ConcurrentModificationException with <many-to-one property_ref="..."/> in a set of composite elements ----------------------------------------------------------------------------------------------------- Key: HHH-971 URL: http://opensource.atlassian.com/projects/hibernate/browse/HHH-971 Project: Hibernate Core Issue Type: Bug Components: core Environment: Hibernate 3.1 beta 3, Java 1.4.2_08 Reporter: Emmanuel Bourg Assignee: Diego Plentz I tried to drop the latest 3.1-beta3 jar in my application currently working with hibernate 3.0.5 to test the new features and found out that an exception is now thrown when the SessionFactory is build : java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:448) at java.util.AbstractList$Itr.remove(AbstractList.java:433) at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1006) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1120) at myapp.dao.impl.hibernate.SessionManager.init(SessionManager.java:74) I tracked down the issue to the mapping of a many-to-one association using a property-ref inside a set of composite elements. The mapping generating this error looks like this: <set name="children" table="CHILD"> <key column="PARENT_ID"/> <composite-element class="Child"> <many-to-one name="foo" column="FOO" property-ref="alternateId"/> </composite-element> </set> A many-to-one association with a property-ref outside a composite element didn't cause this exception.