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.util;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

 * Encodes Strings to bytes.
 * @since 2.5
public final class StringEncoder {

    private StringEncoder() {

     * Converts a String to a byte[].
     * @param str if null, return null.
     * @param charset if null, use the default charset.
     * @return a byte[]
    public static byte[] toBytes(final String str, final Charset charset) {
        if (str != null) {
            if (StandardCharsets.ISO_8859_1.equals(charset)) {
                return encodeSingleByteChars(str);
            final Charset actual = charset != null ? charset : Charset.defaultCharset();
            try { // LOG4J2-935: String.getBytes(String) gives better performance
                return str.getBytes(;
            } catch (final UnsupportedEncodingException e) {
                return str.getBytes(actual);
        return null;

     * Encodes the specified char sequence by casting each character to a byte.
     * @param s the char sequence to encode
     * @return the encoded String
     * @see <a href="">LOG4J2-1151</a>
    public static byte[] encodeSingleByteChars(final CharSequence s) {
        final int length = s.length();
        final byte[] result = new byte[length];
        encodeString(s, 0, length, result);
        return result;

    // LOG4J2-1151
     * Implementation note: this is the fast path. If the char array contains only ISO-8859-1 characters, all the work
     * will be done here.
    public static int encodeIsoChars(final CharSequence charArray, int charIndex, final byte[] byteArray, int byteIndex, final int length) {
        int i = 0;
        for (; i < length; i++) {
            final char c = charArray.charAt(charIndex++);
            if (c > 255) {
            byteArray[(byteIndex++)] = ((byte) c);
        return i;

    // LOG4J2-1151
    public static int encodeString(final CharSequence charArray, int charOffset, int charLength, final byte[] byteArray) {
        int byteOffset = 0;
        int length = Math.min(charLength, byteArray.length);
        int charDoneIndex = charOffset + length;
        while (charOffset < charDoneIndex) {
            final int done = encodeIsoChars(charArray, charOffset, byteArray, byteOffset, length);
            charOffset += done;
            byteOffset += done;
            if (done != length) {
                final char c = charArray.charAt(charOffset++);
                if ((Character.isHighSurrogate(c)) && (charOffset < charDoneIndex)
                        && (Character.isLowSurrogate(charArray.charAt(charOffset)))) {
                    if (charLength > byteArray.length) {
                byteArray[(byteOffset++)] = '?';
                length = Math.min(charDoneIndex - charOffset, byteArray.length - byteOffset);
        return byteOffset;



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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