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/*-
* ============LICENSE_START=======================================================
* ONAP
* ================================================================================
* Copyright (C) 2020 AT&T Intellectual Property. 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.
* ============LICENSE_END=========================================================
*/
package org.onap.policy.controlloop.actorserviceprovider.topic;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.onap.policy.common.endpoints.event.comm.Topic.CommInfrastructure;
import org.onap.policy.common.endpoints.event.comm.TopicListener;
import org.onap.policy.common.utils.coder.CoderException;
import org.onap.policy.common.utils.coder.StandardCoder;
import org.onap.policy.common.utils.coder.StandardCoderObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A topic listener. When a message arrives on a topic, it is forwarded to listeners based
* on the content of fields found within the message. However, depending on the message
* type, the relevant fields might be found in different places within the message's
* object hierarchy. For each different list of keys, this class maintains a
* {@link Forwarder}, which is used to forward the message to all relevant listeners.
* <p/>
* Once a selector has been added, it is not removed until {@link #shutdown()} is invoked.
* As selectors are typically only added by Operators, and not by individual Operations,
* this should not pose a problem.
*/
public class TopicListenerImpl implements TopicListener {
private static final Logger logger = LoggerFactory.getLogger(TopicListenerImpl.class);
private static StandardCoder coder = new StandardCoder();
/**
* Maps selector to a forwarder.
*/
private final Map<List<SelectorKey>, Forwarder> selector2forwarder = new ConcurrentHashMap<>();
/**
* Removes all forwarders.
*/
public void shutdown() {
selector2forwarder.clear();
}
/**
* Adds a forwarder, if it doesn't already exist.
*
* @param keys the selector keys
* @return the forwarder associated with the given selector keys
*/
public Forwarder addForwarder(SelectorKey... keys) {
return addForwarder(Arrays.asList(keys));
}
/**
* Adds a forwarder, if it doesn't already exist.
*
* @param keys the selector keys
* @return the forwarder associated with the given selector keys
*/
public Forwarder addForwarder(List<SelectorKey> keys) {
return selector2forwarder.computeIfAbsent(keys, key -> new Forwarder(keys));
}
/**
* Decodes the message and then forwards it to each forwarder for processing.
*/
@Override
public void onTopicEvent(CommInfrastructure infra, String topic, String message) {
StandardCoderObject object;
try {
object = coder.decode(message, StandardCoderObject.class);
} catch (CoderException e) {
logger.warn("cannot decode message", e);
return;
}
/*
* We don't know which selector is appropriate for the message, so we just let
* them all take a crack at it.
*/
for (Forwarder forwarder : selector2forwarder.values()) {
forwarder.onMessage(message, object);
}
}
}
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