Question

I want to make a criteria query that has the same behaviour as the following SQL query:

SELECT Count(*)
FROM Datagathering_respuestas, Datagathering
WHERE Datagathering.document = 4 AND Datagathering.id_datagathering = datagathering_respuestas.id_datagathering
GROUP BY respuesta;

it is all around the following class:

public class DataGathering {
    private int id;
    private Usuario user;
    private Date fecha;
    private int individual;
    private DataDocument document;
    private List<String> respuestas;

and it’s corresponding mapping file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="pe.com.abf.pws.clases.DataGathering">
    <id column="id_datagathering" name="id">
      <generator class="identity"/>
    </id>
    <many-to-one class="pe.com.abf.pws.clases.DataDocument" name="document"/>
    <many-to-one class="pe.com.abf.pws.clases.Usuario" name="user"/>
    <property name="individual"/>
    <property name="fecha" type="timestamp"/>
    <list name="respuestas">
      <key column="id_datagathering"/>
      <index column="idx_respuesta"/>
      <element column="respuesta" length="4000" type="string"/>
    </list>
  </class>
</hibernate-mapping>

my main problem here is that the grouping property “respuestas” is defined as a list of element of type string and doesn’t have it’s own class. In SQL it’s easy to just reference to the corresponding table, but in Criteria, I have no idea how to reference to the elements to group by them. I have managed to get this query:

        Criteria c = s.createCriteria(DataGathering.class);
        c.add(Restrictions.eq("document.id", id));
        c.createCriteria("respuestas","resp");
        c.setProjection(Projections.projectionList().add(Projections.rowCount()));

which has the same behaviour as the above SQL query but without the group by element, so I think I am near. The problem is again that I don’t know how to refer to the values inside “respuestas”.

Any Idea how I can complete my query? any help will be highly appreciated.

Answer 1

I managed to do this by doing the following:

da = s.createCriteria(DataGathering.class)
        .add(Restrictions.eq("document.id", id))
        .createCriteria("respuestas","resp")
        .setProjection(Projections.projectionList()
                .add(Projections.groupProperty("resp.elements").as("resp"))
                .add(Projections.count("resp.elements").as("amount")))
        .setResultTransformer(Transformers.aliasToBean(EncuestaHelper.class))
        .list();

The trick is that Criteria uses the key "elements" to refer to a plain element collection. Then, giving the projections alias that match with the properties of an special class you can easily make a list of that class to use it on reports.

Thanks to anyone who tried to help