当应用程序作为Java Web Start运行时，为什么桌面API会抛出NPE？

我使用Java大约只有6个月的时间，所以我绝对是新手。另外，几天前我确实在Oracle技术网络社区上发布了此问题，但没有听到任何声音。

我正在开发的应用程序目前正在通过网络启动进行Beta测试。我们认为这是使用户了解最新错误修复的最佳方法。我想我应该提到这是一个使用Maven的JavaFX应用程序。在应用程序中，我正在使用Desktop API的OPEN和MAIL操作。OPEN操作用于打开系统文件夹浏览器。这是我需要采取的行动。MAIL操作更多是为了用户方便。从可执行jar运行应用程序时，两者都工作正常，但是当通过Web Start启动应用程序时，两者都得到了NPE。它通过了isDesktopSupported测试。一切均已通过经过验证的DigiCert证书签名，并设置了所有权限。当应用程序首次启动时，它将在用户主目录中毫无问题地创建一个文件夹和配置文件。

我创建了一个小型演示应用程序，以确保我的应用程序中没有其他地方引起此问题，但是我得到了完全相同的错误。我发布的代码来自演示应用程序。

FXMLController.java

import java.awt.Desktop;
import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.util.ResourceBundle;
import java.util.logging.Level;
import java.util.logging.Logger;
import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Button;
import javafx.scene.control.Hyperlink;

public class FXMLController implements Initializable {

    @FXML
    private Button button;
    @FXML
    private Hyperlink hyperlink;

    @FXML
    private void handleButtonAction(ActionEvent event) {
    if (Desktop.isDesktopSupported()) {
        if (Desktop.getDesktop().isSupported(Desktop.Action.OPEN)) { //NPE thrown here
        try {
            Desktop.getDesktop().open(new File(System.getProperty("user.home")));
        } catch (IOException ex) {
            Logger.getLogger(FXMLController.class.getName()).log(Level.SEVERE, null, ex);
        }
        } else {
        System.out.println("The OPEN action is not supported on your current platform.");
        }
    } else {
        System.out.println("The Desktop class is not supported on your current platform.");
    }
    }

    @FXML
    private void handleLinkAction(ActionEvent event) {
    if (Desktop.isDesktopSupported()) {
        if (Desktop.getDesktop().isSupported(Desktop.Action.MAIL)) { //NPE thrown here
        try {
            Desktop.getDesktop().mail(new URI("mailto:[email protected]"));
        } catch (IOException | URISyntaxException ex) {
            Logger.getLogger(FXMLController.class.getName()).log(Level.SEVERE, null, ex);
        }
        } else {
        System.out.println("The MAIL action is not supported on your current platform.");
        }
    } else {
        System.out.println("The Desktop class is not supported on your current platform.");
    }
    }

    @Override
    public void initialize(URL url, ResourceBundle rb) {
    }
}

JNLP文件

<?xml version="1.0" encoding="UTF-8"?>  
<jnlp spec="1.0+" xmlns:jfx="http://javafx.com" href="DesktopClassTesting.jnlp">  
    <information>  
  <title>DesktopClassTesting</title>  
  <vendor>USGS</vendor>  
    </information>  
    <security>  
  <all-permissions/>  
    </security>  
    <update check="always" policy="always" />  
    <resources>  
  <j2se version="1.7.0_60+" href="http://java.sun.com/products/autodl/j2se" />  
  <jar href="DesktopClassTesting.jar" main="true" version="0.1-SNAPSHOT"/>  
  <property name="jnlp.versionEnabled" value="true"/>  
    </resources>  
    <application-desc name="Desktop Class Testing"/>  
    <jfx:javafx-desc main-class="gov.usgs.tnm.desktopclasstesting.MainApp" name="MainApp"/>  
</jnlp>  

