ConcurrentModificationException on the second commit updating a multi-valued object property

[cristianolongoodhl]

I'm using Jopa 2.1.0 with ontodriver-jena. My model consists of a Child class, and a Parent class with a property hasChild with a Set of Child as range. Once a Parent instance p is stored in the ontology, I need to add several instances of Child as children of p, one by one and using different transactions. Using an in-memory storage, two additions works well. Instead, using a file storage, only the first addition works fine, where as the second one cause the runtime exception reported below.

A test showing this use case both with in-memory and file storage is available at https://github.com/cristianolongoodhl/jopamiltivaluedpropertiesissue.

Also, workaround suggestions are welcome.

`cz.cvut.kbss.jopa.exceptions.RollbackException: java.util.ConcurrentModificationException

at cz.cvut.kbss.jopa.transactions.EntityTransactionWrapper.commit(EntityTransactionWrapper.java:56)
at cz.cvut.kbss.jopa.transactions.EntityTransactionImpl.commit(EntityTransactionImpl.java:58)
at it.unict.gallosiciliani.importing.persistence.LexiconOntologyWriterTest.testStoringMultipleEntriesAtomic(LexiconOntologyWriterTest.java:169)
at java.base/java.lang.reflect.Method.invoke(Method.java:569)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)

Caused by: java.util.ConcurrentModificationException
at org.apache.jena.mem.ArrayBunch$2.forEachRemaining(ArrayBunch.java:130)
at org.apache.jena.util.iterator.WrappedIterator.forEachRemaining(WrappedIterator.java:113)
at org.apache.jena.util.iterator.FilterIterator.forEachRemaining(FilterIterator.java:97)
at org.apache.jena.util.iterator.WrappedIterator.forEachRemaining(WrappedIterator.java:113)
at org.apache.jena.mem.TrackingTripleIterator.forEachRemaining(TrackingTripleIterator.java:58)
at org.apache.jena.util.iterator.Map1Iterator.forEachRemaining(Map1Iterator.java:54)
at org.apache.jena.util.iterator.WrappedIterator.forEachRemaining(WrappedIterator.java:113)
at cz.cvut.kbss.ontodriver.jena.connector.LocalStorage.remove(LocalStorage.java:123)
at cz.cvut.kbss.ontodriver.jena.connector.SharedStorageConnector.lambda$removePropertyValues$6(SharedStorageConnector.java:160)
at java.base/java.lang.Iterable.forEach(Iterable.java:75)
at cz.cvut.kbss.ontodriver.jena.connector.SharedStorageConnector.removePropertyValues(SharedStorageConnector.java:158)
at cz.cvut.kbss.ontodriver.jena.connector.ChangeTrackingStorageConnector.mergeRemovedStatements(ChangeTrackingStorageConnector.java:80)
at cz.cvut.kbss.ontodriver.jena.connector.ChangeTrackingStorageConnector.commit(ChangeTrackingStorageConnector.java:59)
at cz.cvut.kbss.ontodriver.jena.JenaAdapter.commit(JenaAdapter.java:66)
at cz.cvut.kbss.ontodriver.jena.JenaConnection.commit(JenaConnection.java:66)
at cz.cvut.kbss.jopa.sessions.ConnectionWrapper.commit(ConnectionWrapper.java:103)
at cz.cvut.kbss.jopa.sessions.ChangeTrackingUnitOfWork.commitToStorage(ChangeTrackingUnitOfWork.java:114)
at cz.cvut.kbss.jopa.sessions.AbstractUnitOfWork.commitUnitOfWork(AbstractUnitOfWork.java:199)
at cz.cvut.kbss.jopa.sessions.AbstractUnitOfWork.commit(AbstractUnitOfWork.java:190)
at cz.cvut.kbss.jopa.transactions.EntityTransactionWrapper.commit(EntityTransactionWrapper.java:53)
`

[cristianolongoodhl]

The workaround is: add children by SPARQL queries.

[ledsoft]

Hi, thanks for reporting the issue as well as finding a workaround. I will try to look into it as soon as possible.