Hibernate annotation equivalent of ?

Question

I'm migrating an old application using xdoclet to Hibernate 4 with annotations. I'm having a problem translating the "hibernate.properties" xdoclet tag (which generates as <properties unique="false".../>; in .hbm.xml) to equivalent annotations. Based on Hibernate's JIRA, it looks like a @Properties annotation was never created when Hibernate annotations were created, and is still being mulled over as a possible enhancement in Hibernate 5.

Here's how the application is using <properties>. A properties group is set up as follows:

/**
 * @hibernate.class table="ENTITY_A" dynamic-update="true" dynamic-insert="true"
 * @hibernate.properties name="b_plus_c_group" 
 */
public class ClassA {
    private ClassB b;    
    private ClassC c;
    ...

    /** 
     * @hibernate.many-to-one 
     *    column="COL_B"
     *    class="com.acme.ClassB"
     *    cascade="none"
     *    properties-name="b_plus_c_group"
     */
    ClassB getB() {
        return b;
    }

    /** 
     * @hibernate.many-to-one 
     *    column="COL_C"
     *    class="com.acme.ClassC"
     *    cascade="none"
     *    properties-name="b_plus_c_group"
     */
    ClassC getC() {
        return c;
    }
}

The "b_plus_c_group" is then used in another entity to express a join to ClassA using b and c as keys:

/**
 * @hibernate.many-to-one
 *    property-ref="b_plus_c_group"
 *    insert="false"
 *    update="false"
 *    cascade="all"
 *    fetch = "join"
 *    class="com.acme.ClassA"
 * @hibernate.formula value="COL_B"
 * @hibernate.formula value="COL_C"
 */
ClassA getA() {
    return a;
}

Some business logic also references the properties group when constructing a Criteria query:

Criteria criteria = session.createCriteria(ClassA.class, "a");
criteria
.createAlias("b_plus_c_group", "bpc")
.createAlias("bpc.b", "b")
.createAlias("bpc.c", "c")
.add(Restrictions.eq("c.keyField", keyForC))
.setProjection(
    Projections.projectionList()
    .add(Projections.property("a.description"))
    .add(Projections.property("b.description")));

(Note: unfortunately, a test environment does not exist for the xdoclet-based implementation currently in production, so I can't easily run scenarios to see how these queries actually behave. At this point I'm dependent on manual observation.)

My summary of the usage here is: we have a pair of properties "b" and "c" that together form a non-unique key for A (unique="false" is the default). So we give that pair of properties the name "b_plus_c_group" and use it:

1. as the key for a many-to-one relation to A from another entity
   • but how can a non-unique pair of keys dependably yield the single result required by a many-to-one? And what additional role is played by the inclusion of formulas consisting of COL_B and COL_C?
2. as a way to get the fields in the group to express a Restriction and a Projection for a query.
   • but can't these be expressed as simply "a.b" and "a.c"?

So I have two usages that look faulty to me (but I could be missing something), and no way to just translate those over to annotations verbatim.

Can anyone clarify the expected behavior and offer a way to express as annotations?