IllegalArgumentException: Mismatch in requested result type

I get following error:

IllegalArgumentException: Mismatch in requested result type [com.taqwaapps.entity.Event] and actual result type [com.taqwaapps.dto.EventDTO]

But my code points to the type I intent to receive:

@Repository
public class EventRepositoryImpl  {

    @PersistenceContext
    private EntityManager entityManager;

    public List<EventDTO> getLatestEventsFiltered(String sql, int limit) {
        Query query = entityManager.createQuery(sql, Event.class);
        query.setMaxResults(limit);

        List<EventDTO> resultList = (List<EventDTO>) query.getResultList();
        return resultList;
    }
}

Info: The objects Event and EventDTO are different.

Any Idea?

CodePudding user response：

Query query = entityManager.createQuery(sql, Event.class); <---- Here you inform the library that it must parse the result using Event.class

But here List<EventDTO> resultList = (List<EventDTO>) query.getResultList(); you try to parse the result using EventDTO.class

Change it into List<Event> resultList = query.getResultList();

and then use some converter to convert the List<Event> into a List<EventDTO>

CodePudding user response：

Before fixing your code you must be clear about the reasons for java.lang.IllegalArgumentException. Refer

Reasons for java.lang.IllegalArgumentException

When Arguments out of range. For example, the percentage should lie between 1 to 100. If the user entered 101 then an IllegalArugmentExcpetion will be thrown.
When argument format is invalid. For example, if our method requires date format like YYYY/MM/DD but if the user is passing YYYY-MM-DD. Then our method can’t understand then IllegalArugmentExcpetion will be thrown.
When a method needs non-empty string as a parameter but the null string is passed.

Once you are clear about the issues, please refer to the solution which was already provided by @Panagiotis Bougioukas

Issue - Argument format is invalid

Most probably below solution should work(Not tested)

@Repository
public class EventRepositoryImpl {

    @PersistenceContext
    private EntityManager entityManager;

    public List<EventDTO> getLatestEventsFiltered(String sql, int limit) {

        var query = entityManager.createQuery(sql, Event.class);
        query.setMaxResults(limit);
        var resultList = query.getResultList().
                 stream().map(this::convertToDto).
                    collect(Collectors.toList());

        return resultList;
    }

    private EventDTO convertToDto(Event event) {
        var dto = new EventDTO();
        // convert event to eventdto here
        return dto;
    }
}