How to check a collection size in JPA2

Question

Consider the following:

@Entity
public class Book 
{ 
    private List authors;
    @ElementCollection
    public List getAuthors         


        

Answer 1

In JPQL:

select b from Book where size(b.authors) >= 2

Using the criteria API (but why would you replace such a simple static query with the following mess?):

CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Book> criteriaQuery = cb.createQuery(Book.class);
Root<Book> book = criteriaQuery.from(Book.class);
Predicate predicate = cb.ge(cb.size(book.get(Book_.authors)), 2);
criteriaQuery.where(predicate);
criteriaQuery.select(book);