How to access entity manager with spring boot and spring data

Question

How can I get access to the Entity Manager in the repository when using Spring Boot and Spring Data?

Otherwise, I will need to put my big query in an annotation. I would prefer to have something more clear than a long text.

score 35 · Accepted Answer · edited Dec 27 '20 at 13:33

35

You would define a CustomRepository to handle such scenarios. Consider you have CustomerRepository which extends the default spring data JPA interface JPARepository<Customer,Long>

Create a new interface CustomCustomerRepository with a custom method signature.

public interface CustomCustomerRepository {
    public void customMethod();
}

Extend CustomerRepository interface using CustomCustomerRepository

public interface CustomerRepository extends JpaRepository<Customer, Long>, CustomCustomerRepository{

}

Create an implementation class named CustomerRepositoryImpl which implements CustomerRepository. Here you can inject the EntityManager using the @PersistentContext. Naming conventions matter here.

public class CustomCustomerRepositoryImpl implements CustomCustomerRepository {

    @PersistenceContext
    private EntityManager em;

    @Override
    public void customMethod() {
    
    }
}

edited Dec 27 '20 at 13:33

Community

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answered Jun 17 '15 at 08:45

Nitin Arora

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2

CustomerRepositoryImpl class should implement CustomCustomerRepository not CustomerRepository as only method of CustomCustomerRepository needs implementation – Nikhil Mahajan Dec 05 '16 at 09:45
Does this CustomCustomerRepositoryImpl work without a customMethod()? – Doc Brown Dec 11 '17 at 12:48
4

I am getting this error `No property customMethod found for type Customer` do I need to do any configuration ? – Rookie007 Jun 21 '19 at 03:55
1

If you get error "No property customMethod found for type Customer" remove annotation @PersistenceContext and inject the entityManager object via the constructor of CustomRepositoryImpl – cnmuc Jun 10 '20 at 10:18
@cnmuc can you elaborate on the solution you mentioned. I am facing the same issue as you mentioned. – Avik Aggarwal Oct 15 '20 at 19:12
2

@AvikAggarwal public class CustomerRepositoryImpl implements CustomCustomerRepository { private final EntityManager entityManager; public CustomerRepositoryImpl(EntityManager entityManager) { this.entityManager = entityManager; } } – cnmuc Oct 15 '20 at 19:53
Thanks @cnmuc. I had implemented that but now I face `No query defined for that name`. Any idea about this? Please note I am using a query to transform my table data to another shape defined as DTO. – Avik Aggarwal Oct 16 '20 at 06:08
Spring Data JPA Reference - https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#repositories.custom-implementations – Munish Chandel Dec 27 '20 at 13:03
Convoluted answer and doesn't work. What do we even inject to our main class? the Impl or Repository class? both ways I'm still getting the same error - Also - I have a JPA method on the `extends JpaRepository<>` interface that I need to use – ennth May 09 '21 at 00:31

Sergey Ushakov · Answer 2 · 2020-08-17T13:09:52.003

In case you have many repositories to deal with, and your need in EntityManager is not specific for any particular repository, it is possible to implement various EntityManager functionality in a single helper class, maybe something like that:

@Service
public class RepositoryHelper {

    @PersistenceContext
    private EntityManager em;

    @Transactional
    public <E, R> R refreshAndUse(
            E entity,
            Function<E, R> usageFunction) {
        em.refresh(entity);
        return usageFunction.apply(entity);
    }

}

The refreshAndUse method here is a sample method to consume a detached entity instance, perform a refresh for it and return a result of a custom function to be applied to the refreshed entity in a declarative transaction context. And you can add other methods too, including query ones...

NOTE Demo code was simplified upon the first silent downvote received. Further downvoters, if any, are still encouraged to spend a minute for dropping at least a line of comment, as is there any sense in silent downvoting? :)

How to access entity manager with spring boot and spring data

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