When calling StatelessSession.get(Class, Serializable, LockMode) with a null LockMode argument, a NullPointerException is thrown from the following code path:

java.lang.NullPointerException
	at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:4004)
	at org.hibernate.persister.entity.AbstractEntityPersister.load(AbstractEntityPersister.java:3989)
	at org.hibernate.internal.StatelessSessionImpl.get(StatelessSessionImpl.java:182)
	at org.hibernate.internal.StatelessSessionImpl.get(StatelessSessionImpl.java:170)

When the counterpart Session.get(Class<T>, Serializable, LockMode) is called with a null LockMode, it doesn't throw an exception (and works just fine).

It seems like the LockOptions instance in AbstractEntityPersister.getAppropriateLoader(LockOptions, SharedSessionContractImplementor) has different values for its {{lockMode field LockMode.NONE in case of a stateful Session, and null in case of a StatelessSession. So getLoaders().get(null) returns a null UniqueEntityLoader, and attempting to call UniqueEntityLoader.load(Serializable, Object, SharedSessionContractImplementor, LockOptions) will throw the NullPointerException.

In case of a stateful Session, the LoadEvent(Serializable, String, Object, LockOptions, boolean, EventSource) constructor has the following code:

if ( lockOptions.getLockMode() == null ) {
  lockOptions.setLockMode(DEFAULT_LOCK_MODE);
}

There is no similar default value check for the StatelessSession code path.

Maybe the StatelessSession should set the default LockMode.NONE lock mode when a null argument is passed? It would be more in line with the stateful Session, and would not throw NullPointerException.