Spring managed transactions, EclipseLink JPA, custom isolation level

Question

I suspect this one is embarrassing an I am doing it wrong in a terrible way, but please bear with me.

I have a Spring application with Spring-managed transactions. It uses EclipseLink JPA. I have a method which does a findByNativeQuery() followed by a merge(). I need this to happen in a real SERIAL transaction isolation level. I tried adding @Transactional(isolation=Isolation.SERIALIZABLE)

This doesn't work because org.springframework.orm.jpa.vendor.EclipseLinkJpaDialect#beginTransaction does not support any transaction isolation level but the default. So then I tried getting to UnitOfWork internals of ElcipseLink and starting/comitting my own transactions, but then I get an error:

"java.lang.IllegalStateException : Not allowed to create transaction on shared EntityManager - use Spring transactions or EJB CMT instead

Which of course makes sense... but what do I do??

Answer 1

I've given a try to this, but I am not completely sure of the solution. I've taken the code from this blog and adapted it for EclipseLink. Here's the code:

package com.byteslounge.spring.tx.dialect;

import java.sql.SQLException;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceException;

import org.eclipse.persistence.sessions.UnitOfWork;
import org.springframework.orm.jpa.vendor.EclipseLinkJpaDialect;
import org.springframework.transaction.TransactionDefinition;
import org.springframework.transaction.TransactionException;

public class CustomEclipseLinkJpaDialect extends EclipseLinkJpaDialect {

    private static final long serialVersionUID = 1L;

    private boolean lazyDatabaseTransaction = false;

    @Override
    public void setLazyDatabaseTransaction(boolean lazyDatabaseTransaction) {
        this.lazyDatabaseTransaction = lazyDatabaseTransaction;
    }

    @Override
    public Object beginTransaction(final EntityManager entityManager,
            final TransactionDefinition definition)
            throws PersistenceException, SQLException, TransactionException {

        UnitOfWork uow = (UnitOfWork) getSession(entityManager);
        uow.getLogin().setTransactionIsolation(definition.getIsolationLevel());

        entityManager.getTransaction().begin();
        if (!definition.isReadOnly() && !lazyDatabaseTransaction) {
            uow.beginEarlyTransaction();
        }

        return null;
    }
}

I'm seeing the SERIALIZABLE isolation being logged when the transaction is initiated, but this needs to be tested properly to confirm it works.

Answer 2

Support for custom isolation level was added in Spring 4.1.2 to EclipseLinkJpaDialect