Source Code for Apache Log4j Core Implementation

Apache Log4j Core Implementation provides the functional components of the logging system. Users are free to create their own plugins and include them in the logging configuration. Apache Log4j Core is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j Core Implementation is provided in a separate JAR file like log4j-core-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like and source package like You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 2.14.1 below.



 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the license for the specific language governing permissions and
 * limitations under the license.

package org.apache.logging.log4j.core.async;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.Constants;
import org.apache.logging.log4j.util.PropertiesUtil;

 * Strategy for deciding whether thread name should be cached or not.
public enum ThreadNameCachingStrategy { // LOG4J2-467
    CACHED {
        public String getThreadName() {
            String result = THREADLOCAL_NAME.get();
            if (result == null) {
                result = Thread.currentThread().getName();
            return result;
        public String getThreadName() {
            return Thread.currentThread().getName();

    private static final StatusLogger LOGGER = StatusLogger.getLogger();
    private static final ThreadLocal<String> THREADLOCAL_NAME = new ThreadLocal<>();
    static final ThreadNameCachingStrategy DEFAULT_STRATEGY = isAllocatingThreadGetName() ? CACHED : UNCACHED;

    abstract String getThreadName();

    public static ThreadNameCachingStrategy create() {
        final String name = PropertiesUtil.getProperties().getStringProperty("AsyncLogger.ThreadNameStrategy");
        try {
            final ThreadNameCachingStrategy result = name != null ? ThreadNameCachingStrategy.valueOf(name) : DEFAULT_STRATEGY;
            LOGGER.debug("AsyncLogger.ThreadNameStrategy={} (user specified {}, default is {})",
               , name,;
            return result;
        } catch (final Exception ex) {
            LOGGER.debug("Using AsyncLogger.ThreadNameStrategy.{}: '{}' not valid: {}",
               , name, ex.toString());
            return DEFAULT_STRATEGY;

    static boolean isAllocatingThreadGetName() {
        // LOG4J2-2052, LOG4J2-2635 JDK 8u102 ("1.8.0_102") removed the String allocation in Thread.getName()
        if (Constants.JAVA_MAJOR_VERSION == 8) {
            try {
                Pattern javaVersionPattern = Pattern.compile("(\\d+)\\.(\\d+)\\.(\\d+)_(\\d+)");
                Matcher m = javaVersionPattern.matcher(System.getProperty("java.version"));
                if (m.matches()) {
                    return Integer.parseInt( == 0 && Integer.parseInt( < 102;
                return true;
            } catch (Exception e) {
                return true;
        } else {
            return Constants.JAVA_MAJOR_VERSION < 8;



Or download all of them as a single archive file:

File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06


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