How to use GroupBy with Spring JPA Specifications (JPA Specification Executor)

Question

I'm looking for a way to use multiple (or at least one) group by in my JPA Specifications. I've found that i can put, for example:

cq.groupBy(root.get("id"));

in my specification but the problem is that JpaSpecificationExecutor doesn't have proper interface to support this aggregation as there is no method that returns a Map nor there is a possibility to have my own DTO as a return type (as far as i know).

Answer 1

The Specification interface is only intended for specifying WHERE-clauses. If you wan't to specify GROUP BY or anything else affecting the columns selected as opposed to the rows selected you should write a custom method to meet your needs.