println("Error loading dashboard!");
                    System.out.println(e);
                    e.printStackTrace();
                }
            }else{
                Alert alert = new Alert(Alert.AlertType.ERROR);
                alert.setHeaderText("Login Failed!");
                alert.setContentText("Invalid Username & Password Combination!");
                alert.show();
            }

        }catch(SQLException e){
            e.printStackTrace();
        }finally{
            try{
                handler.closeConnection();
            }catch(SQLException e){
                e.printStackTrace();
            }
        }
    }

}

当调用“登录”操作时，它应该加载仪表板。但是，应用程序只是崩溃了。

我首先打印了异常，然后打印了它的堆栈跟踪。：

Connected!
Login Successful!
Error loading dashboard!
java.lang.NullPointerException: Location is required.
java.lang.NullPointerException: Location is required.
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at Controllers.LoginController.logon(LoginController.java:75)
    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$MethodHandler.invoke(FXMLLoader.java:1771)
    at javafx.fxml.FXMLLoader$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$MouseEventNotification.run(GlassViewEventHandler.java:381)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$354(GlassViewEventHandler.java:417)
    at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
    at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:416)
    at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
    at com.sun.glass.ui.View.notifyMouse(View.java:937)

据我了解，“java.lang.NullPointerException：需要位置”。是由于.getResource()中的路径错误引起的。

但是，我在上面发布的 Main.java 类中的相同路径格式可以正常工作。（这就是我获得登录屏幕的方式）。

文件夹结构如下：

Folder Structure

**请注意：** 该程序在 IDE 中完美运行。此错误仅在运行 .jar 文件时发生。

提前谢谢你！

【问题讨论】：

检查 JAR 文件以确保在构建时将 FXML 文件添加到其中。

标签： java intellij-idea javafx jar artifacts

【解决方案1】：

是的。它的发生是因为路径是错误的。尝试使用 winrar 或类似的工具打开 jar 文件。然后尝试找到您尝试在 getResource 中传递的文件。然后尝试将该路径放在 jar 内的位置，并在编译后再次检查运行 jar

【讨论】：

【解决方案2】：

谢谢。我设法通过将整个项目文件夹设置为“源根”来解决它。（右键项目 --> Mark Directory as --> Source Root）

【讨论】：