CMP and BMP entity beans can declare home methods that perform operations related to the EJB component but that are not specific to an entity bean instance. A home method must have a matching implementation in the bean class with the signature ejbHome< METHOD-NAME >( ).

For example, the Cruise EJB might define a home method that calculates the total revenue in bookings for a specific Cruise:

public interface CruiseHomeLocal extends javax.ejb.EJBLocalHome {

    public CruiseLocal create(String name, ShipLocal ship);
    public double totalReservationRevenue(CruiseLocal cruise);

}

Every home method declared by the home interfaces must have a corresponding ejbHome< METHOD-NAME >( ) in the bean class. For example, the CruiseBean class would have an ejbHomeTotalReservationRevenue( ) method, as shown in the following code:

public abstract class CruiseBean implements javax.ejb.EntityBean {
    public Integer ejbCreate(String name, ShipLocal ship) {
        setName(name);
    }
    ...
    public double ejbHomeTotalReservationRevenue(CruiseLocal cruise) {

        Set reservations = ejbSelectReservations(cruise);
        Iterator it = reservations.iterator( );
        double total = 0;
        while(it.hasNext( )) {
            ReservationLocal res = (ReservationLocal)it.next( );
            total += res.getAmount( );
        }
        return total;

    }
 
   public abstract ejbSelectReservations(CruiseLocal cruise);
   ...
}

The ejbHome( ) methods execute without an identity within the instance pool. This is why ejbHomeTotalReservationRevenue( ) required that a CruiseLocal EJB object reference be passed in to the method. This makes sense once you realize that the caller is invoking the home method on the entity bean’s EJB home object and not an entity bean reference directly. The EJB home (local or remote) is not specific to any one entity identity.

The bean developer may implement home methods in both bean-managed and container-managed persistence implementations. The ejbHome( ) methods of CMP entities typically rely on ejbSelect( ) methods, while the ejbHome( ) methods of BMP implementations frequently use direct database access and find methods to query data and apply changes.