Is it possible to make use of 2nd level cache when querying foreign keys

Question

afaik entities are indexed just by their primary key in the 2nd level cache, so querying related entities won't make use of it:

@Entity
public class Employee {
    @Id
    @Column(name="EMP_ID")
    private long id;
    ...
    @OneToMany(mappedBy="owner")
    private List<Phone> phones;
    ...
}
@Entity
public class Phone {
    @Id
    private long id;    
    ...
    @ManyToOne
    @JoinColumn(name="OWNER_ID")
    private Employee owner;
    ...
}

EntityManager em;

// uses 2nd level cache
Employee employee = em.find(Employee.class, 1); 

// doesn't use 2nd level cache. Even if 2nd level cache actually 
// contains all referenced phones, there will be a DB call.
employee.getPhones();

Is it possible to avoid the db call, when accessing phones and make use of the 2nd level cache? Is there a cache implementation supporting custom indexing?

I'm currently using wildfly 14 with hibernate/infinispan.

Will accessing phones at least make use of query cache or just em.createQuery(...)?

Answer 1

I finally found a solution. There is a collection cache in Hibernate which has to be explicitly enabled by annotating the collection with org.hibernate.annotations.Cache.

@Entity
@Cacheable(true)
public class Employee {
    @Id
    @Column(name="EMP_ID")
    private long id;
    ...
    @Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
    @OneToMany(mappedBy="owner")
    private List<Phone> phones;
    ...
}

It works perfectly!