EDIT

Errors are now handled by standard error handling, so we can probably close this ticket.

However, when I tried to delete a taxon node which I did delete before in the database (via SQL) I still got an exception which was difficult to read/understand by the user:

An error occurred while executing Delete. null
Please contact EDIT Support ....

Reason:
org.exclipse.core.commands.ExecutionException: While executing the operation, an exception occurred.

with stacktrace:

login : admin
editor version : 3.8.0.201509052203
server : localhost / Z350_editor_test
schema version : 3.6.0.0.201527040000
os : Windows Server 2012 6.2 amd64
java : 1.7.0_75
org.eclipse.core.commands.ExecutionException: While executing the operation, an exception occurred
    at org.eclipse.core.commands.operations.DefaultOperationHistory.execute(DefaultOperationHistory.java:521)
    at eu.etaxonomy.taxeditor.model.AbstractUtility$1.run(AbstractUtility.java:313)
    at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:464)
    at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:372)
    at org.eclipse.jface.window.ApplicationWindow$1.run(ApplicationWindow.java:759)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.jface.window.ApplicationWindow.run(ApplicationWindow.java:756)
    at org.eclipse.ui.internal.WorkbenchWindow.run(WorkbenchWindow.java:2649)
    at org.eclipse.ui.internal.progress.ProgressManager$RunnableWithStatus.run(ProgressManager.java:1346)
    at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
    at org.eclipse.ui.internal.progress.ProgressManager$7.run(ProgressManager.java:1184)
    at org.eclipse.swt.widgets.Synchronizer.syncExec(Synchronizer.java:180)
    at org.eclipse.ui.internal.UISynchronizer.syncExec(UISynchronizer.java:150)
    at org.eclipse.swt.widgets.Display.syncExec(Display.java:4683)
    at org.eclipse.ui.internal.progress.ProgressManager.runInUI(ProgressManager.java:1182)
    at eu.etaxonomy.taxeditor.model.AbstractUtility.runInUI(AbstractUtility.java:491)
    at eu.etaxonomy.taxeditor.model.AbstractUtility.executeOperation(AbstractUtility.java:331)
    at eu.etaxonomy.taxeditor.navigation.navigator.handler.DeleteHandler.execute(DeleteHandler.java:141)
    at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:293)
    at org.eclipse.core.commands.Command.executeWithChecks(Command.java:476)
    at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:508)
    at org.eclipse.ui.internal.handlers.HandlerService.executeCommand(HandlerService.java:169)
    at org.eclipse.ui.internal.handlers.SlaveHandlerService.executeCommand(SlaveHandlerService.java:241)
    at org.eclipse.ui.internal.handlers.SlaveHandlerService.executeCommand(SlaveHandlerService.java:241)
    at org.eclipse.ui.menus.CommandContributionItem.handleWidgetSelection(CommandContributionItem.java:829)
    at org.eclipse.ui.menus.CommandContributionItem.access$19(CommandContributionItem.java:815)
    at org.eclipse.ui.menus.CommandContributionItem$5.handleEvent(CommandContributionItem.java:805)
    at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
    at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1053)
    at org.eclipse.swt.widgets.Display.runDeferredEvents(Display.java:4165)
    at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3754)
    at org.eclipse.ui.internal.Workbench.runEventLoop(Workbench.java:2701)
    at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2665)
    at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499)
    at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679)
    at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
    at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668)
    at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
    at eu.etaxonomy.taxeditor.Application.start(Application.java:24)
    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(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    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)
Caused by: org.springframework.dao.InvalidDataAccessApiUsageException: deleted object would be re-saved by cascade (remove deleted object from associations): [eu.etaxonomy.cdm.model.taxon.Taxon#60]; nested exception is org.hibernate.ObjectDeletedException: deleted object would be re-saved by cascade (remove deleted object from associations): [eu.etaxonomy.cdm.model.taxon.Taxon#60]
    at org.springframework.orm.hibernate4.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:169)
    at org.springframework.orm.hibernate4.HibernateTransactionManager.convertHibernateAccessException(HibernateTransactionManager.java:680)
    at org.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:562)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:755)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:724)
    at eu.etaxonomy.cdm.api.conversation.ConversationHolder.commit(ConversationHolder.java:303)
    at eu.etaxonomy.taxeditor.operation.AbstractPersistentPostOperation.postExecute(AbstractPersistentPostOperation.java:99)
    at eu.etaxonomy.taxeditor.navigation.navigator.operation.DeleteOperation.execute(DeleteOperation.java:161)
    at org.eclipse.core.commands.operations.DefaultOperationHistory.execute(DefaultOperationHistory.java:513)
    ... 50 more
Caused by: org.hibernate.ObjectDeletedException: deleted object would be re-saved by cascade (remove deleted object from associations): [eu.etaxonomy.cdm.model.taxon.Taxon#60]
    at org.hibernate.internal.SessionImpl.forceFlush(SessionImpl.java:1225)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:182)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.performSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:114)
    at org.hibernate.event.internal.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:90)
    at org.hibernate.internal.SessionImpl.fireSaveOrUpdate(SessionImpl.java:727)
    at org.hibernate.internal.SessionImpl.saveOrUpdate(SessionImpl.java:719)
    at org.hibernate.engine.spi.CascadingAction$5.cascade(CascadingAction.java:258)
    at org.hibernate.engine.internal.Cascade.cascadeToOne(Cascade.java:387)
    at org.hibernate.engine.internal.Cascade.cascadeAssociation(Cascade.java:330)
    at org.hibernate.engine.internal.Cascade.cascadeProperty(Cascade.java:208)
    at org.hibernate.engine.internal.Cascade.cascade(Cascade.java:165)
    at org.hibernate.event.internal.AbstractFlushingEventListener.cascadeOnFlush(AbstractFlushingEventListener.java:160)
    at org.hibernate.event.internal.AbstractFlushingEventListener.prepareEntityFlushes(AbstractFlushingEventListener.java:151)
    at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:88)
    at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:51)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1213)
    at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:402)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:175)
    at org.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:554)
    ... 56 more

This is problamatic in multiple ways:

• The first sentence is not good English. If this is due to concatenation we should rather have a line break I guess. NPEs should always be translated to what it is and not using "null".

• Unexpected exceptions/errors should always be called "unexpected" not only exceptions/errors. If not execpected they should give more detailed information on what happened and how to solve it.

• We may want to check why a re-save may take place here. Though the data is corrupt in a way, I wouldn't expect resave to happen. But we may also check if this is the same behavior in remoting before spending unnecessary time here.

This ticket was split from #5140