Lazy loading problem when property-ref is used for collections -------------------------------------------------------------- Key: HHH-1820 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-1820 Project: Hibernate3 Issue Type: Bug Affects Versions: 3.1.3 Environment: Oracle 8.1.7 Reporter: Jakub Mendys Consider mapping <class name="MedDRATerm" table="MBROW_MEDDRA_TERMS" mutable="false" batch-size="50"> <cache usage="read-only" region="dictionary" /> <id name="medDRATermId" type="long" column="TERM_ID"> <generator class="assigned" /> </id> <map name="termNames" table="MBROW_TERM_NAMES" lazy="true" batch-size="50"> <cache usage="read-only" region="dictionary" /> <key column="MEDDRA_CODE" property-ref="medDRACode" /> <index column="LANGUAGE_ID" type="com.roche.dss.meddra.dao.type.LanguageType" /> <element column="NAME" type="string" /> </map> <property name="medDRACode" column="MEDDRA_CODE" type="com.roche.dss.meddra.dao.type.MedDRACodeType" /> </class> <class name="MedDRATermInstance" table="MBROW_MEDDRA_TREES" mutable="false"> <cache usage="read-only" region="dictionary" /> <id name="medDRATermInstanceId" type="long" column="NODE_ID"> <generator class="assigned" /> </id> <many-to-one name="medDRATerm" class="MedDRATerm" column="TERM_ID" fetch="join" not-null="true" insert="false" update="false" /> </class> When you execute a query: from MedDRATermInstance i where i.version=:versionId and i.medDRATerm in (:terms) and then using the _same session_ you will iterate over returned collection and will call session.get(id) for returned records it is very likely that for _SOME_ (random??) of objects when you will try to access its properties you will get following exception thrown: 2006-06-07 19:25:11,942 ERROR org.hibernate.LazyInitializationException - failed to lazily initialize a collection of role: com.roche.dss.meddra.model.MedDRATerm.termNames, no session or session was losed org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.roche.dss.meddra.model.MedDRATerm.termNames, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:358) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:350) at org.hibernate.collection.AbstractPersistentCollection.readElementByIndex(AbstractPersistentCollection.java:151) at org.hibernate.collection.PersistentMap.get(PersistentMap.java:127) Calling session.clear() before session.get() helps to workaround this but causes all the records to be fethed again from the database.