突然间，我无法使用eclipse将动态Web项目导出到war文件。导出war时我得到空指针异常。这是异常的堆栈跟踪：
org.eclipse.core.commands.ExecutionException: Error exportingC:/Program Files (x86)/Apache Software/apache-tomcat-8.0.22/webapps/ShoppingService.war
at org.eclipse.jst.j2ee.internal.archive.operations.ComponentExportOperation.execute(ComponentExportOperation.java:150)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl$1.run(DataModelPausibleOperationImpl.java:385)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2313)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl.runOperation(DataModelPausibleOperationImpl.java:410)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl.runOperation(DataModelPausibleOperationImpl.java:360)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl.doExecute(DataModelPausibleOperationImpl.java:247)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl.executeImpl(DataModelPausibleOperationImpl.java:219)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl.cacheThreadAndContinue(DataModelPausibleOperationImpl.java:89)
at org.eclipse.wst.common.frameworks.internal.datamodel.DataModelPausibleOperationImpl.execute(DataModelPausibleOperationImpl.java:207)
at org.eclipse.wst.common.frameworks.internal.datamodel.ui.DataModelWizard$1CatchThrowableRunnableWithProgress.run(DataModelWizard.java:220)
at org.eclipse.jface.operation.ModalContext$ModalContextThread.run(ModalContext.java:122)
Caused by: java.lang.NullPointerException
at org.eclipse.jst.j2ee.internal.archive.operations.JavaEEComponentExportOperation.getModuleParticipants(JavaEEComponentExportOperation.java:75)
at org.eclipse.jst.j2ee.internal.archive.operations.JavaEEComponentExportOperation.getParticipants(JavaEEComponentExportOperation.java:43)
at org.eclipse.jst.j2ee.internal.archive.operations.JavaEEComponentExportOperation.createFlatComponentArchiver(JavaEEComponentExportOperation.java:91)
at org.eclipse.jst.j2ee.internal.archive.operations.ComponentExportOperation.export(ComponentExportOperation.java:191)
at org.eclipse.jst.j2ee.internal.archive.operations.ComponentExportOperation.execute(ComponentExportOperation.java:136)
... 10 more
有关发生了什么的任何想法？