init 方法中的异常 - JavaFX

使用 eclipse 导出到 .jar 文件后出现此异常。 IntelliJ 也这么说。但我的程序在 eclipse 中运行良好。

Exception in thread "main" java.lang.NoClassDefFoundError: javafx/application/Application
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.launcher.LauncherHelper.checkAndLoadMain(Unknown Source)

Caused by: java.lang.ClassNotFoundException: javafx.application.Application
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 13 more

这可能是怎么回事？

JDK版本：1.7.0_79 开始：java -jar myapp.jar

使用 java -cp jfxrt.jar -jar myapp.jar 尝试后，出现以下错误：

java -cp jfxrt.jar -jar memo.jar
Exception in thread "JavaFX Application Thread" Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/log4j/Layout
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at com.sun.javafx.application.LauncherImpl.lambda$launchApplicationWithArgs$100(LauncherImpl.java:352)
    at com.sun.javafx.application.PlatformImpl.lambda$runAndWait$119(PlatformImpl.java:326)
    at com.sun.javafx.application.PlatformImpl.lambda$null$117(PlatformImpl.java:295)
    at java.security.AccessController.doPrivileged(Native Method)
    at com.sun.javafx.application.PlatformImpl.lambda$runLater$118(PlatformImpl.java:294)
    at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
    at com.sun.glass.ui.gtk.GtkApplication._runLoop(Native Method)
    at com.sun.glass.ui.gtk.GtkApplication.lambda$null$450(GtkApplication.java:139)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.ClassNotFoundException: org.apache.log4j.Layout
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 11 more
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.launcher.LauncherHelper$FXHelper.main(LauncherHelper.java:767)
Caused by: java.lang.NullPointerException
    at com.sun.javafx.application.LauncherImpl.launchApplicationWithArgs(LauncherImpl.java:383)
    at com.sun.javafx.application.LauncherImpl.launchApplication(LauncherImpl.java:328)
    ... 5 more

javafx.application.Application 类可以在 javafx 库中找到；在 Eclipse 等 IDE 中，您通常会配置项目来引用编译和执行所需的库。当您将代码放入 jar 并在 IDE 外部运行时，您需要以不同的方式向运行时提供库。

执行此操作的标准方法是设置一个类路径，该路径引用应用程序 jar 及其所需的任何库；执行此操作的 DOS 命令如下所示：

set classpath=c:\myProjects\myApplication\myJar.jar;c:\java\libaries\javafx\jfxrt.jar

然后java就可以访问这两个jar文件中的类