I was using the Hibernate Entity Manager. I built a network model of objects from the annotated classes as well as the non-annotated classes. When I was done with the internal data object creation, I tried to save objects to the MySQL database. The first time I called a method in the Persistent class, Hibernate threw the "ConcurrentModificationException:"

entityManagerFactory = Persistence.createEntityManagerFactory("manager");

The line above caused the exception. I don't understand why. Does that mean that Hibernate had already created the entity manager factory before I invoked the createEntityManagerFactory method? How can I resolve this exception?



Hibernate versions:

hibernate-3.2
hibernate-annotations-3.3.0.GA
hibernate-entitymanager-3.3.1.GA

I am using the Entity Manager which includes all the above core libraries.

Full stack trace of any exception that occurs:

Exception in thread "main" javax.persistence.PersistenceException: java.util.ConcurrentModificationException
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:258)
at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:120)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:51)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
at com.cra.trek2.model.database.DataEntityManager.<init>(DataEntityManager.java:29)
at com.cra.trek2.model.base.ConceptMapFactory.createConceptMap(ConceptMapFactory.java:43)
at com.cra.trek2.demo.DemoRunner.testCxlImport(DemoRunner.java:225)
at com.cra.trek2.demo.DemoRunner.main(DemoRunner.java:51)
Caused by: java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.remove(Unknown Source)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1131)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:316)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1115)
at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1269)
at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:150)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:888)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:186)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:246)
... 7 more


Name and version of the database you are using:

mysql-connector-java-3.1.13-bin.jar

probably yes. If you use JPA outside an container you are responsible to configure the manager only once. This is the same as with a Hibernate SessionFactory.

You might put the configuration inside a static block to guaranty this.

Following the advice from Sebastian, I tried to set up a static initialization in my main class, but Hibernate still threw the ConcurrentModificationException.

I am not sure if Hibernate could not handle complex convoluted relationships among the entities. For example, class A has a 1-to-Many relationship with class B through a HashMap attribute. Class B has an abstract super class S that has a 1-To-Many relationship to class C. Class C in turn has a Many-to-1 relationship with Class S twice because of the presence of two distinct attributes of the same type. I used JOINED as the inheritance strategy (i.e., table per subclass) for entity classes as well as some value type components.

Here is the new exception trace:

java.lang.ExceptionInInitializerError
Caused by: javax.persistence.PersistenceException: java.util.ConcurrentModificationException
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:258)
at org.hibernate.ejb.HibernatePersistence.createEntityManagerFactory(HibernatePersistence.java:120)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:51)
at javax.persistence.Persistence.createEntityManagerFactory(Persistence.java:33)
at com.cra.trek2.model.database.DataEntityManager.<init>(DataEntityManager.java:29)
at com.cra.trek2.demo.DemoRunner.<clinit>(DemoRunner.java:37)
Caused by: java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(Unknown Source)
at java.util.AbstractList$Itr.remove(Unknown Source)
at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1131)
at org.hibernate.cfg.AnnotationConfiguration.secondPassCompile(AnnotationConfiguration.java:316)
at org.hibernate.cfg.Configuration.buildMappings(Configuration.java:1115)
at org.hibernate.ejb.Ejb3Configuration.buildMappings(Ejb3Configuration.java:1269)
at org.hibernate.ejb.EventListenerConfigurator.configure(EventListenerConfigurator.java:150)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:888)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:186)
at org.hibernate.ejb.Ejb3Configuration.configure(Ejb3Configuration.java:246)
... 5 more
Exception in thread "main"

Hibernate seemed to have problem mapping a collection of values in one of my classes causing the ConcurrentModificationException. For the sake of discussion, let's have the following classes:



I still don't understand why Hibernate always threw the ConcurrentModificationException whenever I uncommented the field "m" in class A. Could someone in the Hibernate team provide some insights here?

Regards,
William

I am facing a similar problem - http://forum.hibernate.org/viewtopic.php?t=979164&highlight=.

I have not come across any documentation that suggests of any existing limitation for doing the above. So i am assuming this could be an issue in hibernate. Can anyone confirm ?