Return List of entity instead of List of object

Question

Eclipse / Java

I have a method to perform database query.

myBean :

List<Composicao> itemProdutoLista = compPrecoServico.buscar(Composicao.nomeQuery);

The nomeQuery is :

@NamedQuery(name = "nomeQuery", query= " SELECT composicao.valortotal,composicao.id FROM Composicao composicao

query - javax.persistence.query

public List<T> buscar(String nomeQuery) {
    Query query = entityManager.createNamedQuery(nomeQuery);
    return query.getResultList();
}

My return List buscar get me that : An Object elementData

enter image description here

How can I get an Entity Composicao elementdata in my return buscar method ? instead of object elementData

@JB Nized thats it what I want regarding that last post about How to read Java ArrayList sub-items — Al2x
– Al2x, Commented Feb 14, 2014 at 12:35
I don't quite understand - List<Composicao> itemProdutoLista contains objects of type Composicao so which part of your code is incorrect? — Smutje
– Smutje, Commented Feb 14, 2014 at 12:40
see my printscreen. It gets me an Object elementData and I need an entity elementData — Al2x
– Al2x, Commented Feb 14, 2014 at 12:41
So when you iterate over itemProdutoLista you get Object? But your list is already correctly typed, so when the type would not match, you would get a ClassCastException most likely. — Smutje
– Smutje, Commented Feb 14, 2014 at 12:44

JB Nizet · Accepted Answer · 2014-02-14 12:46:46Z

3

I gave you the query to use in your previous question:

SELECT composicao FROM Composicao composicao

Don't you understand that selecting two fields of an entity, as you're doing in the query

SELECT composicao.valortotal,composicao.id FROM Composicao composicao
                    ^-- first field      ^-- second field

doesn't return Composicao objects, but simply the two fields you selected: valortotal and id?

You're explicitely asking JPA to return only valortotal and id. Why would it return all the other fields and create a Composicao object? You want all the fields, and not just valortotal and id. So the query is (I'll repeat it a third time just in case):

SELECT composicao FROM Composicao composicao

answered Feb 14, 2014 at 12:46

JB Nizet

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13 Comments

Al2x Over a year ago

we are back to that old question. I need to retrieve itemProdutoLista.get(0).get(0) for valorTotal and itemProdutoLista.get(0).get(1) for id. I know thats not exists get(x).get(y) but is what I need to @JB Nizet

JB Nizet Over a year ago

Composicao firstComposicao = itemProdutoLista.get(0); int valortotal = firstComposicao.getValortotal(); Long id = firstComposicao.getId();

. If you get back a List<Composicao>, every element of the list is a Composicao. Isn't that obvious?

Al2x Over a year ago

I did it already but I got this : java.math.BigDecimal cannot be cast to br.com.getsprint.gestao360.entidade.Composicao @JB Nizet

JB Nizet Over a year ago

You're talking about an exception caused by code you're not showing. And this exception is thrown because you're trying to cast a BigDecimal to ComposicaoPreco. BigDecimal is not a ComposicaoPreco, so that doesn't make any sense. That's like doing Banana b = (Banana) truck; A truck is not a banana. And casting it to Banana won't change anything to what a truck is: it's a truck and will always be a truck. So of course, you get a ClassCastException.

Al2x Over a year ago

I got exception in this line you posted : Composicao firstComposicao = itemProdutoLista.get(0); theres no code to show. I pasted all my code in this post. and itemProdutoLista is printed in this post either

|

Edwin Dalorzo · Accepted Answer · 2014-02-14 12:47:04Z

0

Assuming you are talking about something like JPA.

Put a constructor on your entity (besides the empty/default constructor) that accepts every one of your query arguments.

@Entity
public class Jedi
   @Id private int id;
   private String name;

   //required by the standard
   public Jedi(){}

   public Jedi(int id, String name) {
     this.id = id;
     this.name = name;
   }

   //...
 }

Then your query

select NEW org.starwars.Jedi(j.id,j.name) from Jedi j where name.endsWith('Sky Walker')

answered Feb 14, 2014 at 12:47

Edwin Dalorzo

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