AbstractEntityPersister.getNaturalIdentifierSnapshot doesn't work with many-to-one ids -------------------------------------------------------------------------------------- Key: HHH-1574 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1574 Project: Hibernate Core Issue Type: Patch Affects Versions: 3.1.2 Reporter: Alex Burgel Attachments: resolveentity.patch, resolveentity32.patch, testcase.zip i just upgraded from 3.0.5 to 3.1.2, and i started seeing this problem. i'm not exactly sure where the bug is here, but this is what i'm seeing: i have a class, Subscription, which has a natural-id of class Subscriber and Edition (excerpts of relevant mapping files below). when Subscription is unloaded, if i make a change, then commit the session, i see this exception: HibernateException: immutable natural identifier of an instance of Subscription was altered this gets thrown from DefaultFlushEntityEventListener.checkNaturalId() line 80. i traced through that method, this is what happens: 1. in checkNaturalId, loaded == null , so getNaturalIdSnapshot() is called 2. this ends up generating some sql that selects the SubscriptionId and EditionId from the Subscription row. 3. the sql is generated in AbstractEntityPersister.getNaturalIdentifierSnapshot(), which calls hydrate for each returned column of the natural-id, 4. but hydrate only returns the id, instead of the actual entity 5. so this array of ids (instead of entities) ends up back in DefaultFlushEntityEventListener.checkNaturalId() as 'loaded', which gets compared to 'current' the trouble is that 'current' contains the entities, but 'loaded' only contains the ids of those entites, so the natural-id check fails, and i get the exception. this only happens when 'loaded' is null in checkNaturalId(). the javadocs for hydrate say you have to call "resolve" afterwards... this isn't being done, so maybe thats the fix. if the natural-id is not just simple properties, then resolve should also be called. <class name="Subscription" table="Subscriptions" batch-size="10"> <id name="id" column="Id" type="int"><generator class="native" /></id> <natural-id> <many-to-one name="subscriber" class="Subscriber" column="SubscriberId" /> <many-to-one name="edition" class="Edition" column="EditionId" /> </natural-id> .... </class> <class name="Subscriber" table="Subscriber"> <id name="id" column="id" type="int"><generator class="native" /></id> <map name="subscriptions" inverse="true" cascade="all,delete-orphan" batch-size="10"> <key column="SubscriberId" /> <map-key-many-to-many column="EditionId" class="Edition" /> <one-to-many class="Subscription" /> </map> </class>