1 /* 2 * Copyright 2010 The Apache Software Foundation 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 package org.apache.hadoop.hbase.util; 21 22 /** 23 * Manages a singleton instance of the environment edge. This class shall 24 * implement static versions of the interface {@link EnvironmentEdge}, then 25 * defer to the delegate on invocation. 26 */ 27 public class EnvironmentEdgeManager { 28 private static volatile EnvironmentEdge delegate = new DefaultEnvironmentEdge(); 29 30 private EnvironmentEdgeManager() { 31 32 } 33 34 /** 35 * Retrieves the singleton instance of the {@link EnvironmentEdge} that is 36 * being managed. 37 * 38 * @return the edge. 39 */ 40 public static EnvironmentEdge getDelegate() { 41 return delegate; 42 } 43 44 /** 45 * Resets the managed instance to the default instance: {@link 46 * DefaultEnvironmentEdge}. 47 */ 48 static void reset() { 49 injectEdge(new DefaultEnvironmentEdge()); 50 } 51 52 /** 53 * Injects the given edge such that it becomes the managed entity. If null is 54 * passed to this method, the default type is assigned to the delegate. 55 * 56 * @param edge the new edge. 57 */ 58 static void injectEdge(EnvironmentEdge edge) { 59 if (edge == null) { 60 reset(); 61 } else { 62 delegate = edge; 63 } 64 } 65 66 /** 67 * Defers to the delegate and calls the 68 * {@link EnvironmentEdge#currentTimeMillis()} method. 69 * 70 * @return current time in millis according to the delegate. 71 */ 72 public static long currentTimeMillis() { 73 return getDelegate().currentTimeMillis(); 74 } 75 }