org.jacorb.notification

Class FilterImpl

Implemented Interfaces:
Configurable, Disposable, FilterOperations, InvokeHandler, ManageableServant

public class FilterImpl
extends FilterPOA
implements Disposable, ManageableServant, Configurable

The Filter interface defines the behaviors supported by objects which encapsulate constraints used by the proxy objects associated with an event channel in order to determine which events they receive will be forwarded, and which will be discarded. Each object supporting the Filter interface can encapsulate a sequence of any number of constraints. Each event received by a proxy object which has one or more objects supporting the Filter interface associated with it must satisfy at least one of the constraints associated with one of its associated Filter objects in order to be forwarded (either to another proxy object or to the consumer, depending on the type of proxy the filter is associated with), otherwise it will be discarded.
Each constraint encapsulated by a filter object is a structure comprised of two main components. The first component is a sequence of data structures, each of which indicates an event type comprised of a domain and a type name. The second component is a boolean expression over the properties of an event, expressed in some constraint grammar (more on this below). For a given constraint, the sequence of event type structures in the first component nominates a set of event types to which the constraint expression in the second component applies. Each element of the sequence can contain strings which will be matched for equality against the domain_name and type_name fields of each event being evaluated by the filter object, or it could contain strings with wildcard symbols (*), indicating a pattern match should be performed against the type contained in each event, rather than a comparison for equality when determining if the boolean expression should be applied to the event, or the event should simply be discarded without even attempting to apply the boolean expression. Note that an empty sequence included as the first component of a constraint implies that the associated expression applies to all types of events, as does a sequence comprised of a single element whose domain and type name are both set to either the empty string or else the wildcard symbol alone contained in quotes.
The constraint expressions associated with a particular object supporting the Filter interface are expressed as strings which obey the syntax of a particular constraint grammar (i.e., a BNF). Every conformant implementation of this service must support constraint expressions expressed in the default constraint grammar described in Section 2.4, "The Default Filter Constraint Language," on page 2-23. In addition, implementations may support other constraint grammars, and/or users of this service may implement their own filter objects which allow constraints to be expressed in terms of an alternative constraint grammar. As long as such user-defined filter objects support the Filter interface, they can be attached to Proxy or Admin objects in the same fashion as the default Filter objects supported by the implementation of the service are, and the channel should be able to use them to filter events in the same fashion.
The Filter interface supports the operations required to manage the constraints associated with an object instance which supports the interface, along with a readonly attribute which identifies the particular constraint grammar in which the constraints encapsulated by this object have meaning. In addition, the Filter interface supports three variants of the match operation which can be invoked by an associated proxy object upon receipt of an event (the specific variant selected depends upon whether the event is received in the form of an Any, a Structured Event, or a Typed Event), to determine if the event should be forwarded or discarded, based on whether or not the event satisfies at least one criteria encapsulated by the filter object. The Filter interface also supports operations which enable a client to associate with the target filter object any number of "callbacks" which are notified each time there is a change to the list of event types which the constraints encapsulated by the filter object could potentially cause proxies to which the filter is attached to receive. Operations are also defined to support administration of this callback list by unique identifier.

Version:
$Id: FilterImpl.java,v 1.22 2004/05/06 12:39:59 nicolas Exp $

Authors:
Alphonse Bendt
John Farrell

Field Summary

static int
CONSTRAINTS_EMPTY
static int
NO_CONSTRAINTS_MATCH
protected Map
callbacks_
contains a number of callbacks, which are notified each time there is a change to the list of constraints. (does not work yet)
protected ReadWriteLock
constraintsLock_
protected Map
constraints_
contains the associated constraints.
protected DynAnyFactory
dynAnyFactory_
protected DynamicEvaluator
dynamicEvaluator_
protected MessageFactory
messageFactory_
protected WildcardMap
wildcardMap_

Constructor Summary

FilterImpl(ApplicationContext applicationContext, String constraintGrammar)

Method Summary

POA
_default_POA()
Object
activate()
ConstraintInfo[]
add_constraints(ConstraintExp constraintExp)
The add_constraints operation is invoked by a client in order to associate one or more new constraints with the target filter object.
int
attach_callback(NotifySubscribe notifySubscribe)
void
configure(Configuration conf)
String
constraint_grammar()
The constraint_grammar attribute is a readonly attribute which identifies the particular grammar within which the constraint expressions encapsulated by the target filter object have meaning.
void
deactivate()
void
destroy()
void
detach_callback(int id)
void
dispose()
protected int
getConstraintId()
Iterator
getIterator(Object key)
ConstraintInfo[]
get_all_constraints()
int[]
get_callbacks()
ConstraintInfo[]
get_constraints(int[] ids)
boolean
match(Any anyEvent)
protected int
match_internal(Any anyEvent)
match Any to associated constraints. return the id of the first matching filter or NO_CONSTRAINT.
boolean
match_structured(StructuredEvent structuredevent)
protected int
match_structured_internal(StructuredEvent structuredEvent)
match the StructuredEvent to the associated constraints. return the id of the first matching filter or NO_CONSTRAINT.
boolean
match_typed(Property properties)
void
modify_constraints(int[] deleteIds, ConstraintInfo constraintInfo)
void
preActivate()
void
remove_all_constraints()
void
setDisposeHook(Runnable disposeHook)
void
setORB(ORB orb)
void
setPOA(POA poa)

