JPA native query join returns object but dereference throws class cast exception

Question

I\'m using JPQL Native query to join table and query result is stored in List.

public String getJoinJpqlNativeQuery() {



              


        

Answer 1

The SELECT clause queries more than one column or entity, the results are aggregated in an object array (Object[]) in the java.util.List returned by getResultList( ).

 //---

    Query query = manager.createQuery("SELECT v1.bitbit, v1.numnum, v1.someTime, t1.username, t1.anotherNum FROM MasatosanTest t1 JOIN MasatoView v1 ON v1.username = t1.username;");

    List results = query.getResultList( ); // Fetches list containing arrays of object
    Iterator it = results.iterator( );

    while (it.hasNext( )) {

       Object[] result = (Object[])it.next(); // Iterating through array object 

       Boolean first = (Boolean) result[0]; // Fetching the field from array

       /* Likewise for all the fields, casting accordingly to the sequence in SELECT query*/

    }

    //---

Edit : To avoid casting explicitly, you can go for constructor expression, adding a constructor to the entity with appropriate arguments.

SELECT new org.somepackage.XEntity(x.a, x.b) FROM XEntity x

Answer 2

I'm not familiar with JPQL Native query, but you simply debug with:

Object o = out.get(0); System.out.println(o.getClass());

Then work from there. If it's a vector, iterate through and find what's in the vector.