1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache license, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the license for the specific language governing permissions and
15 * limitations under the license.
16 */
17 package org.apache.logging.log4j.core.util;
18
19 import org.apache.logging.log4j.status.StatusLogger;
20 import org.apache.logging.log4j.util.PropertiesUtil;
21
22 /**
23 * Factory for {@code Clock} objects.
24 */
25 public final class ClockFactory {
26
27 /**
28 * Name of the system property that can be used to specify a {@code Clock}
29 * implementation class. The value of this property is {@value}.
30 */
31 public static final String PROPERTY_NAME = "log4j.Clock";
32 private static final StatusLogger LOGGER = StatusLogger.getLogger();
33
34 // private static final Clock clock = createClock();
35
36 private ClockFactory() {
37 }
38
39 /**
40 * Returns a {@code Clock} instance depending on the value of system
41 * property {@link #PROPERTY_NAME}.
42 * <p>
43 * If system property {@code log4j.Clock=CachedClock} is specified,
44 * this method returns an instance of {@link CachedClock}. If system
45 * property {@code log4j.Clock=CoarseCachedClock} is specified, this
46 * method returns an instance of {@link CoarseCachedClock}.
47 * </p>
48 * <p>
49 * If another value is specified, this value is taken as the fully qualified
50 * class name of a class that implements the {@code Clock} interface. An
51 * object of this class is instantiated and returned.
52 * </p>
53 * <p>
54 * If no value is specified, or if the specified value could not correctly
55 * be instantiated or did not implement the {@code Clock} interface, then an
56 * instance of {@link SystemClock} is returned.
57 * </p>
58 *
59 * @return a {@code Clock} instance
60 */
61 public static Clock getClock() {
62 return createClock();
63 }
64
65 private static Clock createClock() {
66 final String userRequest = PropertiesUtil.getProperties().getStringProperty(PROPERTY_NAME);
67 if (userRequest == null || "SystemClock".equals(userRequest)) {
68 LOGGER.debug("Using default SystemClock for timestamps");
69 return new SystemClock();
70 }
71 if (CachedClock.class.getName().equals(userRequest)
72 || "CachedClock".equals(userRequest)) {
73 LOGGER.debug("Using specified CachedClock for timestamps");
74 return CachedClock.instance();
75 }
76 if (CoarseCachedClock.class.getName().equals(userRequest)
77 || "CoarseCachedClock".equals(userRequest)) {
78 LOGGER.debug("Using specified CoarseCachedClock for timestamps");
79 return CoarseCachedClock.instance();
80 }
81 try {
82 final Clock result = Loader.newCheckedInstanceOf(userRequest, Clock.class);
83 LOGGER.debug("Using {} for timestamps", result.getClass().getName());
84 return result;
85 } catch (final Exception e) {
86 final String fmt = "Could not create {}: {}, using default SystemClock for timestamps";
87 LOGGER.error(fmt, userRequest, e);
88 return new SystemClock();
89 }
90 }
91 }