Portable Object Adaptor in Allegro CL

We make no attempt to explain POA here. We only mention aspects of our implementation that affect an application's use of ORBLink with POA.

User-visible changes:

• The _mark attribute of servant objects is no longer used to provide an object id. User-supplied object ids are mediated by the POA system.
• A reference unmartialed from an incoming request that refers to a servant in the processing ORBLink is no longer unmartialed as a servant object. It is unmartialed as a proxy, so operations on it will satisfy the POA rules.
• There is a new package containing the POA components, per the mapping rules:
  • package name: omg.org/PortableServer
  • package nicknames: PortableServer, poa, omg.poa, orblink.poa
• (op:resolve_initial_references corba:orb "RootPOA") returns the root POA. This POA can be used to register objects, but is not the default POA.
• (op:resolve_initial_references corba:orb "POACurrent") returns an instance of the poa:current class to use in context operations.
• There are three predefined POA's in ORBLink, sharing a single poamanager. See the poa:default-poa function for more information.

New conditions, as defined by POA spec.

• poa:poa-exception -- superclass of all the poa exceptions
• poa:forwardrequest
• poa:current/nocontext
• poa:poamanager/adapterinactive
• poa:adapteralreadyexists
• poa:adapternonexistent
• poa:invalidpolicy
• poa:noservant
• poa:objectalreadyactive
• poa:objectnotactive
• poa:servantalreadyactive
• poa:servantnotactive
• poa:wrongadapter
• poa:wrongpolicy

New classes

Policy classes:

• poa:threadpolicy
• poa:lifespanpolicy
• poa:iduniquenesspolicy
• poa:idassignmentpolicy
• poa:implicitactivationpolicy
• poa:servantretentionpolicy
• poa:requestprocessingpolicy

Other classes

• poa:poa
• poa:userid -- a mixin class. A method for poa:default-poa is specialized on this class returns a particular (predefined) poa that supports user-specified object id's. See the discussion of the default-poa function.
• poa:poamanager
• poa:adapteractivater -- to be subclassed to provide for method specialization
• poa:servantmanager -- superclass of poa:servantactivator and poa:servantlocator
• poa:servantactivator -- to be subclassed to provide for method specialization
• poa:servantlocator -- to be subclassed to provide for method specialization
• poa:current

New type names

• poa:threadpolicyvalue-type = (member :orb_ctrl_model :single_thread_model)
• poa:lifespanpolicyvalue-type = (member :transient :persistent)
• poa:iduniquenesspolicyvalue-type = (member :unique_id :multiple_id)
• poa:idassignmentpolicyvalue-type = (member :user_id :system_id)
• poa:implicitactivationpolicyvalue-type = (member :implicit_activation :no_implicit_activation)
• poa:servantretentionpolicyvalue-type = (member :retain :non_retain)
• poa:requestprocessingpolicyvalue-type = (member :use_active_object_map_only :use_default_servant :use_servant_manager)

New functions

• (poa:default-poa object)

  A generic function. A method specialized on corba:servant returns a particular :retain :system_id :transient :implicit_activation :use_active_object_map_only POA that approximates the semantics of pre-POA ORBLink.

  A second POA, with :no_implicit_activation and :user_id policies, is returned by a method specialized on poa:user-id. This allows an application to mix the poa:user-id class in to an implementation to get a default user_id POA for instances of that class.

  Applications can provide methods specialized on any implementation classes to use specific POAs.

• Predicates to test policy values
  • (poa:threadpolicyvalue-type-predicate x) == (typep x 'poa:threadpolicyvalue-type)
  • (poa:lifespanpolicyvalue-type-predicate x) == (typep x 'poa:lifespanpolicyvalue-type)
  • (poa:iduniquenesspolicyvalue-type-predicate x) == (typep x 'poa:iduniquenesspolicyvalue-type)
  • (poa:idassignmentpolicyvalue-type-predicate x) == (typep x 'poa:idassignmentpolicyvalue-type)
  • (poa:implicitactivationpolicyvalue-type-predicate x) == (typep x 'poa:implicitactivationpolicyvalue-type)
  • (poa:servantretentionpolicyvalue-type-predicate x) == (typep x 'poa:servantretentionpolicyvalue-type)
  • (poa:requestprocessingpolicyvalue-type-predicate x) == (typep x 'poa:requestprocessingpolicyvalue-type)
• Other functions
  • (poa:proxy-from-reference reference) -- returns a proxy object (of the correct type) to allow access to the object reference.
  • (poa:poa-has-policy poa keyword) -- returns true if and only if the keyword is a POA policy value and the POA has a policy with that value.
  • (poa:poa-policies &rest keys) -- useful for generating a sequence of policy objects with the specified values. Such a sequence is needed when creating POAs.