JPA Interface extending JpaRepository only, with use of EntityManager in default methods

user_18306365 0
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First of all, for those who wanted to know how to use an EntityManager in an interface extending a JpaRepository. Here is a potential solution. But !!! I'm aware this is maybe a baaaad practice, and experienced people in Spring and JPA will maybe try to kill me ;) apologizes...

So, after this BIG warning, here is my question :

I would like to use only interfaces without a Custom implementation and this is what I did :

@Repository
@Transactional
public interface BookingDao extends JpaRepository<Booking, Long> {

    Booking findByCodeId(String codeId);

    void deleteByCodeId(String codeId);

    default Integer findCountOfBookingOldDay() {
        EntityManager entityManager = ApplicationContextProvider.getEntityManager();
        Query query = entityManager.createNativeQuery("XXXX");
        Number result = (Number) query.getSingleResult();
        return result.intValue();
    }
}

    @Component(value = "applicationContextProvider")
    public class ApplicationContextProvider implements ApplicationContextAware {
        private static ApplicationContext context;
        public static ApplicationContext getApplicationContext() {
            return context;
        }
        public static EntityManager getEntityManager() {
            return EntityManagerFactoryUtils.getTransactionalEntityManager(context.getBean(LocalContainerEntityManagerFactoryBean.class).getObject());
            return context.getBean(EntityManager.class);
        }
        @Override
        public void setApplicationContext(ApplicationContext ac) throws BeansException {
            context = ac;
        }
}

I'm aware this is maybe not the best practice, and the best way would be to use @PersistenceContext (takes care to create a unique EntityManager for every thread) in a class... But what would be in my case the best alternative :

this :

return EntityManagerFactoryUtils.getTransactionalEntityManager(context.getBean(LocalContainerEntityManagerFactoryBean.class).getObject());

or this :

return context.getBean(EntityManager.class)

or maybe another better way, still by using only interface.

Thank you for your remarks/advices.

PS: "EntityManagerFactoryUtils" is not doing the same as PersistenceContext ?

spring-data-jpa spring java
1 Answers

For what you want to do I'd annotate a method in the interface by @Query("<your native select counting what you need>", native=true).

When I need any fancy logic, I usually create a service, which is using the repository like this:

@Service
@Transactional
public class MyService {

    private final MyRepository repository;

    @Autowired
    public MyService (MyRepository repository) {
        this.repository = repository;
    }

    public int myMethod(){
        //code using repository
    }

}
user_27179580
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