Closing for 4.1 release

Fixed by HHH-5472.

Btw. it seems very probable that the sequence the following operations done in saveTransientEntity (see source on github)

• read global checkNullability flag

• change global checkNullability flag to true

• restore global checkNullability flag to read value

when executed by 2 threads at the same time can change checkNullability flag to true for ever. For this to happen it's enough that

• first thread reads the flag and sets it temporarily to true

• second thread reads true (the temporary value)

• first thread completes merge and restores flag to the original value

• second threads completes merge and restores flag to the temporary value of true

Steps to reproduce should be as follow:

1. take an entity class E with non-null field

2. set checkNullability to false

3. If you now execute merge on new instance of E, you shall not receive PropertyValueException. If you have additional validation defined for entity E, you could receive javax.validation.ConstraintViolationException instead

4. Repeat step no. 3 in two threads several times. In DefaultMergeEventListener.mergeTransientEntity PropertyValueException is caught and handled this way:

   if ( isNullabilityCheckedGlobal( source ) ) { throw ex; } else { // retry save w/o checking for non-nullable properties // (the failure will be detected later) saveTransientEntity( copy, entityName, requestedId, source, copyCache, false ); }

   Because isNullabilityCheckedGlobal is affected by by the other thread, it can, incorrectly return true.

Have not managed to create a simple test case where this bug can be replicated, but with ongoing load testing, it is happening frequently. We have managed to remove all of the scenarios from our application code where null checking causes us a problem - except for one exception which occurs at approx line 104 in DefaultMergeEventListener.java

if ( isNullabilityCheckedGlobal( event.getSession() ) ) {
throw new TransientObjectException(
"one or more objects is an unsaved transient instance - save transient instance(s) before merging: " +
transientEntityNames );
}