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.util;
18
19 /**
20 * Log4j API Constants.
21 *
22 * @since 2.6.2
23 */
24 public final class Constants {
25 /**
26 * {@code true} if we think we are running in a web container, based on the boolean value of system property
27 * "log4j2.is.webapp", or (if this system property is not set) whether the {@code javax.servlet.Servlet} class
28 * is present in the classpath.
29 */
30 public static final boolean IS_WEB_APP = PropertiesUtil.getProperties().getBooleanProperty(
31 "log4j2.is.webapp", isClassAvailable("javax.servlet.Servlet"));
32
33 /**
34 * Kill switch for object pooling in ThreadLocals that enables much of the LOG4J2-1270 no-GC behaviour.
35 * <p>
36 * {@code True} for non-{@link #IS_WEB_APP web apps}, disable by setting system property
37 * "log4j2.enable.threadlocals" to "false".
38 * </p>
39 */
40 public static final boolean ENABLE_THREADLOCALS = !IS_WEB_APP && PropertiesUtil.getProperties().getBooleanProperty(
41 "log4j2.enable.threadlocals", true);
42
43 /**
44 * Determines if a named Class can be loaded or not.
45 *
46 * @param className The class name.
47 * @return {@code true} if the class could be found or {@code false} otherwise.
48 */
49 private static boolean isClassAvailable(final String className) {
50 try {
51 return LoaderUtil.loadClass(className) != null;
52 } catch (final Throwable e) {
53 return false;
54 }
55 }
56
57 /**
58 * Prevent class instantiation.
59 */
60 private Constants() {
61 }
62 }