/*
* Licensed to the Apache Software Foundation (ASF) under one or more contributor license
* agreements. See the NOTICE file distributed with this work for additional information regarding
* copyright ownership. The ASF licenses this file to You 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.apache.geode.cache.query;
import org.apache.geode.cache.CacheCallback;
/**
* Application plug-in interface for handling continuous query events after they occur. The listener
* has two methods, one that is called when there is an event satisfied by the CQ and the other
* called when there is an error during CQ processing.
*
* @since GemFire 5.5
*/
public interface CqListener extends CacheCallback {
/**
* This method is invoked when an event is occurred on the region that satisfied the query
* condition of this CQ. This event does not contain an error. If CQ is executed using
* ExecuteWithInitialResults the returned result may already include the changes with respect to
* this event. This could arise when updates are happening on the region while CQ registration is
* in progress. The CQ does not block any region operation as it could affect the performance of
* region operation. Its up to the application to synchronize between the region operation and CQ
* registration to avoid duplicate event being delivered.
*
* @see org.apache.geode.cache.query.CqQuery#executeWithInitialResults
*/
public void onEvent(CqEvent aCqEvent);
/**
* This method is invoked when there is an error during CQ processing. The error can appear while
* applying query condition on the event. e.g if the event doesn't has attributes as specified in
* the CQ query. This event does contain an error. The newValue may or may not be available, and
* will be null if not available.
*/
public void onError(CqEvent aCqEvent);
}