ClassCastException when changing a collection association to a set if @PreUpdate listener exists in Hibernate

Environment

• Red Hat JBoss Enterprise Application Platform (EAP) 7
• Hibernate 5

Issue

• An association is defined between two entities and a PreUpdate listener is used

      public class EmployeeListener {
          @PreUpdate
          void onPreUpdate(Object o) {
          }
      }
  
      @Entity
      @EntityListeners( EmployeeListener.class )
      public class Employee {
          ...
          @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY)
          protected Collection<Task> tasks;
          ...
      }
  
      @Entity
      public class Task {
          ...
      }
  

• Though the association is defined to use collection/bag semantics, it is being assigned a set

  HashSet<Task> tasks = new HashSet<Task>();
  tasks.add(new Task("Some work"));
  employee.setTasks(tasks);
  entityManager.merge(employee);
  entityManager.flush();
  

• A ClassCastException is raised during flush after the update of the association

  java.lang.ClassCastException: java.util.HashSet cannot be cast to org.hibernate.collection.spi.PersistentCollection
  	at org.hibernate.event.internal.FlushVisitor.processCollection(FlushVisitor.java:43)
  	at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:104)
  	at org.hibernate.event.internal.AbstractVisitor.processValue(AbstractVisitor.java:65)
  	at org.hibernate.event.internal.AbstractVisitor.processEntityPropertyValues(AbstractVisitor.java:59)
  	at org.hibernate.event.internal.DefaultFlushEntityEventListener.onFlushEntity(DefaultFlushEntityEventListener.java:166)
  	at org.hibernate.event.internal.AbstractFlushingEventListener.flushEntities(AbstractFlushingEventListener.java:235)
  	at org.hibernate.event.internal.AbstractFlushingEventListener.flushEverythingToExecutions(AbstractFlushingEventListener.java:94)
  	at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:38)
  	at org.hibernate.internal.SessionImpl.doFlush(SessionImpl.java:1483)
  	at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1469)
  

Resolution

This issue¹ is resolved in This content is not included.EAP 7.2 cumulative patch (CP) 4 and later releases. Production systems should use the latest available cumulative patch.

Root Cause

This is a known defect (Content from hibernate.atlassian.net is not included.HHH-13466).

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