The JAIN SLEE specification defines that an SBB child relation requires:

  • an abstract get child relation method declared in the SBB abstract class; and

  • a <get-child-relation-method> deployment descriptor entry that binds the get child relation method to a particular SBB type.

The get child relation method returns a ChildRelation object, which the SBB developer uses to create, remove, or manage the SBBs in the child relation.

A difficulty with this approach is that child relations cannot be added to an SBB without code changes to the SBB abstract class. For example, consider an SBB that delegates call processing to different child SBBs based on the protocol in use for the call (CAPv2, CAPv3, ETSI INAP CS1, and so on). Since the child SBB for each protocol needs its own get child relation method in the SBB abstract class, it’s not easy to decide at build time what protocols will be supported without modifying the SBB abstract class and recompiling. Code changes are also extremely undesirable when service bindings are used to change the child relationships of the SBB after the SBB has been installed in the SLEE.

Rhino provides an alternative mechanism to declare and use SBB child relations, which eliminates the recompilation part of the build cycle in these types of use cases. Child relations are still declared in the deployment descriptor, but the SBB accesses the child relations using a Child Relation Facility provided by the SLEE.

Extended child relation declarations

Rhino allows an SBB to declare a child relation with an extension deployment descriptor entry only; in other words, no corresponding get child relation method is needed in the SBB abstract class. As such, these child relations are termed "declarative" child relations, to differentiate them from the standard child relations defined by the SLEE specification. Declarative child relations may be added to or removed from an SBB without the need to recompile any code.

Declarative child relations are declared in the oc-sbb-jar.xml extension deployment descriptor using the <child-relations> element. The child-relations element contains a child-relation element that defines each declarative child relation. A child-relation element contains the following sub-elements:

Sub-element What it does 
description

Provides information (optional).

 
child-relation-name

Defines the name of the declarative child relation. The SBB uses this name with the Child Relation Facility to access the child relation. This name must be unique within the scope of the SBB’s declarative child relations.

 
sbb-alias-ref

References an SBB by its sbb-alias that is specified within the corresponding sbb element in the standard sbb-jar.xml deployment descriptor. This element defines the type of the child SBB.

 
default-priority

Specifies the default event delivery priority of the child SBB relative to its sibling SBBs.

Child Relation Facility

The Child Relation Facility is a Rhino extension that is used by SBBs to gain access to their declarative child relations. The Child Relation Facility bypasses the need for the SBB developer to declare a get child relation method in the SBB abstract class for each child SBB that the SBB desires.

ChildRelationFacility interface

SBB objects access the Child Relation Facility through a ChildRelationFacility object that implements the ChildRelationFacility interface. A ChildRelationFacility object can be obtained from the SBB’s RhinoSbbContext object (an extension of the standard SbbContext object).

The ChildRelationFacility interface is as follows:

package com.opencloud.rhino.facilities.childrelations;

import java.util.Collection;
import javax.slee.ChildRelation;
import javax.slee.SbbLocalObject;
import javax.slee.TransactionRequiredLocalException;
import javax.slee.facilities.FacilityException;
import com.opencloud.rhino.slee.RhinoSbbContext;
import com.opencloud.rhino.slee.RhinoSbbLocalHome;

public interface ChildRelationFacility {
    public Collection<String> getChildRelationNames()
        throws FacilityException;

    public ChildRelation getChildRelation(String name)
        throws NullPointerException, TransactionRequiredLocalException, IllegalStateException,
               UnrecognizedChildRelationException, FacilityException;

    public Collection<SbbLocalObject> getChildSbbs()
        throws TransactionRequiredLocalException, IllegalStateException, FacilityException;

    public <T> Collection<T> getChildSbbs(Class<T> type)
        throws NullPointerException, TransactionRequiredLocalException,
               IllegalStateException, FacilityException;

    public RhinoSbbLocalHome getChildSbbLocalHome(String name)
        throws NullPointerException, UnrecognizedChildRelationException, FacilityException;
}
Note

  • All methods of the ChildRelationFacility interface, except for the getChildRelationNames method and the getChildSbbLocalHome method, are required transactional methods. The getChildRelationNames method and the getChildSbbLocalHome method are non-transactional.

  • The SLEE provides a concrete class implementing the ChildRelationFacility interface.

  • The methods of this interface throw the javax.slee.facilities.FacilityException if the requested operation cannot be completed because of a system-level failure.

getChildRelationNames method

The getChildRelationNames method returns the set of declarative child relation names declared by the SBB. Each name contained by this set corresponds with a name contained by a <child-relation-name> element in the oc-sbb-jar.xml extension deployment descriptor.

getChildRelation method

The getChildRelation method returns a standard ChildRelation object for the named declarative child relation. The specified name argument must be one of the names contained by the <child-relation-name> elements in the oc-sbb-jar.xml extension deployment descriptor; that is, it must be one of the names contained in the set of names returned by the getChildRelationNames method.

This method performs the same function as the get child relation methods declared in the SBB abstract class for standard JAIN SLEE child relation declarations. A ChildRelation object returned from this method can be used in exactly the same way as a ChildRelation object returned by a get child relation method.

This method throws a NullPointerException if the name argument is null. If the name argument does not correspond with a declarative child relation, then this method throws an UnrecognizedChildRelationException. If this method is invoked without a valid transaction context, then the method throws a TransactionRequiredLocalException. If the method is invoked by an SBB object that is not assigned to an SBB entity, then the method throws an IllegalStateException.

getChildSbbs methods

The getChildSbbs methods each return a collection of child SBB local interface objects. The no-argument variant returns a collection of all child SBBs. The one-argument variant returns a collection of all child SBBs where the child SBB’s local interface is assignable to the specified Class argument. Both these methods will consider all SBB child relations; that is, child relations declared both in the standard JAIN SLEE manner and declarative child relations.

If either of these methods are invoked without a valid transaction context then a TransactionRequiredLocalException is thrown. If invoked by an SBB object that is not assigned to an SBB entity, then an IllegalStateException is thrown. If the one-argument method variant is invoked with a null argument, then the method throws a NullPointerException.

getChildSbbLocalHome method

The getChildSbbLocalHome method returns an object implementing the local home interface of the child SBB of the named declarative child relation. For more information on SBB local home interfaces, please see Miscellaneous SLEE Application API Enhancements.

This method throws a NullPointerException if the name argument is null. If the name argument does not correspond with a declarative child relation, then this method throws an UnrecognizedChildRelationException.

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