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.classification.InterfaceAudience;
22 import org.apache.hadoop.classification.InterfaceStability;
23
24 /**
25 * Manages a singleton instance of the environment edge. This class shall
26 * implement static versions of the interface {@link EnvironmentEdge}, then
27 * defer to the delegate on invocation.
28 */
29 @InterfaceAudience.Public
30 @InterfaceStability.Evolving
31 public class EnvironmentEdgeManager {
32 private static volatile EnvironmentEdge delegate = new DefaultEnvironmentEdge();
33
34 private EnvironmentEdgeManager() {
35
36 }
37
38 /**
39 * Retrieves the singleton instance of the {@link EnvironmentEdge} that is
40 * being managed.
41 *
42 * @return the edge.
43 */
44 public static EnvironmentEdge getDelegate() {
45 return delegate;
46 }
47
48 /**
49 * Resets the managed instance to the default instance: {@link
50 * DefaultEnvironmentEdge}.
51 */
52 public static void reset() {
53 injectEdge(new DefaultEnvironmentEdge());
54 }
55
56 /**
57 * Injects the given edge such that it becomes the managed entity. If null is
58 * passed to this method, the default type is assigned to the delegate.
59 *
60 * @param edge the new edge.
61 */
62 public static void injectEdge(EnvironmentEdge edge) {
63 if (edge == null) {
64 reset();
65 } else {
66 delegate = edge;
67 }
68 }
69
70 /**
71 * Defers to the delegate and calls the
72 * {@link EnvironmentEdge#currentTimeMillis()} method.
73 *
74 * @return current time in millis according to the delegate.
75 */
76 public static long currentTimeMillis() {
77 return getDelegate().currentTimeMillis();
78 }
79 }