Methods inherited from class org.omg.CosNotifyFilter.FilterPOA

_all_interfaces, _invoke, _this, _this

Methods inherited from class org.omg.PortableServer.Servant

_all_interfaces, _default_POA, _get_delegate, _get_interface, _get_interface_def, _is_a, _non_existent, _object_id, _orb, _poa, _set_delegate, _this_object, _this_object

Field Details

CONSTRAINTS_EMPTY

public static final int CONSTRAINTS_EMPTY

Field Value:
-1


NO_CONSTRAINTS_MATCH

public static final int NO_CONSTRAINTS_MATCH

Field Value:
-2


callbacks_

protected Map callbacks_
contains a number of callbacks, which are notified each time there is a change to the list of constraints. (does not work yet)


constraintsLock_

protected ReadWriteLock constraintsLock_


constraints_

protected Map constraints_
contains the associated constraints.


dynAnyFactory_

protected DynAnyFactory dynAnyFactory_


dynamicEvaluator_

protected DynamicEvaluator dynamicEvaluator_


messageFactory_

protected MessageFactory messageFactory_


wildcardMap_

protected WildcardMap wildcardMap_

Constructor Details

FilterImpl

public FilterImpl(ApplicationContext applicationContext,
                  String constraintGrammar)

Method Details

_default_POA

public POA _default_POA()
Overrides:
_default_POA in interface Servant


activate

public Object activate()
Specified by:
activate in interface ManageableServant


add_constraints

public ConstraintInfo[] add_constraints(ConstraintExp constraintExp)
            throws InvalidConstraint
The add_constraints operation is invoked by a client in order to associate one or more new constraints with the target filter object. The operation accepts as input a sequence of constraint data structures, each element of which consists of a sequence of event type structures (described in Section 3.2.1, "The Filter Interface," on page 3-14) and a constraint expressed within the constraint grammar supported by the target object. Upon processing each constraint, the target object associates a numeric identifier with the constraint that is unique among all constraints it encapsulates. If any of the constraints in the input sequence is not a valid expression within the supported constraint grammar, the InvalidConstraint exception is raised. This exception contains as data the specific constraint expression that was determined to be invalid. Upon successful processing of all input constraint expressions, the add_constraints operation returns a sequence in which each element will be a structure including one of the input constraint expressions, along with the unique identifier assigned to it by the target filter object.
Note that the semantics of the add_constraints operation are such that its sideeffects are performed atomically upon the target filter object. Once add_constraints is invoked by a client, the target filter object is temporarily disabled from usage by any proxy object it may be associated with. The operation is then carried out, either successfully adding all of the input constraints to the target object or none of them (in the case one of the input expressions was invalid). Upon completion of the operation, the target filter object is effectively re-enabled and can once again be used by associated filter objects in order to make event forwarding decisions.


attach_callback

public int attach_callback(NotifySubscribe notifySubscribe)
Specified by:
attach_callback in interface FilterOperations


configure

public void configure(Configuration conf)


constraint_grammar

public String constraint_grammar()
The constraint_grammar attribute is a readonly attribute which identifies the particular grammar within which the constraint expressions encapsulated by the target filter object have meaning.
Specified by:
constraint_grammar in interface FilterOperations


deactivate

public void deactivate()
Specified by:
deactivate in interface ManageableServant


destroy

public void destroy()
Specified by:
destroy in interface FilterOperations


detach_callback

public void detach_callback(int id)
Specified by:
detach_callback in interface FilterOperations


dispose

public void dispose()
Specified by:
dispose in interface Disposable


getConstraintId

protected int getConstraintId()


getIterator

public Iterator getIterator(Object key)


get_all_constraints

public ConstraintInfo[] get_all_constraints()
Specified by:
get_all_constraints in interface FilterOperations


get_callbacks

public int[] get_callbacks()
Specified by:
get_callbacks in interface FilterOperations


get_constraints

public ConstraintInfo[] get_constraints(int[] ids)
            throws ConstraintNotFound
Specified by:
get_constraints in interface FilterOperations


match

public boolean match(Any anyEvent)
            throws UnsupportedFilterableData
Specified by:
match in interface FilterOperations


match_internal

protected int match_internal(Any anyEvent)
            throws UnsupportedFilterableData
match Any to associated constraints. return the id of the first matching filter or NO_CONSTRAINT.


match_structured

public boolean match_structured(StructuredEvent structuredevent)
            throws UnsupportedFilterableData
Specified by:
match_structured in interface FilterOperations


match_structured_internal

protected int match_structured_internal(StructuredEvent structuredEvent)
            throws UnsupportedFilterableData
match the StructuredEvent to the associated constraints. return the id of the first matching filter or NO_CONSTRAINT.


match_typed

public boolean match_typed(Property properties)
            throws UnsupportedFilterableData


modify_constraints

public void modify_constraints(int[] deleteIds,
                               ConstraintInfo constraintInfo)
            throws ConstraintNotFound,
                   InvalidConstraint


preActivate

public void preActivate()
Specified by:
preActivate in interface ManageableServant


remove_all_constraints

public void remove_all_constraints()
Specified by:
remove_all_constraints in interface FilterOperations


setDisposeHook

public void setDisposeHook(Runnable disposeHook)


setORB

public void setORB(ORB orb)
Specified by:
setORB in interface ManageableServant


setPOA

public void setPOA(POA poa)
Specified by:
setPOA in interface ManageableServant