CODEWITHSUNDEEP
java-8spring-data-rest
nader.h
nader.h

Reputation: 505

select distinct values using spring data rest

I'm using java 8 and spring-data-rest to create API on my data.

I have a table Car(id, name, date...)

I'm trying to have an endpoint to retrieve distinct car names.

here's my Repository : 

@RepositoryRestResource(path = "cars")    
public interface CarRepository extends JpaRepository<Car, Long> {
    //What i want to do
    //@Query(value = "select distinct c.name as name from Car c")
    @Query(value = "select distinct c from Car c")
    List<Car> findDistinctName();      
}

The query commented does not work , i have an exception 

java.lang.IllegalArgumentException: PersistentEntity must not be null!

apparently this is the normal behavior of SDR.

I tried another solution by using Projections

@Projection(name = "name", types = {Car.class})
public interface CarName {
    String getName();
}

but i cant get the distinct values, any idea?

Thank you :)

Upvotes: 1

Views: 1525

Answers (3)

Christian Oliver
Christian Oliver

Reputation: 142

I think you should remove the @Query annotation. Just List<Car> findDistinctName(); or List<Car> findNameDistinct(); should suffice. It will automatically generate the query select c.name from Car c

Upvotes: 0

nader.h
nader.h

Reputation: 505

I found an (ugly) workaround, using jpql :

@Query(value = "select c from Car C WHERE c.id IN (SELECT min(ca.id) FROM Car ca Group by ca.name)")

Upvotes: 0

Cepr0
Cepr0

Reputation: 30289

All you need, to do if you need a distinct list of cars, is such this query method:

public interface CarRepository extends JpaRepository<Car, Long> {
    List<Car> findDistinctBy();
}

Spring Data JPA supports the Distinct keyword in repository query methods to set a distinct flag on the query to be created.

Upvotes: 1

Related Questions