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JPA NamedQuery Result [message #503061]

Thu, 10 December 2009 17:54

Larry

Messages: 30
Registered: December 2009

Member

Sorry if this is easy question, new to JPA!

I would like to create a named query that returns only a few fields of an Entity.

Something like this "select emp.name,emp.id from Employee emp".

I would like to get back an instance on Employee with just those fields filled in. Is this possible?? It seems pretty cumbersome to have to use "List<Object[String,int]>" .

Thanks for the help.

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Re: JPA NamedQuery Result [message #503107 is a reply to message #503061]

Thu, 10 December 2009 21:17

Doug Clarke

Messages: 155
Registered: July 2009

Senior Member

You can use a FetchGroup to specify the attributes you want loaded. The entity will then load the rest of its state upon demand.

public List<Employee> fetchGroupExample(EntityManager em) {
Query query = em.createQuery("SELECT e FROM Employee e ORDER BY e.id");

FetchGroup fetchGroup = new FetchGroup();
fetchGroup.addAttribute("id");
fetchGroup.addAttribute("firstName");
fetchGroup.addAttribute("lastName");

query.setHint(QueryHints.FETCH_GROUP, fetchGroup);

return query.getResultList();
}

Doug

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