JPA Native Query select and cast object

You might want to try one of the following ways:

• Using the method createNativeQuery(sqlString, resultClass)

  Native queries can also be defined dynamically using the EntityManager.createNativeQuery() API.

  String sql = "SELECT USER.* FROM USER_ AS USER WHERE ID = ?";
  
  Query query = em.createNativeQuery(sql, User.class);
  query.setParameter(1, id);
  User user = (User) query.getSingleResult();
  

• Using the annotation @NamedNativeQuery

  Native queries are defined through the @NamedNativeQuery and @NamedNativeQueries
  annotations, or <named-native-query> XML element.

  @NamedNativeQuery(
      name="complexQuery",
      query="SELECT USER.* FROM USER_ AS USER WHERE ID = ?",
      resultClass=User.class
  )
  public class User { ... }
  
  Query query = em.createNamedQuery("complexQuery", User.class);
  query.setParameter(1, id);
  User user = (User) query.getSingleResult();
  

You can read more in the excellent open book Java Persistence (available in PDF).

^{───────
NOTE: With regard to use of getSingleResult(), see Why you should never use getSingleResult() in JPA.}