Spring data CrudRepository exists

Question

When I extend CrudRepository interface, I have exists(ID) method in my subinteface. I can write findBy<property> methods.

Is it possible somehow to write existBy<property> method that will return boolean. Or to annotate it with @Query(jpa query) so it will return boolean.

I know that I can do select count(*) and return long, but then I will have to do !=0 check in my service layer.

Answer 1

@Oleksandr's answer is correct, but the only way I could get it to work is as follows. I'm using Eclipselink on PostgreSQL.

public interface UserRepository extends JpaRepository<User, Long> {     @Query("SELECT CASE WHEN COUNT(u) > 0 THEN 'true' ELSE 'false' END FROM User u WHERE u.username = ?1")     public Boolean existsByUsername(String username); } 

Answer 2

Actually you can use case expression like this:

select case when count(e) > 0 then true else false end from Entity e where e.property = ?1 -- here go your conditions