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Re: Setting up horizontal inheritance
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Re: Setting up horizontal inheritance

  • Subject: Re: Setting up horizontal inheritance
  • From: Paul Hoadley <email@hidden>
  • Date: Mon, 3 Nov 2008 15:48:53 +1030
I'm sure I'm close to understanding this... thanks for bearing with me.

On 03/11/2008, at 1:19 PM, Ken Anderson wrote:

On Nov 1, 2008, at 10:51 PM, Paul Hoadley wrote:

I've implemented it using HI, and it seems to be working.  I'm not convinced I have it quite right, though.  There's another EO in the utility-framework's model, UserPreference.  UserPreference has a to-one relationship with Person to denote the owner of the preference.  In the particular app, though, I'm now using AMPersons, and hence the amperson table in the database---but UserPreference.person relationship obviously looks for a Person in the 'person' table, and there aren't any.  To overcome this, I have sub-classed UserPreference to create AMUserPreference, with the only change being that the person relationship points to AMPerson.  This seems inelegant to me---am I doing it right?  (Or is this a candidate for the kind of dynamic model change you refer to above?)

This is why it would be better for Person to be abstract, and have different subentities for each application.  That way, UserPreference could have a relationship to the abstract Person entity, which would automatically search all the subentities for the correct one for that particular primary key.

I've made Person abstract in the model.  I've deleted the redundant EO (AMUserPreference), and UserPreference (which is in the same framework as Person) points to the abstract Person entity.  I no longer generate a 'person' table, as I won't be instantiating Person.  Now, where the app would create a UserPreference, I get this on saving:

[2008-11-3 15:33:36 CST] <WorkerThread0> <com.webobjects.appserver._private.WOComponentRequestHandler>: Exception occurred while handling request:
java.lang.NullPointerException
Application.handleException: Handling an Exception:
java.lang.NullPointerException
at com.webobjects.eoaccess.EODatabaseContext._verifyNoChangesToReadonlyEntity(EODatabaseContext.java:4696)
at com.webobjects.eoaccess.EODatabaseContext.performChanges(EODatabaseContext.java:6183)
at com.webobjects.eocontrol.EOObjectStoreCoordinator.saveChangesInEditingContext(EOObjectStoreCoordinator.java:376)
at com.webobjects.eocontrol.EOEditingContext.saveChanges(EOEditingContext.java:3176)
at net.logicsquad.am.components.pages.UserPreferencesPage.saveButtonAction(UserPreferencesPage.java:23)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at com.webobjects.foundation.NSKeyValueCoding$ValueAccessor$1.methodValue(NSKeyValueCoding.java:636)
at com.webobjects.foundation.NSKeyValueCoding$_MethodBinding.valueInObject(NSKeyValueCoding.java:1134)
at com.webobjects.foundation.NSKeyValueCoding$DefaultImplementation.valueForKey(NSKeyValueCoding.java:1293)
at com.webobjects.appserver.WOComponent.valueForKey(WOComponent.java:1686)
at com.webobjects.foundation.NSKeyValueCoding$Utility.valueForKey(NSKeyValueCoding.java:447)
at com.webobjects.foundation.NSKeyValueCodingAdditions$DefaultImplementation.valueForKeyPath(NSKeyValueCodingAdditions.java:212)
at net.logicsquad.am.AMComponent.valueForKeyPath(AMComponent.java:153)
at com.webobjects.appserver._private.WOKeyValueAssociation.valueInComponent(WOKeyValueAssociation.java:50)
at com.webobjects.appserver._private.WOSubmitButton.invokeAction(WOSubmitButton.java:81)
at com.webobjects.appserver._private.WODynamicGroup.invokeChildrenAction(WODynamicGroup.java:105)
at com.webobjects.appserver._private.WODynamicGroup.invokeAction(WODynamicGroup.java:115)
at com.webobjects.appserver._private.WOForm.invokeAction(WOForm.java:141)
at com.webobjects.appserver._private.WODynamicGroup.invokeChildrenAction(WODynamicGroup.java:105)
at com.webobjects.appserver._private.WODynamicGroup.invokeAction(WODynamicGroup.java:115)
at com.webobjects.appserver._private.WOComponentContent.invokeAction(WOComponentContent.java:38)
at com.webobjects.appserver._private.WODynamicGroup.invokeChildrenAction(WODynamicGroup.java:105)
at com.webobjects.appserver._private.WODynamicGroup.invokeAction(WODynamicGroup.java:115)
at com.webobjects.appserver.WOComponent.invokeAction(WOComponent.java:1078)
at com.webobjects.appserver._private.WOComponentReference.invokeAction(WOComponentReference.java:127)
at com.webobjects.appserver._private.WODynamicGroup.invokeChildrenAction(WODynamicGroup.java:105)
at com.webobjects.appserver._private.WODynamicGroup.invokeAction(WODynamicGroup.java:115)
at com.webobjects.appserver.WOComponent.invokeAction(WOComponent.java:1078)
at com.webobjects.appserver.WOSession.invokeAction(WOSession.java:1357)
at com.webobjects.appserver.WOApplication.invokeAction(WOApplication.java:1736)
at com.webobjects.appserver._private.WOComponentRequestHandler._dispatchWithPreparedPage(WOComponentRequestHandler.java:206)
at com.webobjects.appserver._private.WOComponentRequestHandler._dispatchWithPreparedSession(WOComponentRequestHandler.java:298)
at com.webobjects.appserver._private.WOComponentRequestHandler._dispatchWithPreparedApplication(WOComponentRequestHandler.java:332)
at com.webobjects.appserver._private.WOComponentRequestHandler._handleRequest(WOComponentRequestHandler.java:369)
at com.webobjects.appserver._private.WOComponentRequestHandler.handleRequest(WOComponentRequestHandler.java:442)
at com.webobjects.appserver.WOApplication.dispatchRequest(WOApplication.java:1678)
at com.webobjects.appserver._private.WOWorkerThread.runOnce(WOWorkerThread.java:144)
at com.webobjects.appserver._private.WOWorkerThread.run(WOWorkerThread.java:226)
at java.lang.Thread.run(Thread.java:613)

I assume the "read only entity" is the newly-abstract Person.  But I don't have any Person entities---I've made Person.java an abstract class.  This is at a point where I'm trying to save a UserPreference whose 'person' relationship points to an AMPerson object.


-- 
Paul.

w  http://logicsquad.net/
h  http://paul.hoadley.name/


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  • Follow-Ups:
    • Re: Setting up horizontal inheritance
      • From: Chuck Hill <email@hidden>
References: 
 >Re: Setting up horizontal inheritance (From: Chuck Hill <email@hidden>)
 >Re: Setting up horizontal inheritance (From: Paul Hoadley <email@hidden>)
 >Re: Setting up horizontal inheritance (From: Ken Anderson <email@hidden>)

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