javafx jar 不会运行，找不到主类

Question

我知道这个问题已经被问过很多次了，但没有一个解决方案对我有用。我正在使用 gradle 为 javafx 应用程序构建一个可运行的 jar。我正在使用 Java 8 jdk 和 jre。当我用 7zip 打开 jar 时，我看到它包含了我的类路径。

这是我的文件：

build.gradle

plugins {
    id 'java'
    id 'edu.sc.seis.launch4j' version '2.4.9'
    id 'application'
}

application {
    mainClass = 'sample.Main'
}

jar {
    manifest {
        attributes (
                'Main-Class': 'sample.Main',
                "Class-Path": configurations.compile.collect { it.getName() }.join(' '))
    }
}

launch4j {
    outfile = 'MortgageCalculator.exe'
    mainClassName = 'sample.Main'
}

Main.java

package sample;

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("sample.fxml"));
        primaryStage.setTitle("Maximum House Bid Calculator");
        primaryStage.setScene(new Scene(root));
        primaryStage.show();
    }


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

项目结构

来自 build/libs 的 jar 内容

尝试运行 jar 时的输出

从命令行使用gradle run的输出

D:\dev\repos\java\MortageBidCalculator>gradle run

> Task :run FAILED
Exception in Application start method
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$1(LauncherImpl.java:182)
        at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NullPointerException: Location is required.
        at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3207)
        at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3175)
        at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3148)
        at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3124)
        at javafx.fxml.FXMLLoader.loadImpl(FXMLLoader.java:3104)
        at javafx.fxml.FXMLLoader.load(FXMLLoader.java:3097)
        at sample.Main.start(Main.java:13)
        at com.sun.javafx.application.LauncherImpl.lambda$launchApplication1$8(LauncherImpl.java:863)
        at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$7(PlatformImpl.java:326)
        at com.sun.javafx.application.PlatformImpl.lambda$null$5(PlatformImpl.java:295)
        at java.security.AccessController.doPrivileged(Native Method)
        at com.sun.javafx.application.PlatformImpl.lambda$runLater$6(PlatformImpl.java:294)
        at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
        at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
        at com.sun.glass.ui.win.WinApplication.lambda$null$4(WinApplication.java:186)
        ... 1 more
Exception running application sample.Main

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':run'.
> Process 'command 'C:\Program Files\Java\jdk1.8.0_251\bin\java.exe'' finished with non-zero exit value 1

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights.

* Get more help at https://help.gradle.org

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.8/userguide/command_line_interface.html#sec:command_line_warnings

BUILD FAILED in 4s
2 actionable tasks: 1 executed, 1 up-to-date

我认为 gradle run 错误只是因为它没有找到 fxml 文件，所以我很确定这与 no main class found 错误无关，但我不完全确定。

Answer 1

要从命令行运行 jar 文件，您需要 -jar 选项：

java -jar MortgageBidCalculator.jar

导致空指针异常的另一个问题是FXML文件不在jar文件中。

在src/main下创建resources文件夹，sample子文件夹，并将sample.fxml移动到src/main/resources/sample。