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 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 Core Implementation 2.14.1 below.

⏎ org/apache/logging/log4j/core/lookup/EventLookup.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.core.lookup;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.plugins.Plugin;

/**
 * Looks up values from the log event.
 */
@Plugin(name = "event", category = StrLookup.CATEGORY)
public class EventLookup extends AbstractLookup {

    /**
     * Looks up the value from the logging event.
     * @param event The current LogEvent.
     * @param key  the key to be looked up.
     * @return The value of the specified log event field.
     */
    @Override
    public String lookup(final LogEvent event, final String key) {
        switch (key) {
            case "Marker": {
                return event.getMarker() != null ? event.getMarker().getName() : null;
            }
            case "ThreadName": {
                return event.getThreadName();
            }
            case "Level": {
                return event.getLevel().toString();
            }
            case "ThreadId": {
                return Long.toString(event.getThreadId());
            }
            case "Timestamp": {
                return Long.toString(event.getTimeMillis());
            }
            case "Exception": {
                if (event.getThrown() != null) {
                    return event.getThrown().getClass().getSimpleName();
                }
                if (event.getThrownProxy() != null) {
                    return event.getThrownProxy().getName();
                }
                return null;
            }
            case "Logger": {
                return event.getLoggerName();
            }
            case "Message": {
                return event.getMessage().getFormattedMessage();
            }
            default: {
                return null;
            }
        }
    }
}

⏎ org/apache/logging/log4j/core/lookup/EventLookup.java

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
Download 

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