休眠：搜索在一组枚举中包含值的实体

Question

I have an entity similar to the following example:

@Entity
@Table(name = "AIRPLANE")
public class Airplane {

    @ElementCollection(targetClass = Color.class, fetch = FetchType.LAZY)
    @CollectionTable(name = "AIRPLANE_COLORS", joinColumns = @JoinColumn(name = "AIRPLANE_ID"))
    @Column(name = "AIRPLANE_COLOR")
    @ForeignKey(name = "FK_AIRPLANE_COLOR_ID")
    @Enumerated(EnumType.STRING)
    private Set<Color> colors;    
    ...
}
...
public enum Color {
    WHITE, RED, BLUE
}

Where colors is a Set of enums, and I want to make a search for all entities Airplanes that contains the color RED in this set.

Can I make that with Criterias or should I use HQL queries?

Thanks!

Answer 1

The criteria API is useful to create queries based on a dynamic set of... criteria. For a static query, HQL is always more readable:

select a from Airplane a where :color member of a.colors

or

select a from Airplane a join a.colors color where color = :color

should do the trick

Answer 2

As suggested by JB Nizet, you can use HQL to get the results:

        Query query = session.createQuery("from Airplane as airplane inner join "
                + "airplane.colors colors where colors =:color");
        query.setParameter("color", Color.BLUE);

        List<Airplane> list = query.list();
        for (Airplane airplane : list) {
            System.out.println("->" + airplane.getColors());
        }

Answer 3

There is a way to perform such query using Criteria in Hibernate. You just have to join colors and ask for its elements property (ie colors.elements ).

elements is a keyword defined in Hibernate's CollectionPropertyNames class and you can access your enum value using it.

session.createCriteria(Airplane.class)
    .createAlias("colors", "colors")
    .add(Restrictions.eq("colors.elements", Color.BLUE))
    .list()