Spring Data JPA + Kotlin

Question

In Spring Data JPA trying to use interface projection technique:

interface DocInfoShort {
    var docTypeId: Int
}

And my DAO:

public interface DocRepository extends JpaRepository<Doc, Long> {
    @Query("select sum(cast(doc.isSent AS int)) as docTypeId" +
            "       from Doc doc group by docTypeId", nativeQuery = true)
    fun someQuery(): List<DocInfoShort>
}

but it is not working:

could not extract ResultSet; SQL [n/a]; nested exception is org.hibernate.exception.SQLGrammarException: could not extract ResultSet"

How can i fix it.

Answer 1

Just make DocInfoShort a class with a proper constructor and use the constructor syntax of JPQL in the query annotation:

@Query("select new full.package.name.DocInfoShort(sum(cast(doc.isSent AS int)))" +
       "from Doc doc group by docTypeId")