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/*
* Copyright (c) OSGi Alliance (2002, 2013). All Rights Reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.osgi.service.wireadmin;
import java.util.Dictionary;
/**
* A connection between a Producer service and a Consumer service.
*
*
* A {@code Wire} object connects a Producer service to a Consumer service. Both
* the Producer and Consumer services are identified by their unique
* {@code service.pid} values. The Producer and Consumer services may
* communicate with each other via {@code Wire} objects that connect them. The
* Producer service may send updated values to the Consumer service by calling
* the {@link #update(Object)} method. The Consumer service may request an
* updated value from the Producer service by calling the {@link #poll()}
* method.
*
*
* A Producer service and a Consumer service may be connected through multiple
* {@code Wire} objects.
*
*
* Security Considerations. {@code Wire} objects are available to Producer and
* Consumer services connected to a given {@code Wire} object and to bundles
* which can access the {@code WireAdmin} service. A bundle must have
* {@code ServicePermission[WireAdmin,GET]} to get the {@code WireAdmin} service
* to access all {@code Wire} objects. A bundle registering a Producer service
* or a Consumer service must have the appropriate
* {@code ServicePermission[Consumer|Producer,REGISTER]} to register the service
* and will be passed {@code Wire} objects when the service object's
* {@code consumersConnected} or {@code producersConnected} method is called.
*
*
* Scope. Each Wire object can have a scope set with the {@code setScope}
* method. This method should be called by a Consumer service when it assumes a
* Producer service that is composite (supports multiple information items). The
* names in the scope must be verified by the {@code Wire} object before it is
* used in communication. The semantics of the names depend on the Producer
* service and must not be interpreted by the Wire Admin service.
*
* @noimplement
* @author $Id: de75c27d506f78112bce8a5289137ba5c0874344 $
*/
public interface Wire {
/**
* Return the state of this {@code Wire} object.
*
*
* A connected {@code Wire} must always be disconnected before becoming
* invalid.
*
* @return {@code false} if this {@code Wire} object is invalid because it
* has been deleted via {@link WireAdmin#deleteWire(Wire)};
* {@code true} otherwise.
*/
public boolean isValid();
/**
* Return the connection state of this {@code Wire} object.
*
*
* A {@code Wire} is connected after the Wire Admin service receives
* notification that the Producer service and the Consumer service for this
* {@code Wire} object are both registered. This method will return
* {@code true} prior to notifying the Producer and Consumer services via
* calls to their respective {@code consumersConnected} and
* {@code producersConnected} methods.
*
* A {@code WireAdminEvent} of type {@link WireAdminEvent#WIRE_CONNECTED}
* must be broadcast by the Wire Admin service when the {@code Wire} becomes
* connected.
*
*
* A {@code Wire} object is disconnected when either the Consumer or
* Producer service is unregistered or the {@code Wire} object is deleted.
*
* A {@code WireAdminEvent} of type {@link WireAdminEvent#WIRE_DISCONNECTED}
* must be broadcast by the Wire Admin service when the {@code Wire} becomes
* disconnected.
*
* @return {@code true} if both the Producer and Consumer for this
* {@code Wire} object are connected to the {@code Wire} object;
* {@code false} otherwise.
*/
public boolean isConnected();
/**
* Return the list of data types understood by the Consumer service
* connected to this {@code Wire} object. Note that subclasses of the
* classes in this list are acceptable data types as well.
*
*
* The list is the value of the
* {@link WireConstants#WIREADMIN_CONSUMER_FLAVORS} service property of the
* Consumer service object connected to this object. If no such property was
* registered or the type of the property value is not {@code Class[]}, this
* method must return {@code null}.
*
* @return An array containing the list of classes understood by the
* Consumer service or {@code null} if the {@code Wire} is not
* connected, or the consumer did not register a
* {@link WireConstants#WIREADMIN_CONSUMER_FLAVORS} property or the
* value of the property is not of type {@code Class[]}.
*/
public Class[] getFlavors();
/**
* Update the value.
*
*
* This methods is called by the Producer service to notify the Consumer
* service connected to this {@code Wire} object of an updated value.
*
* If the properties of this {@code Wire} object contain a
* {@link WireConstants#WIREADMIN_FILTER} property, then filtering is
* performed. If the Producer service connected to this {@code Wire} object
* was registered with the service property
* {@link WireConstants#WIREADMIN_PRODUCER_FILTERS}, the Producer service
* will perform the filtering according to the rules specified for the
* filter. Otherwise, this {@code Wire} object will perform the filtering of
* the value.
*
* If no filtering is done, or the filter indicates the updated value should
* be delivered to the Consumer service, then this {@code Wire} object must
* call the {@link Consumer#updated(Wire, Object)} method with the updated
* value. If this {@code Wire} object is not connected, then the Consumer
* service must not be called and the value is ignored.
