I need to fetch 6 columns by joining 3 different tables. I have declared them as NamedNativequery on top of the entity class and I have used create named query method form JPA. When I try fo fetch the result set i get the list of array objects instead of the List of objects of POJO type. is there any external mapping should I be defining in order to map the result set to an external POJO?
You certainly can. This should help:
@NamedNativeQuery(query = "SELECT t1.col1, t2.col2 FROM t1 JOIN t2 ON ...", name = "MyNamedQuery", resultSetMapping = "MyPojoMapper")
@SqlResultSetMapping(name = "MyPojoMapper", classes = @ConstructorResult(
targetClass = MyPojo.class,
columns = {
@ColumnResult(name = "col1", type = String.class),
@ColumnResult(name = "cols", type = String.class)
}))
Then use it as such:
NativeQuery query = session.getNamedNativeQuery("MyNamedQuery");
MyPojo result = (MyPojo) query.getSingleResult();
You can use projection to specify what properties you want to get
https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#projections
or directly get with JPQL:
@Repository
public class CustomRepositoryImpl {
@Autowired
private EntityManager entityManager;
public List<Dto> find() {
var query = "SELECT new Dto(
x.Field1,
y.Field2,
z.Field3,
...)
FROM XxxEntity x
LEFT JOIN YyyEntity y
LEFT JOIN ZzzEntity z"
var jpqlQuery = entityManager.createQuery(query);
return jpqlQuery.getResultList();
}
}
public class Dto {
// Must have parameterized constructor with all fields what used in Repository
public Dto(int field1, String field2, String field3, ...) {
}
}
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