java - Eclipse RCP 应用程序中的 NoClassDefFoundError

Question

在我们的应用程序中，我们有时(大约十分之一)得到 NoClassDefFoundError当尝试实例化一个类时。当没有我们的应用程序打开项目时，就会发生这种情况。

完整的堆栈跟踪如下所示:

!ENTRY org.eclipse.jface 4 2 2011-11-18 12:45:33.941
!MESSAGE Problems occurred when invoking code from plug-in: "org.eclipse.jface".
!STACK 0
java.lang.NoClassDefFoundError: com.mycompany.products.myapp.gui.model.provider.EMyAppObjectItemProvider
    at com.mycompany.products.myapp.gui.model.provider.MyappguimodelItemProviderAdapterFactory.createMyAppGuiPortAdapter(MyappguimodelItemProviderAdapterFactory.java:159)
    at com.mycompany.products.myapp.gui.model.util.MyappguimodelAdapterFactory$1.caseMyAppGuiPort(MyappguimodelAdapterFactory.java:185)
    at com.mycompany.products.myapp.gui.model.util.MyappguimodelAdapterFactory$1.caseMyAppGuiPort(MyappguimodelAdapterFactory.java:1)
    at com.mycompany.products.myapp.gui.model.util.MyappguimodelSwitch.doSwitch(MyappguimodelSwitch.java:226)
    at org.eclipse.emf.ecore.util.Switch.doSwitch(Switch.java:59)
    at org.eclipse.emf.ecore.util.Switch.doSwitch(Switch.java:75)
    at com.mycompany.products.myapp.gui.model.util.MyappguimodelAdapterFactory.createAdapter(MyappguimodelAdapterFactory.java:462)
    at org.eclipse.emf.common.notify.impl.AdapterFactoryImpl.createAdapter(AdapterFactoryImpl.java:133)
    at org.eclipse.emf.common.notify.impl.AdapterFactoryImpl.adaptNew(AdapterFactoryImpl.java:107)
    at org.eclipse.emf.common.notify.impl.AdapterFactoryImpl.adapt(AdapterFactoryImpl.java:93)
    at com.mycompany.products.myapp.gui.model.provider.MyappguimodelItemProviderAdapterFactory.adapt(MyappguimodelItemProviderAdapterFactory.java:1127)
    at org.eclipse.emf.edit.provider.ComposedAdapterFactory.adapt(ComposedAdapterFactory.java:300)
    at org.eclipse.emf.edit.provider.ComposedAdapterFactory.adapt(ComposedAdapterFactory.java:277)
    at org.eclipse.emf.edit.provider.ComposedAdapterFactory.adapt(ComposedAdapterFactory.java:264)
    at org.eclipse.emf.edit.ui.provider.AdapterFactoryLabelProvider.getColumnText(AdapterFactoryLabelProvider.java:496)
    at org.eclipse.jface.viewers.TableColumnViewerLabelProvider.update(TableColumnViewerLabelProvider.java:70)
    at org.eclipse.jface.viewers.ViewerColumn.refresh(ViewerColumn.java:152)
    at org.eclipse.jface.viewers.AbstractTableViewer.doUpdateItem(AbstractTableViewer.java:399)
    at org.eclipse.jface.viewers.StructuredViewer$UpdateItemSafeRunnable.run(StructuredViewer.java:485)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.ui.internal.JFaceUtil$1.run(JFaceUtil.java:49)
    at org.eclipse.jface.util.SafeRunnable.run(SafeRunnable.java:175)
    at org.eclipse.jface.viewers.StructuredViewer.updateItem(StructuredViewer.java:2167)
    at org.eclipse.jface.viewers.AbstractTableViewer.createItem(AbstractTableViewer.java:277)
    at org.eclipse.jface.viewers.AbstractTableViewer.internalRefreshAll(AbstractTableViewer.java:757)
    at org.eclipse.jface.viewers.AbstractTableViewer.internalRefresh(AbstractTableViewer.java:649)
    at org.eclipse.jface.viewers.AbstractTableViewer.internalRefresh(AbstractTableViewer.java:636)
    at org.eclipse.jface.viewers.AbstractTableViewer$2.run(AbstractTableViewer.java:592)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1443)
    at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1404)
    at org.eclipse.jface.viewers.AbstractTableViewer.inputChanged(AbstractTableViewer.java:590)
    at org.eclipse.jface.viewers.ContentViewer.setInput(ContentViewer.java:280)
    at org.eclipse.jface.viewers.StructuredViewer.setInput(StructuredViewer.java:1690)
    at com.mycompany.products.myapp.gui.views.port.composites.Ipv4PortComposite.projectOpenedOrClosed(Ipv4PortComposite.java:732)
    at com.mycompany.products.myapp.gui.project.MyAppResourceController.tellOpenCloseListeners(MyAppResourceController.java:186)
    at com.mycompany.products.myapp.gui.actions.project.MyAppGuiResourceController.openProject(MyAppGuiResourceController.java:266)
    at com.mycompany.products.myapp.gui.project.MyAppResourceController.open(MyAppResourceController.java:592)
    at com.mycompany.products.myapp.gui.project.MyAppResourceController.openWithoutUpdating(MyAppResourceController.java:612)
    at com.mycompany.products.myapp.gui.actions.file.MyAppRecentProjectAction.run(MyAppRecentProjectAction.java:55)
    at org.eclipse.jface.action.Action.runWithEvent(Action.java:498)
    at org.eclipse.jface.action.ActionContributionItem.handleWidgetSelection(ActionContributionItem.java:584)
        at org.eclipse.jface.action.ActionContributionItem.access$2(ActionContributionItem.java:501)
    at org.eclipse.jface.action.ActionContributionItem$5.handleEvent(ActionContributionItem.java:411)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1258)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:3588)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3209)
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2696)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2660)
    at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2494)
    at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:674)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:667)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at com.mycompany.products.myapp.gui.MyAppApplication.start(MyAppApplication.java:175)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:616)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1410)
    at org.eclipse.equinox.launcher.M

这些相关问题没有回答我的问题:

• NoClassDefFoundError on JFace FontRegistry
• Getting class not found Exception when running in eclipse

据我所知，当在运行时类路径中找不到该类时，就会发生此异常。因此，我认为如果我可以在实际尝试实例化之前打印运行时搜索路径，将会很有用。这样我就可以检查失败的 1/10 次是否有任何差异。但是，我还没有找到如何获取运行时搜索路径列表。关于如何获得它们有任何提示吗？

谁能帮我解决这个问题吗？

Answer 1

对于类加载问题，Java 提供了一些工具。看Do you really get class loaders在幻灯片共享上。我曾经在集成到我的 RCP 产品中的 Eclipse 帮助系统中遇到过类似的问题。当在 IDE 中启动时，一切工作正常，但是当启动导出的产品时，帮助系统就不会出现。