Integration of JOPA transactions into the Spring declarative transactions - the @Transactional annotation.

• Isolation level configuration is currently not supported because it is not supported by JOPA either.
• When a method is not transactional, the library with create an EntityManager instance, which will be automatically closed after one operation/query execution.
• Nested transactions are validated, so a read-write transaction cannot be nested in a read-only transaction.

Usage of the library is fairly simple. It is only necessary to instantiate the JopaTransactionManager and DelegatingEntityManager Spring beans.

• JopaTransactionManager implements Spring's TransactionManager interface and Spring calls it at significant moments of the transaction lifecycle (begin, commit, etc.),
• DelegatingEntityManager implements JOPA's EntityManager interface and is injected into transactional Spring beans, where it delegates calls to the EntityManager instance bound to the current transaction. This is the only class with which the end users directly interact.

Do not forget to EnableTransactionManagement.

Assuming there is an EntityManagerFactory Spring bean, Java-based configuration of the aforementioned beans looks for example as follows:

@Configuration
@EnableTransactionManagement
@Import(PersistenceFactory.class)
public class PersistenceConfig {

    @Bean
    public DelegatingEntityManager entityManager() {
        return new DelegatingEntityManager();
    }

    @Bean(name = "txManager")
    public PlatformTransactionManager transactionManager(EntityManagerFactory emf, 
                                                         DelegatingEntityManager emProxy) {
        return new JopaTransactionManager(emf, emProxy);
    }
}

EntityManager is then injected into beans using Autowired or Inject (PersistenceContext is currently not supported, as it is closely tied to JPA):

@Autowired
private EntityManager em;

The tests contain a complete setup. For a fully operational example, see JOPA Example 04 - JOPA + Spring and the JSON-LD demo.

A full-fledged information system using JOPA and declarative Spring transactions is TermIt.

The library is now available in Maven central, so getting it is just a matter of adding a Maven dependency:

<dependency>
    <groupId>com.github.ledsoft</groupId>
    <artifactId>jopa-spring-transaction</artifactId>
</dependency>

See https://github.com/kbss-cvut/jopa.

MIT