Concurrent access issue with JPA for a Select query?

Question

Hi All,
I have been trying to understand why this code,
public <T> List<T> findManyNativeSql(String queryString, Class<T> resultClass)
            Query aQuery = getEntityManager().createNativeQuery(queryString,resultClass); // Throwing the following exceptionis causing this exception.
<openjpa-1.1.0-r422266:657916 fatal general error> org.apache.openjpa.persistence.PersistenceException: Multiple concurrent th
reads attempted to access a single broker. By default brokers are not thread safe; if you require and/or intend a broker to be
accessed by more than one thread, set the openjpa.Multithreaded property to true to override the default behavior.
        at org.apache.openjpa.kernel.BrokerImpl.endOperation(BrokerImpl.java:1789)
        at org.apache.openjpa.kernel.BrokerImpl.isActive(BrokerImpl.java:1737)
        at org.apache.openjpa.kernel.DelegatingBroker.isActive(DelegatingBroker.java:428)
        at org.apache.openjpa.persistence.EntityManagerImpl.isActive(EntityManagerImpl.java:606)
        at org.apache.openjpa.persistence.PersistenceExceptions$2.translate(PersistenceExceptions.java:66)
        at org.apache.openjpa.kernel.DelegatingBroker.translate(DelegatingBroker.java:102)
        at org.apache.openjpa.kernel.DelegatingBroker.newQuery(DelegatingBroker.java:1227)I have tried looking at the query which gets printed in the logs when the exception is thrown
[[ACTIVE] ExecuteThread: '32' for queue: 'weblogic.kernel.Default (self-tuning)'] ERROR jpa
- ID: 133  queryString= select * from Details where cust_name='SETH'Any suggestions on the following would be very helpful
Also, AppServer: WL10.3 is being used.
VR

Answer 1

I'm not sure what a Broker is in OpenJPA so you may want to post in an OpenJPA forum. I would suspect though that a broker is underneath the EntityManager, and it might suggest that this EntityManager instance is being shared among threads. Verify that the EntityManager returned is not being used in multiple threads; if it is used in multiple threads concurrently, this needs to be changed to obtian a new one and release it when done as they are not thread safe. You might also try using EclipseLink as the JPA provider to see if you get a different error message that might point out the problem.
Best Regards,
Chris