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.appender.rewrite;

import java.util.HashMap;
import java.util.Locale;
import java.util.Map;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.core.Core;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.impl.Log4jLogEvent;
import org.apache.logging.log4j.core.util.KeyValuePair;

 * Rewrites log event levels for a given logger name.
 * @since 2.4
@Plugin(name = "LoggerNameLevelRewritePolicy", category = Core.CATEGORY_NAME, elementType = "rewritePolicy", printObject = true)
public class LoggerNameLevelRewritePolicy implements RewritePolicy {

     * Creates a policy to rewrite levels for a given logger name.
     * @param loggerNamePrefix
     *        The logger name prefix for events to rewrite; all event logger names that start with this string will be
     *        rewritten.
     * @param levelPairs
     *        The levels to rewrite, the key is the source level, the value the target level.
     * @return a new LoggerNameLevelRewritePolicy
    public static LoggerNameLevelRewritePolicy createPolicy(
            // @formatter:off
            @PluginAttribute("logger") final String loggerNamePrefix,
            @PluginElement("KeyValuePair") final KeyValuePair[] levelPairs) {
            // @formatter:on
        final Map<Level, Level> newMap = new HashMap<>(levelPairs.length);
        for (final KeyValuePair keyValuePair : levelPairs) {
            newMap.put(getLevel(keyValuePair.getKey()), getLevel(keyValuePair.getValue()));
        return new LoggerNameLevelRewritePolicy(loggerNamePrefix, newMap);

    private static Level getLevel(final String name) {
        return Level.getLevel(name.toUpperCase(Locale.ROOT));

    private final String loggerName;

    private final Map<Level, Level> map;

    private LoggerNameLevelRewritePolicy(final String loggerName, final Map<Level, Level> map) {
        this.loggerName = loggerName; = map;

    public LogEvent rewrite(final LogEvent event) {
        if (event.getLoggerName() == null || !event.getLoggerName().startsWith(loggerName)) {
            return event;
        final Level sourceLevel = event.getLevel();
        final Level newLevel = map.get(sourceLevel);
        if (newLevel == null || newLevel == sourceLevel) {
            return event;
        final LogEvent result = new Log4jLogEvent.Builder(event).setLevel(newLevel).build();
        return result;




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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