Apache Log4j JDK Logging Adapter is a custom implementation of java.util.logging.LogManager that uses Log4j. This adapter can be used with either the Log4j API or Log4j Core.

Bytecode (Java 8) for Apache Log4j JDK Logging Adapter is provided in a separate JAR file like log4j-jul-2.14.1.jar.

Source Code files for Apache Log4j API are provided in both binary packge like apache-log4j-2.14.1-bin.zip and source package like apache-log4j-2.14.1-src.zip. You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j JDK Logging Adapter 2.14.1 below.

⏎ org/apache/logging/log4j/jul/LevelTranslator.java

/*
 * 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.jul;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.LoaderUtil;
import org.apache.logging.log4j.util.PropertiesUtil;

/**
 * Utility class to convert between JDK Levels and Log4j 2 Levels.
 *
 * @since 2.1
 */
public final class LevelTranslator {

    /**
     * Custom Log4j level corresponding to the {@link java.util.logging.Level#FINEST} logging level. This maps to a
     * level more specific than {@link org.apache.logging.log4j.Level#TRACE}.
     */
    public static final Level FINEST = Level.forName("FINEST", Level.TRACE.intLevel() + 100);

    /**
     * Custom Log4j level corresponding to the {@link java.util.logging.Level#CONFIG} logging level. This maps to a
     * level in between {@link org.apache.logging.log4j.Level#INFO} and {@link org.apache.logging.log4j.Level#DEBUG}.
     */
    public static final Level CONFIG = Level.forName("CONFIG", Level.INFO.intLevel() + 50);

    private static final Logger LOGGER = StatusLogger.getLogger();
    private static final LevelConverter LEVEL_CONVERTER;

    static {
        final String levelConverterClassName =
            PropertiesUtil.getProperties().getStringProperty(Constants.LEVEL_CONVERTER_PROPERTY);
        if (levelConverterClassName != null) {
            LevelConverter levelConverter;
            try {
                levelConverter = LoaderUtil.newCheckedInstanceOf(levelConverterClassName, LevelConverter.class);
            } catch (final Exception e) {
                LOGGER.error("Could not create custom LevelConverter [{}].", levelConverterClassName, e);
                levelConverter = new DefaultLevelConverter();
            }
            LEVEL_CONVERTER = levelConverter;
        } else {
            LEVEL_CONVERTER = new DefaultLevelConverter();
        }
    }

    /**
     * Converts a JDK logging Level to a Log4j logging Level.
     *
     * @param level JDK Level to convert, may be null per the JUL specification.
     * @return converted Level or null
     */
    public static Level toLevel(final java.util.logging.Level level) {
        return LEVEL_CONVERTER.toLevel(level);
    }

    /**
     * Converts a Log4j logging Level to a JDK logging Level.
     *
     * @param level Log4j Level to convert.
     * @return converted Level.
     */
    public static java.util.logging.Level toJavaLevel(final Level level) {
        return LEVEL_CONVERTER.toJavaLevel(level);
    }

    private LevelTranslator() {
    }
}

⏎ org/apache/logging/log4j/jul/LevelTranslator.java

Or download all of them as a single archive file:

File name: log4j-jul-2.14.1-sources.jar
File size: 24567 bytes
Release date: 2021-03-06
Download 

⇒ Source Code for Apache Log4j Commons Logging Bridge

⇐ Source Code for Apache Log4j Core Implementation

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j