/*
* 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.internal.cache.vmotion;
import org.apache.geode.cache.query.internal.Support;
/**
* This class is intended to hold a single 'observer' which will receive callbacks. There can be
* only one such observer at a time. If no observer is needed, this member variable should point to
* an object with 'do-nothing' methods, such as vMotionObserverAdapter.
*/
public class VMotionObserverHolder {
/**
* The default 'do-nothing' vMotion observer *
*/
public static final VMotionObserver NO_OBSERVER = new VMotionObserverAdapter();
/**
* The current observer which will be notified of all query events.
*/
private static VMotionObserver _instance = NO_OBSERVER;
/**
* Set the given observer to be notified of events. Returns the current observer.
*/
public static final VMotionObserver setInstance(VMotionObserver observer) {
Support.assertArg(observer != null, "setInstance expects a non-null argument!");
VMotionObserver oldObserver = _instance;
_instance = observer;
return oldObserver;
}
/** Return the current VMotionObserver instance */
public static final VMotionObserver getInstance() {
return _instance;
}
}