1 /*
2 *
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19 package org.apache.hadoop.hbase.util;
20
21 import org.apache.hadoop.hbase.classification.InterfaceAudience;
22
23 /**
24 * Manages a singleton instance of the environment edge. This class shall
25 * implement static versions of the interface {@link EnvironmentEdge}, then
26 * defer to the delegate on invocation.
27 */
28 @InterfaceAudience.Private
29 public class EnvironmentEdgeManager {
30 private static volatile EnvironmentEdge delegate = new DefaultEnvironmentEdge();
31
32 private EnvironmentEdgeManager() {
33
34 }
35
36 /**
37 * Retrieves the singleton instance of the {@link EnvironmentEdge} that is
38 * being managed.
39 *
40 * @return the edge.
41 */
42 public static EnvironmentEdge getDelegate() {
43 return delegate;
44 }
45
46 /**
47 * Resets the managed instance to the default instance: {@link
48 * DefaultEnvironmentEdge}.
49 */
50 public static void reset() {
51 injectEdge(new DefaultEnvironmentEdge());
52 }
53
54 /**
55 * Injects the given edge such that it becomes the managed entity. If null is
56 * passed to this method, the default type is assigned to the delegate.
57 *
58 * @param edge the new edge.
59 */
60 public static void injectEdge(EnvironmentEdge edge) {
61 if (edge == null) {
62 reset();
63 } else {
64 delegate = edge;
65 }
66 }
67
68 /**
69 * Defers to the delegate and calls the
70 * {@link EnvironmentEdge#currentTime()} method.
71 *
72 * @return current time in millis according to the delegate.
73 */
74 public static long currentTime() {
75 return getDelegate().currentTime();
76 }
77 }