001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache license, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the license for the specific language governing permissions and
015 * limitations under the license.
016 */
017package org.apache.logging.log4j.util;
018
019/**
020 * Log4j API Constants.
021 *
022 * @since 2.6.2
023 */
024public final class Constants {
025    /**
026     * {@code true} if we think we are running in a web container, based on the boolean value of system property
027     * "log4j2.is.webapp", or (if this system property is not set) whether the  {@code javax.servlet.Servlet} class
028     * is present in the classpath.
029     */
030    public static final boolean IS_WEB_APP = PropertiesUtil.getProperties().getBooleanProperty(
031            "log4j2.is.webapp", isClassAvailable("javax.servlet.Servlet")
032                    || isClassAvailable("jakarta.servlet.Servlet"));
033
034    /**
035     * Kill switch for object pooling in ThreadLocals that enables much of the LOG4J2-1270 no-GC behaviour.
036     * <p>
037     * {@code True} for non-{@link #IS_WEB_APP web apps}, disable by setting system property
038     * "log4j2.enable.threadlocals" to "false".
039     * </p>
040     */
041    public static final boolean ENABLE_THREADLOCALS = !IS_WEB_APP && PropertiesUtil.getProperties().getBooleanProperty(
042            "log4j2.enable.threadlocals", true);
043
044    public static final int JAVA_MAJOR_VERSION = getMajorVersion();
045
046    /**
047     * Maximum size of the StringBuilders used in RingBuffer LogEvents to store the contents of reusable Messages.
048     * After a large message has been delivered to the appenders, the StringBuilder is trimmed to this size.
049     * <p>
050     * The default value is {@value}, which allows the StringBuilder to resize three times from its initial size.
051     * Users can override with system property "log4j.maxReusableMsgSize".
052     * </p>
053     * @since 2.9
054     */
055    public static final int MAX_REUSABLE_MESSAGE_SIZE = size("log4j.maxReusableMsgSize", (128 * 2 + 2) * 2 + 2);
056
057    /**
058     * Name of the system property that will turn on TRACE level internal log4j2 status logging.
059     * <p>
060     * If system property {@value} is either defined empty or its value equals to {@code true} (ignoring case), all internal log4j2 logging will be
061     * printed to the console. The presence of this system property overrides any value set in the configuration's
062     * {@code <Configuration status="<level>" ...>} status attribute, as well as any value set for
063     * system property {@code org.apache.logging.log4j.simplelog.StatusLogger.level}.
064     * </p>
065     */
066    public static final String LOG4J2_DEBUG = "log4j2.debug";
067
068    private static int size(final String property, final int defaultValue) {
069        return PropertiesUtil.getProperties().getIntegerProperty(property, defaultValue);
070    }
071
072    /**
073     * Determines if a named Class can be loaded or not.
074     *
075     * @param className The class name.
076     * @return {@code true} if the class could be found or {@code false} otherwise.
077     */
078    private static boolean isClassAvailable(final String className) {
079        try {
080            return LoaderUtil.loadClass(className) != null;
081        } catch (final Throwable e) {
082            return false;
083        }
084    }
085
086    /**
087     * The empty array.
088     */
089    public static final Object[] EMPTY_OBJECT_ARRAY = {};
090
091    /**
092     * The empty array.
093     */
094    public static final byte[] EMPTY_BYTE_ARRAY = {};
095
096    /**
097     * Prevent class instantiation.
098     */
099    private Constants() {
100    }
101
102    private static int getMajorVersion() {
103        return getMajorVersion(System.getProperty("java.version"));
104    }
105
106    static int getMajorVersion(final String version) {
107        final String[] parts = version.split("-|\\.");
108        boolean isJEP223;
109        try {
110            final int token = Integer.parseInt(parts[0]);
111            isJEP223 = token != 1;
112            if (isJEP223) {
113                return token;
114            }
115            return Integer.parseInt(parts[1]);
116        } catch (final Exception ex) {
117            return 0;
118        }
119    }
120}