Java Hibernate NamedQuery resultTransformer

Question

i have this query with NamedQuery using Hibernate this is my sample code.

NamedQuery

@NamedQuery(name="com.company.generic.model.Student.getByID()",query="select name from com.company.generic.model.Student where id=:id")

Java Code

private Student getStudentNameById(Integer id)
{
    final Session session = ....
    final Query query = session.getNamedQuery("com.company.generic.model.Student.getByID()")
    .setParameter("id",id)
    .setResultTransformer(Transformers.aliasToBean(Student.class));
    final Student student = (Student)query.uniqueResult();
    return student;
}

when the query returns all the columns the resultTransformerworks OK but when i return only a few columns returns

Exception in thread "main" org.hibernate.PropertyNotFoundException: Could not find setter for 0 on class com.company.generic.model.Student

my questions are

1). why works with all columns but not working with a few or only a column.

2). which is the diff between namedQuery and Criteria using resultTransformer should namedQuery have setProjection?

3). must i write my own transformer? any workaround...?

thanks a lot...

Answer 1

question #1:
Most probably you need to add alias to name field in select list

select s.name as name from com.company.generic.model.Student s where s.id=:id

so Hibernate can find the setName(String) method in Student.class.
Using criteria the equivalent is

session.createCriteria(Student.class)
 .add(Restrictions.eq("id",id))
 .setProjection(Projections.property("name").as("name"))
 .setResultTransformer(Transformers.aliasToBean(Student.class));

question #2:
Named query select list is the projection.

question #3:
see answers above