Hibernate count rows with some criterias

Question

Suppose I have a table Person and i want to count all those people whose "birthDate" is not null and they are a student. Assuming i have two columns :

birthDate Date (can be null)
isStudent boolean (default: false)

How can i do this using hibernate.. ?

Answer 1

Criteria crit = session.createCriteria(Person.class);
crit.add( Restrictions.isNotNull("birthDate"));
crit.add( Restrictions.eq("isStudent", true));
crit.setProjection(Projections.rowCount());
Integer count = (Integer)crit.uniqueResult();

Answer 2

Criteria crit = session.createCriteria(Person.class);
crit.add( Restrictions.isNotNull("birthDate"));
crit.add( Restrictions.eq("isStudent", true));
List<Person> students = crit.list();
Integer count = students.size();

or if just want a single count value, and no list returned :

Criteria crit = session.createCriteria(Person.class);
crit.setProjection(Projections.rowCount());
crit.add( Restrictions.isNotNull("birthDate"));
crit.add( Restrictions.eq("isStudent", true));
return (Long) crit.uniqueResult();