By default, database transactions are started early. This allows - * for reusing the same JDBC Connection throughout an entire transaction, - * including read operations, and also for exposing EclipseLink transactions - * to JDBC access code (working on the same DataSource). - *
It is only recommended to switch this flag to "true" when no JDBC access - * code is involved in any of the transactions, and when it is acceptable to - * perform read operations outside of the transactional JDBC Connection. + * Set whether to lazily start a database resource transaction within a + * Spring-managed EclipseLink transaction. + *
By default, read-only transactions are started lazily but regular + * non-read-only transactions are started early. This allows for reusing the + * same JDBC Connection throughout an entire EclipseLink transaction, for + * enforced isolation and consistent visibility with JDBC access code working + * on the same DataSource. + *
Switch this flag to "true" to enforce a lazy database transaction begin + * even for non-read-only transactions, allowing access to EclipseLink's + * shared cache and following EclipseLink's connection mode configuration, + * assuming that isolation and visibility at the JDBC level are less important. * @see org.eclipse.persistence.sessions.UnitOfWork#beginEarlyTransaction() */ public void setLazyDatabaseTransaction(boolean lazyDatabaseTransaction) { @@ -72,11 +74,10 @@ public class EclipseLinkJpaDialect extends DefaultJpaDialect { public Object beginTransaction(EntityManager entityManager, TransactionDefinition definition) throws PersistenceException, SQLException, TransactionException { - UnitOfWork uow = entityManager.unwrap(UnitOfWork.class); - if (definition.getIsolationLevel() != TransactionDefinition.ISOLATION_DEFAULT) { // Pass custom isolation level on to EclipseLink's DatabaseLogin configuration // (since Spring 4.1.2) + UnitOfWork uow = entityManager.unwrap(UnitOfWork.class); uow.getLogin().setTransactionIsolation(definition.getIsolationLevel()); } @@ -85,7 +86,7 @@ public class EclipseLinkJpaDialect extends DefaultJpaDialect { if (!definition.isReadOnly() && !this.lazyDatabaseTransaction) { // Begin an early transaction to force EclipseLink to get a JDBC Connection // so that Spring can manage transactions with JDBC as well as EclipseLink. - uow.beginEarlyTransaction(); + entityManager.unwrap(UnitOfWork.class).beginEarlyTransaction(); } return null;