/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache license, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the license for the specific language governing permissions and
 * limitations under the license.
 */
package org.apache.logging.log4j.util;

Log4j API Constants.
Since:
2.6.2/**
 * Log4j API Constants.
 *
 * @since 2.6.2
 */
public final class Constants {
    
true if we think we are running in a web container, based on the boolean value of system property "log4j2.is.webapp", or (if this system property is not set) whether the javax.servlet.Servlet class is present in the classpath. /**
     * {@code true} if we think we are running in a web container, based on the boolean value of system property
     * "log4j2.is.webapp", or (if this system property is not set) whether the  {@code javax.servlet.Servlet} class
     * is present in the classpath.
     */
    public static final boolean IS_WEB_APP = PropertiesUtil.getProperties().getBooleanProperty(
            "log4j2.is.webapp", isClassAvailable("javax.servlet.Servlet"));

    
Kill switch for object pooling in ThreadLocals that enables much of the LOG4J2-1270 no-GC behaviour.
 True for non-web apps, disable by setting system property "log4j2.enable.threadlocals" to "false". 
/**
     * Kill switch for object pooling in ThreadLocals that enables much of the LOG4J2-1270 no-GC behaviour.
     * <p>
     * {@code True} for non-{@link #IS_WEB_APP web apps}, disable by setting system property
     * "log4j2.enable.threadlocals" to "false".
     * </p>
     */
    public static final boolean ENABLE_THREADLOCALS = !IS_WEB_APP && PropertiesUtil.getProperties().getBooleanProperty(
            "log4j2.enable.threadlocals", true);

    public static final int JAVA_MAJOR_VERSION = getMajorVersion();

    
Maximum size of the StringBuilders used in RingBuffer LogEvents to store the contents of reusable Messages.
After a large message has been delivered to the appenders, the StringBuilder is trimmed to this size.
 The default value is {@value}, which allows the StringBuilder to resize three times from its initial size. Users can override with system property "log4j.maxReusableMsgSize". 
Since:
2.9/**
     * Maximum size of the StringBuilders used in RingBuffer LogEvents to store the contents of reusable Messages.
     * After a large message has been delivered to the appenders, the StringBuilder is trimmed to this size.
     * <p>
     * The default value is {@value}, which allows the StringBuilder to resize three times from its initial size.
     * Users can override with system property "log4j.maxReusableMsgSize".
     * </p>
     * @since 2.9
     */
    public static final int MAX_REUSABLE_MESSAGE_SIZE = size("log4j.maxReusableMsgSize", (128 * 2 + 2) * 2 + 2);

    
Name of the system property that will turn on TRACE level internal log4j2 status logging.
 If system property "log4j2.debug" is defined, regardless of the property value, all internal log4j2 logging will be printed to the console. The presence of this system property overrides any value set in the configuration's <Configuration status="<level>" ...> status attribute, as well as any value set for system property org.apache.logging.log4j.simplelog.StatusLogger.level. 
/**
     * Name of the system property that will turn on TRACE level internal log4j2 status logging.
     * <p>
     * If system property {@value} is defined, regardless of the property value, all internal log4j2 logging will be
     * printed to the console. The presence of this system property overrides any value set in the configuration's
     * {@code <Configuration status="<level>" ...>} status attribute, as well as any value set for
     * system property {@code org.apache.logging.log4j.simplelog.StatusLogger.level}.
     * </p>
     */
    public static final String LOG4J2_DEBUG = "log4j2.debug";

    private static int size(final String property, final int defaultValue) {
        return PropertiesUtil.getProperties().getIntegerProperty(property, defaultValue);
    }

    
Determines if a named Class can be loaded or not.
Params:
className – The class name.
Returns:
true if the class could be found or false otherwise./**
     * Determines if a named Class can be loaded or not.
     *
     * @param className The class name.
     * @return {@code true} if the class could be found or {@code false} otherwise.
     */
    private static boolean isClassAvailable(final String className) {
        try {
            return LoaderUtil.loadClass(className) != null;
        } catch (final Throwable e) {
            return false;
        }
    }

    
Prevent class instantiation.
/**
     * Prevent class instantiation.
     */
    private Constants() {
    }

    private static int getMajorVersion() {
        return getMajorVersion(System.getProperty("java.version"));
    }

    static int getMajorVersion(final String version) {
        final String[] parts = version.split("-|\\.");
        boolean isJEP223;
        try {
            final int token = Integer.parseInt(parts[0]);
            isJEP223 = token != 1;
            if (isJEP223) {
                return token;
            }
            return Integer.parseInt(parts[1]);
        } catch (final Exception ex) {
            return 0;
        }
    }
}