在JpaRepository中不使用@Query注释

Question

I have the User entity in the database and it's JPA entity. I also have the UserDescription class which hasn't table in the database. I want to instantiate UserDescription class using different tables and entities. But I don't want to use EntityManager for it. So I found SELECT new ... pattern which can be used in @Query annotation, it's the perfect solution.

But I have simple issue - I need to annotate some method declaration which should be in interface. Usually it's done in JpaRepository , but UserDescription - isn't entity, so I can't do this!

Also, I tried to create POJO interface( UserDescriptionService ) with method declaration which annotated using @Query annotation, tried to create field with this interface in the controller(), and annotated it with Autowired and of course got:

Field userDescriptionService in UserController required a bean of type 'UserDescriptionService' that could not be found.

So, how can I use @Query annotation not in the JpaRepository or how can I get JpaRepository for the non-entity class?

Answer 1

As M. Deinum already mentioned. You are not forced to return only Entities in JpaRepositories.

You can use the Constructor Expression (aka select new) or also projections. Find more about projections here:

https://docs.spring.io/spring-data/jpa/docs/2.0.9.RELEASE/reference/html/#projections