Comment 1 David Minsky 2011-06-07 17:40:06 EDT

This error may occur when two parent objects are (incorrectly) referencing the same aggregate object. Resolving this issue will contribute to how diagnosable this potential problem is in the long run.

Comment 2 David Minsky 2011-06-07 17:45:38 EDT

Created attachment 197547 [details]
Proposed fix

Proposed fix.
Follows same pattern as the implementation of the same superclass method in InstanceVariableAttributeAccessor.

Comment 3 David Minsky 2011-06-09 10:41:21 EDT

"reproduced" the incorrect scenario of sharing aggregate objects in EL trunk:

Local Exception Stack: 
Exception [EclipseLink-69] (Eclipse Persistence Services - @VERSION@.@QUALIFIER@): org.eclipse.persistence.exceptions.DescriptorException
Exception Description: A NullPointerException was thrown while extracting a value from the instance variable [endDate] in the object [null].
Internal Exception: java.lang.NullPointerException
Mapping: org.eclipse.persistence.mappings.DirectToFieldMapping[endDate-->EMPLOYEE.END_DATE]
Descriptor: RelationalDescriptor(examples.sessions.threetier.model.EmploymentPeriod --> [DatabaseTable(EMPLOYEE), DatabaseTable(SALARY)])
	at org.eclipse.persistence.exceptions.DescriptorException.nullPointerWhileGettingValueThruInstanceVariableAccessor(DescriptorException.java:1263)
	at org.eclipse.persistence.internal.descriptors.InstanceVariableAttributeAccessor.getAttributeValueFromObject(InstanceVariableAttributeAccessor.java:88)
	at org.eclipse.persistence.mappings.DatabaseMapping.getAttributeValueFromObject(DatabaseMapping.java:516)
	at org.eclipse.persistence.mappings.foundation.AbstractDirectMapping.compareObjects(AbstractDirectMapping.java:455)
	at org.eclipse.persistence.mappings.foundation.AbstractDirectMapping.compareForChange(AbstractDirectMapping.java:407)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.createObjectChangeSetThroughComparison(DeferredChangeDetectionPolicy.java:165)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.createObjectChangeSet(DeferredChangeDetectionPolicy.java:137)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.calculateChanges(DeferredChangeDetectionPolicy.java:89)
	at org.eclipse.persistence.internal.descriptors.ObjectBuilder.compareForChange(ObjectBuilder.java:1964)
	at org.eclipse.persistence.mappings.AggregateMapping.compareForChange(AggregateMapping.java:313)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.createObjectChangeSetThroughComparison(DeferredChangeDetectionPolicy.java:165)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.createObjectChangeSet(DeferredChangeDetectionPolicy.java:137)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.calculateChanges(DeferredChangeDetectionPolicy.java:89)
	at org.eclipse.persistence.descriptors.changetracking.DeferredChangeDetectionPolicy.calculateChangesForExistingObject(DeferredChangeDetectionPolicy.java:54)
	at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.calculateChanges(UnitOfWorkImpl.java:636)
	at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitToDatabaseWithChangeSet(UnitOfWorkImpl.java:1482)
	at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commitRootUnitOfWork(UnitOfWorkImpl.java:1317)
	at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.commit(UnitOfWorkImpl.java:1079)

Comment 4 David Minsky 2011-06-09 10:42:54 EDT

The following Employee demo-based example was used:

UnitOfWork uow = getSession().acquireUnitOfWork();
        
Employee employee1Original = new Employee();
Employee employee2Original = new Employee();

Employee employee1Clone = (Employee) uow.registerObject(employee1Original);
Employee employee2Clone = (Employee) uow.registerObject(employee2Original);
        
employee1Clone.setMale();
employee1Clone.setFirstName("Joe");
employee1Clone.setLastName("Someone");
employee1Clone.setSalary(1234);
employee1Clone.setPeriod(new EmploymentPeriod()); // not null

employee2Clone.setFemale();
employee2Clone.setFirstName("Jill");
employee2Clone.setLastName("Someone");
employee2Clone.setSalary(1234);
employee2Clone.setPeriod(null); // deliberately null

uow.commit();
        
uow = getSession().acquireUnitOfWork();

employee1Clone = (Employee)uow.registerObject(employee1Original);
// UoW backup clone's 'period' attribute is null
employee2Clone = (Employee)uow.registerObject(employee2Original);
        
employee2Clone.setPeriod(employee1Clone.getPeriod()); // 1. share the aggregate

uow.commit();

Comment 5 David Minsky 2011-06-24 13:56:35 EDT

Created attachment 198561 [details]
Proposed fix

Comment 6 David Minsky 2011-06-24 14:06:07 EDT

Aggregate sharing testcase no longer reproduces with the changes from:

Revision: 9610
Author: gyorke
Date: 2:47:23 PM, June 22, 2011
Message: Bug 300108 - Any changes that reference detached object will cause detached to be inserted

I've attached the exception fix I was working on, for brevity. This exception would be thrown, instead of an NPE when the attribute accessor attempted to invoke on a null object.

Comment 7 Eclipse Webmaster 2022-06-09 10:04:24 EDT

The Eclipselink project has moved to Github: https://github.com/eclipse-ee4j/eclipselink