JPA 2.0 native query results as map

Question

I run a JPA 2.0 native query like this:

Query query = em.createNativeQuery("SELECT NAME, SURNAME, AGE FROM PERSON");
List list = query.getResultList();

now list has all the rows returned by the query. I can iterate over them, but every entry is an Object[] where:

• at index 0 I find NAME
• at index 1 I find SURNAME
• at index 3 I find AGE

Did anyone find a way to do something like this:

Map<String, Object> row = list.get(index);
String name = row.get("NAME");
String surname = row.get("SURNAME");
Integer age = row.get("AGE");

I would need this since the native query that I execute is a dynamic one and I don't know the order of the field in SELECT clause, so I don't know id the query will look like:

SELECT SURNAME, NAME, AGE FROM PERSON

or

SELECT AGE, NAME, SURNAME FROM PERSON

or even

SELECT AGE, SURNAME, NAME FROM PERSON

Answer 1

Which JPA are you using - Hibernate, EclipseLink or something else?

There is no standard way to do this in JPA but your specific implementation may allow it - for example, Eclipselink has a query result type hint.

http://dev.eclipse.org/mhonarc/lists/eclipselink-users/msg03013.html

Query query = entityManager.createNativeQuery(sql);
query.setHint(QueryHints.RESULT_TYPE, ResultType.Map);

For Hibernate, with javax.persistence.Query dbQuery:

org.hibernate.Query hibernateQuery =((org.hibernate.jpa.HibernateQuery)dbQuery)
.getHibernateQuery();
hibernateQuery.setResultTransformer(AliasToEntityMapResultTransformer.INSTANCE);

Answer 2

As other already mentioned, older JPA does not support it, however I have workaround solution with Postgres 9.4 in my situation, while working with Jackson,

List<String> list = em.createNativeQuery("select cast(json_object_agg(c.config_key,c.config_value) as text) from myschema.configuration c")
                   .getResultList();

To use it in Bean layer use below method, otherwise directly return.

//handle exception here, this is just sample
Map map = new ObjectMapper().readValue(list.get(0), Map.class);

Few more json functions, https://www.postgresql.org/docs/9.4/static/functions-json.html. I am sure you can find same for other databases.

Answer 3

Take a look on this I got it when working on project that I could not use all JPA features so I tried the traditional jdbc method even if I would not recommend this but it's working for me.

@LocalBean
public class TCotisationEJB {

    @PersistenceContext(unitName="ClaimsProjectPU")
    private EntityManager em;

    @TransactionAttribute(TransactionAttributeType.NEVER)
    public List getCotisation(){
        Query query=em.createNativeQuery("select Annee,Mois,RetSonarwa from TCotisMIFOTRA2008 where matricule='10000493' order by Annee");
        List<Object[]> cotisation=query.getResultList();
        Object[] cotisationData;

         for(int i=0;i<cotisation.size();i++){
              cotisationData=cotisation.get(i);

             System.out.print("Annee: "+cotisationData[0]+" Mois :"+cotisationData[1]+" Amount       :"+cotisationData[2]+"\n");

     }  
     return query.getResultList();
     }    
}