Populating JComboBox with TypedQuery does not show Entitys name correct

Question

I want get the name of each object in this return list, but the output is an array of Object[], and this show entitys.Categoria[id=1] in my JComboBox control.

I not understand this. Please help me! This is my code:

public List<Categoria> consultarCategorias() {
    try {            
        TypedQuery<Categoria> q = 
                em.createQuery("select c from Categoria c", Categoria.class);
            List<Categoria> results = q.getResultList();            
            return results;
    } catch (Exception e) {
        return null;
    }
}

Note: I use this

for (Categoria c : results) {
   System.out.println(c.getName());
}

and not work, this show the result cannot convert to Categoria

This is the code to fill my JComboBox:

public void fillCmbCategorias() {
   cmbCategoria.removeAllItems();
   try {
      Object[] listaCategorias = crud.consultarCategorias().toArray();
      DefaultComboBoxModel dcb = new DefaultComboBoxModel(listaCategorias);
      cmbCategoria.setModel(dcb);
   } catch (Exception e) {
      JOptionPane.showMessageDialog(null
              ,"No se pudo cargar la lista de categorias. " + e.getMessage());
   }
}

So is `results` obtained like `List results = consultarCategorias()`? What is the actual error and where do you see it? Can you paste the part of code from the context you declare List? — pirho, Oct 26 '17 at 07:01
Or is the error actually when you run `consultarCategorias()` and there `q.getResultList();`? — pirho, Oct 26 '17 at 07:23
Yes, the results obtained as objects: I invoke that method from JFrame: this is the code to fill my JComboBox : — Mateo Rodríguez, Oct 26 '17 at 17:09
Object[] listaCategorias = crud.consultarCategorias().toArray(); DefaultComboBoxModel dcb = new DefaultComboBoxModel(listaCategorias); cmbCategoria.setModel(dcb); — Mateo Rodríguez, Oct 26 '17 at 17:21

score 0 · Answer 1 · answered Oct 26 '17 at 06:58

0

Can you try casting like this :

List<Categoria> results = (List<Categoria>)q.getResultList();  `

answered Oct 26 '17 at 06:58

hiren

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pirho · Accepted Answer · 2017-10-26T18:13:44.220

Only reason i can imagine that you have declared the result as some super type list, like List<?> or List<Object>.

Assuming you can assing the return value of consultarCategorias() to it.

And of course you should not do it this way - you should correct the list generic type - but this might then work:

for (Object c : results) {
   System.out.println(((Categoria)c).getName());
}

Update (after problem code added):

Your problem seems be this:

Object[] listaCategorias = crud.consultarCategorias().toArray();

as i suspected.

Try

Categoria[] listaCategorias =
   crud.consultarCategorias().toArray(new Categoria[]{});
// toArray() needs some array instance to determine the type

About Lists and converting to Arrays see more here Convert list to array in Java

Populating JComboBox with TypedQuery does not show Entitys name correct

2 Answers2