JPA Repository Query on additional table #ManytoMany - spring-data-jpa

Question

I want to do select like this in my jpa spring repository
SELECT sicknes_id, count(symptomp_id) as ilosc FROM symptomp_sicknes where symptomp_id IN (1,2) group by sicknes_id Order by ilosc DESC;
My enitity
#Entity
#Table(name = "symptomp")
public class Symptomp {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "symptomp_id")
private Long symptomp_id;
#Column(name = "name")
private String name;
#Column(name = "description")
private String description;
#ManyToMany(cascade = {CascadeType.DETACH,CascadeType.MERGE,CascadeType.PERSIST,CascadeType.REFRESH}, fetch = FetchType.LAZY)
#JoinTable(name = "symptomp_sicknes",joinColumns = #JoinColumn(name = "symptomp_id"),inverseJoinColumns = #JoinColumn(name = "sicknes_id"))
private Set<Sicknes> sicknes = new HashSet<>();
#Entity
#Table(name = "sicknes")
public class Sicknes {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
#Column(name = "sicknes_id")
private Long sicknes_id;
#Column(name = "name")
private String name;
#Column(name = "description")
private String description;
#ManyToOne(cascade = {CascadeType.DETACH,CascadeType.MERGE,CascadeType.PERSIST,CascadeType.REFRESH}, fetch = FetchType.LAZY)
#JoinColumn(name = "speciesId")
private Species species;
My Symptomp repository:
public interface SymptompRepository extends JpaRepository<Symptomp, Long> {
#Query("select p from Symptomp p where name like ?1%")
public List<Symptomp> findAllBySymptompName(String symptomp);
public Symptomp findByName(String symptomp);
public List<Symptomp> findByNameIn(List<String> list);
Integer countDistinctSymptompByName(String id);
}
How I can create this select in my JPA repository?
I try get value like in select but i got error mapping bean.

Answer 1

You can get query result as List<Object[]> using nativeQuery=true parameter
#Query("SELECT sicknes_id, count(symptomp_id) as ilosc FROM symptomp_sicknes where symptomp_id IN (1,2) group by sicknes_id Order by ilosc DESC", nativeQuery=true)
List<Object[]> getQueryResult();
Other option is to create dto class with appropriate constructor
public class QueryResultDto {
Long sicknesId;
Long count;
public QueryResultDto(Long sicknesId, Long count) {
this.sicknesId = sicknesId;
this.count = count;
}
}
Then using JPQL
#Query("select new yourproject.dtopath.QueryResultDto(...")
List<QueryResultDto> getQueryResult(#Param("symptompIds") List<Long> symptompIds);

Answer 2

If you want to avoid a native Query the best way is to create an Entity for that JoinTable. Then you can query it easily. Additional benefit if this is that if in future a requirement will pop up that you have to store additional attributes in that relation you will have the Entity already there to do that easily.