eclipse - org.eclipse.e4.core.di.InjectionException : java. lang.NullPointerException

Question

这就是问题所在。我使用向导创建了一个示例 Eclipse 4 (Luna) 应用程序。一切正常。我决定将用户界面移至专用插件。我创建了新插件，将所有类移至新插件，并重构了 Eclipse 应用程序模型、产品和插件配置。现在，当我尝试启动 Eclipse 产品时，我得到了这个依赖注入(inject)异常。当我调试时，我注意到所有 UI 组件变量都有空值:

package my.company.ui.parts;

import javax.annotation.PostConstruct;
import javax.inject.Inject;

import org.eclipse.e4.ui.di.Focus;
import org.eclipse.e4.ui.di.Persist;
import org.eclipse.e4.ui.model.application.ui.MDirtyable;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.events.ModifyEvent;
import org.eclipse.swt.events.ModifyListener;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Text;

public class SamplePart {

    private Text txtInput;
    private TableViewer tableViewer;

    @Inject
    private MDirtyable dirty;

    @PostConstruct
    public void createComposite(Composite parent) {
        parent.setLayout(new GridLayout(1, false));

        txtInput = new Text(parent, SWT.BORDER);
        txtInput.setMessage("Enter text to mark part as dirty");
        txtInput.addModifyListener(new ModifyListener() {
            @Override
            public void modifyText(ModifyEvent e) {
                dirty.setDirty(true);
            }
        });
        txtInput.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));

        tableViewer = new TableViewer(parent);

        tableViewer.add("Sample item 1");
        tableViewer.add("Sample item 2");
        tableViewer.add("Sample item 3");
        tableViewer.add("Sample item 4");
        tableViewer.add("Sample item 5");
        tableViewer.getTable().setLayoutData(new GridData(GridData.FILL_BOTH));
    }

    @Focus
    public void setFocus() {
        tableViewer.getTable().setFocus();
    }

    @Persist
    public void save() {
        dirty.setDirty(false);
    }
}

抛出异常 setFocus()方法因为 tableViewer 的值变量为空。这是堆栈跟踪:

!ENTRY org.eclipse.e4.ui.workbench 4 0 2014-07-10 16:40:26.368
!MESSAGE Failed to grant focus to element
!STACK 0
org.eclipse.e4.core.di.InjectionException: java.lang.NullPointerException
    at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:62)
    at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:247)
    at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:225)
    at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:107)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.focusGui(PartRenderingEngine.java:795)
    at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.activate(PartServiceImpl.java:679)
    at org.eclipse.e4.ui.internal.workbench.PartServiceImpl.switchPerspective(PartServiceImpl.java:572)
    at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.showTab(PerspectiveStackRenderer.java:127)
    at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer$1.handleEvent(LazyStackRenderer.java:66)
    at org.eclipse.e4.ui.services.internal.events.UIEventHandler$1.run(UIEventHandler.java:40)
    at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:187)
    at org.eclipse.swt.widgets.Display.syncExec(Display.java:4734)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application$1.syncExec(E4Application.java:218)
    at org.eclipse.e4.ui.services.internal.events.UIEventHandler.handleEvent(UIEventHandler.java:36)
    at org.eclipse.equinox.internal.event.EventHandlerWrapper.handleEvent(EventHandlerWrapper.java:197)
    at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:197)
    at org.eclipse.equinox.internal.event.EventHandlerTracker.dispatchEvent(EventHandlerTracker.java:1)
    at org.eclipse.osgi.framework.eventmgr.EventManager.dispatchEvent(EventManager.java:230)
    at org.eclipse.osgi.framework.eventmgr.ListenerQueue.dispatchEventSynchronous(ListenerQueue.java:148)
    at org.eclipse.equinox.internal.event.EventAdminImpl.dispatchEvent(EventAdminImpl.java:135)
    at org.eclipse.equinox.internal.event.EventAdminImpl.sendEvent(EventAdminImpl.java:78)
    at org.eclipse.equinox.internal.event.EventComponent.sendEvent(EventComponent.java:39)
    at org.eclipse.e4.ui.services.internal.events.EventBroker.send(EventBroker.java:81)
    at org.eclipse.e4.ui.internal.workbench.UIEventPublisher.notifyChanged(UIEventPublisher.java:59)
    at org.eclipse.emf.common.notify.impl.BasicNotifierImpl.eNotify(BasicNotifierImpl.java:374)
    at org.eclipse.e4.ui.model.application.ui.advanced.impl.PerspectiveStackImpl.setSelectedElement(PerspectiveStackImpl.java:135)
    at org.eclipse.e4.ui.model.application.ui.advanced.impl.PerspectiveStackImpl.setSelectedElement(PerspectiveStackImpl.java:1)
    at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer.postProcess(LazyStackRenderer.java:103)
    at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.postProcess(PerspectiveStackRenderer.java:77)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:678)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
    at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:68)
    at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.processContents(WBWRenderer.java:664)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:674)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:766)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:737)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:731)
    at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:715)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1074)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1032)
    at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:148)
    at org.eclipse.e4.ui.internal.workbench.swt.E4Application.start(E4Application.java:164)
    at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
    at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:382)
    at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:236)
    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:483)
    at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:648)
    at org.eclipse.equinox.launcher.Main.basicRun(Main.java:603)
    at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
    at org.eclipse.equinox.launcher.Main.main(Main.java:1438)
Caused by: java.lang.NullPointerException
    at com.boeing.ccts.mpa.workbench.planner.ui.parts.SamplePart.setFocus(SamplePart.java:52)
    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:483)
    at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:55)
    ... 60 more

我在另一篇文章中阅读了与注释有关的文章，这也导致人们相信这是一个依赖注入(inject)问题。不知道如何修复它。任何帮助，将不胜感激。

Answer 1

检查您是否有不同版本的 javax.annotation运行。您可以使用 OSGi 控制台和命令 packages javax.annotation来验证这是否成立。我曾经遇到过与您看到的类似效果的问题:两个包使用不同版本的注释，因此一个包无法识别另一个包中使用的注释，因为不同的包具有不同的类加载器。