OPEN操作堆栈跟踪

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException  
  at javafx.fxml.FXMLLoader$MethodHandler.invoke(Unknown Source)  
  at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(Unknown Source)  
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)  
  at javafx.event.Event.fireEvent(Unknown Source)  
  at javafx.scene.Node.fireEvent(Unknown Source)  
  at javafx.scene.control.Button.fire(Unknown Source)  
  at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(Unknown Source)  
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)  
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)  
  at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)  
  at javafx.event.Event.fireEvent(Unknown Source)  
  at javafx.scene.Scene$MouseHandler.process(Unknown Source)  
  at javafx.scene.Scene$MouseHandler.access$1800(Unknown Source)  
  at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)  
  at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)  
  at java.security.AccessController.doPrivileged(Native Method)  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)  
  at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)  
  at com.sun.glass.ui.View.notifyMouse(Unknown Source)  
  at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)  
  at com.sun.glass.ui.win.WinApplication.access$300(Unknown Source)  
  at com.sun.glass.ui.win.WinApplication$4$1.run(Unknown Source)  
  at java.lang.Thread.run(Unknown Source)  
Caused by: java.lang.reflect.InvocationTargetException  
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)  
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)  
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
  at java.lang.reflect.Method.invoke(Unknown Source)  
  at sun.reflect.misc.Trampoline.invoke(Unknown Source)  
  at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)  
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
  at java.lang.reflect.Method.invoke(Unknown Source)  
  at sun.reflect.misc.MethodUtil.invoke(Unknown Source)  
  ... 48 more  
Caused by: java.lang.NullPointerException  
  at java.awt.Desktop.getDesktop(Unknown Source)  
  at gov.usgs.tnm.desktopclasstesting.FXMLController.handleButtonAction(FXMLController.java:30)  
  ... 57 more  

邮件操作stacktrace

Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException  
  at javafx.fxml.FXMLLoader$MethodHandler.invoke(Unknown Source)  
  at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(Unknown Source)  
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)  
  at javafx.event.Event.fireEvent(Unknown Source)  
  at javafx.scene.Node.fireEvent(Unknown Source)  
  at javafx.scene.control.Hyperlink.fire(Unknown Source)  
  at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(Unknown Source)  
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)  
  at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(Unknown Source)  
  at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEventImpl(Unknown Source)  
  at com.sun.javafx.event.EventUtil.fireEvent(Unknown Source)  
  at javafx.event.Event.fireEvent(Unknown Source)  
  at javafx.scene.Scene$MouseHandler.process(Unknown Source)  
  at javafx.scene.Scene$MouseHandler.access$1800(Unknown Source)  
  at javafx.scene.Scene.impl_processMouseEvent(Unknown Source)  
  at javafx.scene.Scene$ScenePeerListener.mouseEvent(Unknown Source)  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(Unknown Source)  
  at java.security.AccessController.doPrivileged(Native Method)  
  at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(Unknown Source)  
  at com.sun.glass.ui.View.handleMouseEvent(Unknown Source)  
  at com.sun.glass.ui.View.notifyMouse(Unknown Source)  
  at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)  
  at com.sun.glass.ui.win.WinApplication.access$300(Unknown Source)  
  at com.sun.glass.ui.win.WinApplication$4$1.run(Unknown Source)  
  at java.lang.Thread.run(Unknown Source)  
Caused by: java.lang.reflect.InvocationTargetException  
  at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)  
  at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)  
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
  at java.lang.reflect.Method.invoke(Unknown Source)  
  at sun.reflect.misc.Trampoline.invoke(Unknown Source)  
  at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)  
  at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)  
  at java.lang.reflect.Method.invoke(Unknown Source)  
  at sun.reflect.misc.MethodUtil.invoke(Unknown Source)  
  ... 48 more  
Caused by: java.lang.NullPointerException  
  at java.awt.Desktop.getDesktop(Unknown Source)  
  at gov.usgs.tnm.desktopclasstesting.FXMLController.handleLinkAction(FXMLController.java:51)  
  ... 57 more  

如果需要，我可以发布FXML文件和MainApp.java。我已经为此工作了几天，但都没有成功，因此任何见解都会很棒。谢谢。