| /* |
| * 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. |
| */ |
| /* |
| * Created on Sep 12, 2005 |
| * |
| * |
| */ |
| package org.apache.geode.internal.cache; |
| |
| import org.apache.geode.annotations.Immutable; |
| import org.apache.geode.annotations.internal.MakeNotStatic; |
| |
| /** |
| * This class is intended to hold a single 'observer' which will receive callbacks from the |
| * Distributed/Local Region when events like clear take place. 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 CacheObserverAdapter. |
| * |
| * Code which wishes to observe events during Region clear should do so using the following |
| * technique: |
| * |
| * class MyCacheObserver extends CacheObserverAdapter { // ... override methods of interest ... } |
| * |
| * CacheObserver old = CacheObserverHolder.setInstance(new MyCacheObserver()); |
| * org.apache.geode.internal.cache.LocalRegion.ISSUE_CALLBACKS_TO_CACHE_OBSERVER=true; |
| * |
| * try { Call region methods here } finally { // reset to the original CacheObserver. |
| * CacheObserverHolder.setInstance(old); } |
| * |
| * The Region code will call methods on this static member using the following technique: |
| * |
| * CacheObserver observer = CacheObserverHolder.getInstance(); try { |
| * observer.startMethod(arguments); doSomething(); } finally { observer.stopMethod(arguments); } |
| * |
| */ |
| public class CacheObserverHolder { |
| |
| /** |
| * The default 'do-nothing' query observer * |
| */ |
| @Immutable |
| private static final CacheObserver NO_OBSERVER = new CacheObserverAdapter(); |
| /** |
| * The current observer which will be notified of all query events. |
| */ |
| @MakeNotStatic |
| private static CacheObserver _instance = NO_OBSERVER; |
| |
| /** |
| * Set the given observer to be notified of query events. Returns the current observer. |
| */ |
| public static CacheObserver setInstance(CacheObserver observer) { |
| if (observer == null) |
| observer = NO_OBSERVER; |
| CacheObserver oldObserver = _instance; |
| _instance = observer; |
| return oldObserver; |
| } |
| |
| /** Return the current QueryObserver instance */ |
| public static CacheObserver getInstance() { |
| return _instance; |
| } |
| } |