JavaFX Exception in Application start method when executed with Spring Boot Code Answer

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I have created a simple javaFX program and i added spring boot to javaFX by making the project a maven project. Before adding spring boot i got no error and the application worked fine. I have provided the complete code below

pom.xml

    <?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.6.RELEASE</version>
    </parent>
    <groupId>groupId</groupId>
    <artifactId>RMI-DesktopClient</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>  
</project>

AlarmsystemApplication.java

    @Configuration
@SpringBootApplication
public class AlarmSystemApplication extends Application {

    private ConfigurableApplicationContext applicationContext;

    @Override
    public void init() throws Exception {
        this.applicationContext = SpringApplication.run(AlarmSystemApplication.class);

    }
    @Override
    public void stop() throws Exception {
        applicationContext.close();
    }

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

    @Override
    public void start(Stage stage) throws Exception {
        Login.loadView(stage);
    }
}

Login.java

  public class Login {
    public static void loadView(Stage stage) {

        try {
            Parent view = FXMLLoader.load(Login.class.getResource("../../../../../resources/com.ui.views/Login.fxml"));
            stage.setScene(new Scene(view));
            stage.show();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Login.fxml

    <AnchorPane prefHeight="400.0" prefWidth="600.0" xmlns="http://javafx.com/javafx/8.0.171" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.alarmsystem.ui.views.Login">
   <children>
      <Label layoutX="137.0" layoutY="157.0" text="Hello JavaFX">
         <font>
            <Font size="59.0" />
         </font>
      </Label>
   </children>
</AnchorPane>

The error that i get

    Exception in Application start method
2020-04-23 22:33:12.134  INFO 7228 --- [lication Thread] j.LocalContainerEntityManagerFactoryBean : Closing JPA EntityManagerFactory for persistence unit 'default'
2020-04-23 22:33:12.136  INFO 7228 --- [lication Thread] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown initiated...
2020-04-23 22:33:12.139  INFO 7228 --- [lication Thread] com.zaxxer.hikari.HikariDataSource       : HikariPool-1 - Shutdown completed.
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 com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:389)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    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.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.RuntimeException: Exception in Application start method
    at com.sun.javafx.application.LauncherImpl.launchApplication1(LauncherImpl.java:917)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication$154(LauncherImpl.java:182)
    at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException: Location is required.
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
    at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
    at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
    at com.alarmsystem.ui.views.Login.loadView(Login.java:16)
    at com.alarmsystem.ui.AlarmSystemApplication.start(AlarmSystemApplication.java:34)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$161(LauncherImpl.java:863)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$174(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$172(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$173(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
    at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
    ... 1 more
Exception running application com.alarmsystem.ui.AlarmSystemApplication

Process finished with exit code 1

The file structure enter image description here

The resources path enter image description here

Answer

I’m not sure this is Spring related; the resource name you use for your FXML is not a valid resource name (and the stack trace indicates that not being able to find the FXML file is the issue).

Specifically, resource names cannot have . in them, so .. and com.ui.views are both invalid.

So there are two problems here: one is that the resources name doesn’t work with “parent directories” specified in it, and the other is that you have created a folder (not a package) under resources with illegal . characters in it. Also note that resources is a source folder, and is not available at runtime.

So, first, create a package under resources called com.ui.views and place the FMXL in there. I don’t use IntelliJ, so I’m not sure if there is an option to do this, but if not you can create a folder com, a subfolder of it called ui, and a subfolder of that called views, and place the FXML file in views.

Then the correct resource name for the FXML, assuming you are using Maven defaults for your build, is

Parent view = FXMLLoader.load(Login.class.getResource("/com/ui/views/Login.fxml"));

If you restructure slightly so that the FXML file and Login class are in the same package (i.e. you make a com.alarmsystem.ui.views package under resources), then you can just do

Parent view = FXMLLoader.load(Login.class.getResource("Login.fxml"));

If you need to troubleshoot further, you can see where the resources were deployed (so where they are found at runtime), by looking in the target/classes folder.

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