Source Code for Apache Log4j API

Apache Log4j API provides the interface that applications should code to and provides the adapter components required for implementers to create a logging implementation. Apache Log4j API is a required module to use Apache Log4j.

Bytecode (Java 8) for Apache Log4j API is provided in a separate JAR file like log4j-api-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 API 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.util;

import java.util.Objects;
import java.util.Properties;

 * PropertySource backed by the current system properties. Other than having a
 * higher priority over normal properties, this follows the same rules as
 * {@link PropertiesPropertySource}.
 * @since 2.10.0
public class SystemPropertiesPropertySource implements PropertySource {

	private static final int DEFAULT_PRIORITY = 100;
	private static final String PREFIX = "log4j2.";

	public int getPriority() {

	public void forEach(final BiConsumer<String, String> action) {
		Properties properties;
		try {
			properties = System.getProperties();
		} catch (final SecurityException e) {
			// (1) There is no status logger.
			// (2) LowLevelLogUtil also consults system properties ("line.separator") to
			// open a BufferedWriter, so this may fail as well. Just having a hard reference
			// in this code to LowLevelLogUtil would cause a problem.
			// (3) We could log to System.err (nah) or just be quiet as we do now.
		// Lock properties only long enough to get a thread-safe SAFE snapshot of its
		// current keys, an array.
		final Object[] keySet;
		synchronized (properties) {
			keySet = properties.keySet().toArray();
		// Then traverse for an unknown amount of time.
		// Some keys may now be absent, in which case, the value is null.
		for (final Object key : keySet) {
			final String keyStr = Objects.toString(key, null);
			action.accept(keyStr, properties.getProperty(keyStr));

	public CharSequence getNormalForm(final Iterable<? extends CharSequence> tokens) {
		return PREFIX + Util.joinAsCamelCase(tokens);




Or download all of them as a single archive file:

File name: log4j-api-2.14.1-sources.jar
File size: 264773 bytes
Release date: 2021-03-06


Source Code for Apache Log4j Core Implementation

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