*
* If the value is an {@code Envelope} object, and the scope name is not
* permitted, then the {@code Wire} object must ignore this call and not
* transfer the object to the Consumer service.
*
*
* A {@code WireAdminEvent} of type {@link WireAdminEvent#WIRE_TRACE} must
* be broadcast by the Wire Admin service after the Consumer service has
* been successfully called.
*
* @param value The updated value. The value should be an instance of one of
* the types returned by {@link #getFlavors()}.
* @see WireConstants#WIREADMIN_FILTER
*/
public void update(Object value);
/**
* Poll for an updated value.
*
*
* This methods is normally called by the Consumer service to request an
* updated value from the Producer service connected to this {@code Wire}
* object. This {@code Wire} object will call the
* {@link Producer#polled(Wire)} method to obtain an updated value. If this
* {@code Wire} object is not connected, then the Producer service must not
* be called.
*
*
* If this {@code Wire} object has a scope, then this method must return an
* array of {@code Envelope} objects. The objects returned must match the
* scope of this object. The {@code Wire} object must remove all
* {@code Envelope} objects with a scope name that is not in the
* {@code Wire} object's scope. Thus, the list of objects returned must only
* contain {@code Envelope} objects with a permitted scope name. If the
* array becomes empty, {@code null} must be returned.
*
*
* A {@code WireAdminEvent} of type {@link WireAdminEvent#WIRE_TRACE} must
* be broadcast by the Wire Admin service after the Producer service has
* been successfully called.
*
* @return A value whose type should be one of the types returned by
* {@link #getFlavors()},{@code Envelope[]}, or {@code null} if the
* {@code Wire} object is not connected, the Producer service threw
* an exception, or the Producer service returned a value which is
* not an instance of one of the types returned by
* {@link #getFlavors()}.
*/
public Object poll();
/**
* Return the last value sent through this {@code Wire} object.
*
*
* The returned value is the most recent, valid value passed to the
* {@link #update(Object)} method or returned by the {@link #poll()} method
* of this object. If filtering is performed by this {@code Wire} object,
* this methods returns the last value provided by the Producer service.
* This value may be an {@code Envelope[]} when the Producer service uses
* scoping. If the return value is an Envelope object (or array), it must be
* verified that the Consumer service has the proper WirePermission to see
* it.
*
* @return The last value passed though this {@code Wire} object or
* {@code null} if no valid values have been passed or the Consumer
* service has no permission.
*/
public Object getLastValue();
/**
* Return the wire properties for this {@code Wire} object.
*
* @return The properties for this {@code Wire} object. The returned
* {@code Dictionary} must be read only.
*/
public Dictionary getProperties();
/**
* Return the calculated scope of this {@code Wire} object.
*
* The purpose of the {@code Wire} object's scope is to allow a Producer
* and/or Consumer service to produce/consume different types over a single
* {@code Wire} object (this was deemed necessary for efficiency reasons).
* Both the Consumer service and the Producer service must set an array of
* scope names (their scope) with the service registration property
* {@code WIREADMIN_PRODUCER_SCOPE}, or {@code WIREADMIN_CONSUMER_SCOPE}
* when they can produce multiple types. If a Producer service can produce
* different types, it should set this property to the array of scope names
* it can produce, the Consumer service must set the array of scope names it
* can consume. The scope of a {@code Wire} object is defined as the
* intersection of permitted scope names of the Producer service and
* Consumer service.
*
* If neither the Consumer, or the Producer service registers scope names
* with its service registration, then the {@code Wire} object's scope must
* be {@code null}.
*
* The {@code Wire} object's scope must not change when a Producer or
* Consumer services modifies its scope.
*
* A scope name is permitted for a Producer service when the registering
* bundle has {@code WirePermission[name,PRODUCE]}, and for a Consumer
* service when the registering bundle has
* {@code WirePermission[name,CONSUME]}.
*
* If either Consumer service or Producer service has not set a
* {@code WIREADMIN_*_SCOPE} property, then the returned value must be
* {@code null}.
*
* If the scope is set, the {@code Wire} object must enforce the scope names
* when {@code Envelope} objects are used as a parameter to update or
* returned from the {@code poll} method. The {@code Wire} object must then
* remove all {@code Envelope} objects with a scope name that is not
* permitted.
*
* @return A list of permitted scope names or null if the Produce or
* Consumer service has set no scope names.
*/
public String[] getScope();
/**
* Return true if the given name is in this {@code Wire} object's scope.
*
* @param name The scope name
* @return true if the name is listed in the permitted scope names
*/
public boolean hasScope(String name);
}