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Using Spring-Managed Event Listeners in Hibernate

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Using Spring-Managed Event Listeners in Hibernate

Learn from Bozhidar Bozhanov of TomTom about a new and better way to use listeners in Hibernate (because the old way is broken).

· Java Zone
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Hibernate offers event listeners as part of its SPI. You can hook your listeners to a number of events, including pre-insert, post-insert, pre-delete, flush, etc.

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But sometimes in these listeners, you want to use spring dependencies. I’ve written previously on how to do that, but Hibernate has been upgraded and now there’s a better way (and the old way isn’t working in the latest versions because of missing classes).

This time it’s simpler. You just need a bean that looks like this:

@Component
public class HibernateListenerConfigurer {

    @PersistenceUnit
    private EntityManagerFactory emf;

    @Inject
    private YourEventListener listener;

    @PostConstruct
    protected void init() {
        SessionFactoryImpl sessionFactory = emf.unwrap(SessionFactoryImpl.class);
        EventListenerRegistry registry = sessionFactory.getServiceRegistry().getService(EventListenerRegistry.class);
        registry.getEventListenerGroup(EventType.POST_INSERT).appendListener(listener);
        registry.getEventListenerGroup(EventType.POST_UPDATE).appendListener(listener);
        registry.getEventListenerGroup(EventType.POST_DELETE).appendListener(listener);
    }
}

It is similar to this Stack Overflow answer, which however won’t work because it also relies on deprecated calsses.

You can also inject a List<..> of listeners (though they don’t share a common interface, you can define your own).

As pointed out in the SO answer, you can’t store new entities in the listener, so it’s no use injecting a DAO, for example. But it may come in handy to process information that does not rely on the current session.

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Topics:
hibernate ,listener ,spring

Published at DZone with permission of Bozhidar Bozhanov, DZone MVB. See the original article here.

Opinions expressed by DZone contributors are their own.

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