The problem was introduced with the HHH-11097, see some backround at: ClassCastException: Object; cannot be cast to Collection.

Have a local tetscase written for the problem in org.hibernate.test.querycache.QueryCacheTest and will push that.

The root caus is the method that creates the "loggableString" that was changed in the above HHH-11097 Closed . However there are a few precondition that is needed to see the problem:

• USE_SECOND_LEVEL_CACHE = true
• USE_STRUCTURED_CACHE = true

Then the class that is to be persisted into the L2Cache must have an embededId and at least some attribute that is a "OneToMany", "MenuToMany", etc. The fault occurs when we get a hit in the L2Cache when we try to read it:

{{Caused by: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to java.util.Collection
at org.hibernate.type.CollectionType.getElementsIterator(CollectionType.java:250)
at org.hibernate.type.CollectionType.renderLoggableString(CollectionType.java:208)
at org.hibernate.type.CollectionType.toLoggableString(CollectionType.java:198)
at org.hibernate.type.TypeHelper.toLoggableString(TypeHelper.java:439)
at org.hibernate.cache.spi.entry.StructuredCacheEntry.destructure(StructuredCacheEntry.java:54)
at org.hibernate.event.internal.DefaultLoadEventListener.processCachedEntry(DefaultLoadEventListener.java:612)
at org.hibernate.event.internal.DefaultLoadEventListener.loadFromSecondLevelCache(DefaultLoadEventListener.java:602)
at org.hibernate.event.internal.DefaultLoadEventListener.doLoad(DefaultLoadEventListener.java:462)
at org.hibernate.event.internal.DefaultLoadEventListener.load(DefaultLoadEventListener.java:219)
at org.hibernate.event.internal.DefaultLoadEventListener.proxyOrLoad(DefaultLoadEventListener.java:278)
at org.hibernate.event.internal.DefaultLoadEventListener.doOnLoad(DefaultLoadEventListener.java:121)
at org.hibernate.event.internal.DefaultLoadEventListener.onLoad(DefaultLoadEventListener.java:89)
at org.hibernate.internal.SessionImpl.fireLoad(SessionImpl.java:1239)
at org.hibernate.internal.SessionImpl.internalLoad(SessionImpl.java:1122)
at org.hibernate.type.EntityType.resolveIdentifier(EntityType.java:646)
at org.hibernate.type.EntityType.resolve(EntityType.java:431)
at org.hibernate.engine.internal.TwoPhaseLoad.doInitializeEntity(TwoPhaseLoad.java:165)
at org.hibernate.engine.internal.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:125)
at org.hibernate.loader.Loader.initializeEntitiesAndCollections(Loader.java:1152)
at org.hibernate.loader.Loader.processResultSet(Loader.java:1011)
at org.hibernate.loader.Loader.doQuery(Loader.java:949)
at org.hibernate.loader.Loader.doQueryAndInitializeNonLazyCollections(Loader.java:341)
at org.hibernate.loader.Loader.doList(Loader.java:2692)
at org.hibernate.loader.Loader.doList(Loader.java:2675)
at org.hibernate.loader.Loader.listIgnoreQueryCache(Loader.java:2507)
at org.hibernate.loader.Loader.list(Loader.java:2502)
at org.hibernate.loader.hql.QueryLoader.list(QueryLoader.java:502)
at org.hibernate.hql.internal.ast.QueryTranslatorImpl.list(QueryTranslatorImpl.java:384)
at org.hibernate.engine.query.spi.HQLQueryPlan.performList(HQLQueryPlan.java:216)
at org.hibernate.internal.SessionImpl.list(SessionImpl.java:1490)
at org.hibernate.query.internal.AbstractProducedQuery.doList(AbstractProducedQuery.java:1445)
at org.hibernate.query.internal.AbstractProducedQuery.list(AbstractProducedQuery.java:1414)
at org.hibernate.query.Query.getResultList(Query.java:146)
at org.hibernate.query.criteria.internal.compile.CriteriaQueryTypeQueryAdapter.getResultList(CriteriaQueryTypeQueryAdapter.java:72)}}