Hi,

how can I query a table that is not a "mapped entity" through JPA Hibernate?
(there is no POJO annotated with @entity for that table)

I tried entityManager.createNativeQuery(mySQLString). No exception is thrown but I have no idea what type the objects in the returned list have (getResultList()).

simply look
usually List<Object[]>

An Object of type "Object" usually isn't that helpful if I'm interested as Example in an Integer value. I'm more interested in the "real" type. So is an integer column returned as a java Integer? or a java.sql type? -> must be casted.
So questions: is it possible at all?
and if yes what types to cast the returned objects to?

/**
* Interface for all result extractors.
*/
interface ResultExtractor<T> {
public T getResult(List resultSet);
}


/**
* Extractor for single integer result. You have to set number of needed
* column in the result set row.
*/
class IntegerExtractor implements ResultExtractor<Integer> {
private final Integer numberOfColumn;

public IntegerExtractor(int numberOfColumn) {
this.numberOfColumn = numberOfColumn;
}

public Integer getResult(List resultSet) {
if (0 < resultSet.size()) {

if (resultSet.get(0) instanceof List) {
// toplink
Object value = resultSet.get(0);
if (value instanceof List) {
return Integer.valueOf(((List) value).get(numberOfColumn).toString());
} else {
return Integer.valueOf(value.toString());
}
} else if (resultSet.get(0).getClass().isArray()) {
// hibernate
Object value = ((Object[]) resultSet.get(0))[numberOfColumn];
return Integer.valueOf(value.toString());
} else {
Object value = resultSet.get(numberOfColumn);
return Integer.valueOf(value.toString());
}
}
return null;
}
}


/**
* abstract DAO method
*/
<T> T findByNativeQuery(final String queryString, ResultExtractor<T> resultExtractor) {
Query query = entityManager.createNativeQuery(queryString);
return resultExtractor.getResult(query.getResultList());
}




and use

Integer result = dao.findByNativeQuery("select num from table", new IntegerExtractor(0));