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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;
/**
* Data Consumer, a service that can receive udpated values from
* {@link Producer} services.
*
*
* Service objects registered under the {@code Consumer} interface are expected
* to consume values from a Producer service via a {@code Wire} object. A
* Consumer service may poll the Producer service by calling the
* {@link Wire#poll()} method. The Consumer service will also receive an updated
* value when called at it's {@link #updated(Wire, Object)} method. The Producer
* service should have coerced the value to be an instance of one of the types
* specified by the {@link Wire#getFlavors()} method, or one of their
* subclasses.
*
*
* Consumer service objects must register with a {@code service.pid} and a
* {@link WireConstants#WIREADMIN_CONSUMER_FLAVORS} property. It is recommended
* that Consumer service objects also register with a
* {@code service.description} property.
*
*
* If an {@code Exception} is thrown by any of the {@code Consumer} methods, a
* {@code WireAdminEvent} of type {@link WireAdminEvent#CONSUMER_EXCEPTION} is
* broadcast by the Wire Admin service.
*
*
* Security Considerations - Data consuming bundles will require
* {@code ServicePermission[Consumer,REGISTER]}. In general, only the Wire Admin
* service bundle should have this permission. Thus only the Wire Admin service
* may directly call a Consumer service. Care must be taken in the sharing of
* {@code Wire} objects with other bundles.
*
* Consumer services must be registered with their scope when they can receive
* different types of objects from the Producer service. The Consumer service
* should have {@code WirePermission} for each of these scope names.
*
* @author $Id: 3363ead47a7767d56aa9199473ef4c529e9672eb $
*/
public interface Consumer {
/**
* Update the value. This Consumer service is called by the {@code Wire}
* object with an updated value from the Producer service.
*
*
* Note: This method may be called by a {@code Wire} object prior to this
* object being notified that it is connected to that {@code Wire} object
* (via the {@link #producersConnected(Wire[])} method).
*
* When the Consumer service can receive {@code Envelope} objects, it must
* have registered all scope names together with the service object, and
* each of those names must be permitted by the bundle's
* {@code WirePermission}. If an {@code Envelope} object is delivered with
* the {@code updated} method, then the Consumer service should assume that
* the security check has been performed.
*
* @param wire The {@code Wire} object which is delivering the updated
* value.
* @param value The updated value. The value should be an instance of one of
* the types specified by the {@link Wire#getFlavors()} method.
*/
public void updated(Wire wire, Object value);
/**
* Update the list of {@code Wire} objects to which this Consumer service is
* connected.
*
*
* This method is called when the Consumer service is first registered and
* subsequently whenever a {@code Wire} associated with this Consumer
* service becomes connected, is modified or becomes disconnected.
*
*
* The Wire Admin service must call this method asynchronously. This implies
* that implementors of Consumer can be assured that the callback will not
* take place during registration when they execute the registration in a
* synchronized method.
*
* @param wires An array of the current and complete list of {@code Wire}
* objects to which this Consumer service is connected. May be
* {@code null} if the Consumer service is not currently connected to
* any {@code Wire} objects.
*/
public void producersConnected(Wire[] wires);
}