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/pattern/EncodingPatternConverter.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.pattern;

import java.util.List;

import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.util.EnglishEnums;
import org.apache.logging.log4j.util.PerformanceSensitive;
import org.apache.logging.log4j.util.StringBuilders;

/**
 * Converter that encodes the output from a pattern using a specified format. Supported formats include HTML
 * (default) and JSON.
 */
@Plugin(name = "encode", category = PatternConverter.CATEGORY)
@ConverterKeys({"enc", "encode"})
@PerformanceSensitive("allocation")
public final class EncodingPatternConverter extends LogEventPatternConverter {

    private final List<PatternFormatter> formatters;
    private final EscapeFormat escapeFormat;

    /**
     * Private constructor.
     *
     * @param formatters   the PatternFormatters to generate the text to manipulate.
     * @param escapeFormat the escape format strategy to use for encoding output of formatters
     */
    private EncodingPatternConverter(final List<PatternFormatter> formatters,
                                     final EscapeFormat escapeFormat) {
        super("encode", "encode");
        this.formatters = formatters;
        this.escapeFormat = escapeFormat;
    }

    /**
     * Creates an EncodingPatternConverter using a pattern string and an optional escape format.
     *
     * @param config  the current Configuration
     * @param options first option is the nested pattern format; second option is the escape format (optional)
     * @return instance of pattern converter.
     */
    public static EncodingPatternConverter newInstance(final Configuration config, final String[] options) {
        if (options.length > 2 || options.length == 0) {
            LOGGER.error("Incorrect number of options on escape. Expected 1 or 2, but received {}",
                options.length);
            return null;
        }
        if (options[0] == null) {
            LOGGER.error("No pattern supplied on escape");
            return null;
        }
        final EscapeFormat escapeFormat = options.length < 2 ? EscapeFormat.HTML
            : EnglishEnums.valueOf(EscapeFormat.class, options[1], EscapeFormat.HTML);
        final PatternParser parser = PatternLayout.createPatternParser(config);
        final List<PatternFormatter> formatters = parser.parse(options[0]);
        return new EncodingPatternConverter(formatters, escapeFormat);
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void format(final LogEvent event, final StringBuilder toAppendTo) {
        final int start = toAppendTo.length();
        for (int i = 0; i < formatters.size(); i++) {
            formatters.get(i).format(event, toAppendTo);
        }
        escapeFormat.escape(toAppendTo, start);
    }

    private enum EscapeFormat {
        HTML {
            @Override
            void escape(final StringBuilder toAppendTo, final int start) {
                for (int i = toAppendTo.length() - 1; i >= start; i--) { // backwards: length may change
                    final char c = toAppendTo.charAt(i);
                    switch (c) {
                        case '\r':
                            toAppendTo.setCharAt(i, '\\');
                            toAppendTo.insert(i + 1, 'r');
                            break;
                        case '\n':
                            toAppendTo.setCharAt(i, '\\');
                            toAppendTo.insert(i + 1, 'n');
                            break;
                        case '&':
                            toAppendTo.setCharAt(i, '&');
                            toAppendTo.insert(i + 1, "amp;");
                            break;
                        case '<':
                            toAppendTo.setCharAt(i, '&');
                            toAppendTo.insert(i + 1, "lt;");
                            break;
                        case '>':
                            toAppendTo.setCharAt(i, '&');
                            toAppendTo.insert(i + 1, "gt;");
                            break;
                        case '"':
                            toAppendTo.setCharAt(i, '&');
                            toAppendTo.insert(i + 1, "quot;");
                            break;
                        case '\'':
                            toAppendTo.setCharAt(i, '&');
                            toAppendTo.insert(i + 1, "apos;");
                            break;
                        case '/':
                            toAppendTo.setCharAt(i, '&');
                            toAppendTo.insert(i + 1, "#x2F;");
                            break;
                    }
                }
            }
        },

        /**
         * JSON string escaping as defined in RFC 4627.
         *
         * @see <a href="https://www.ietf.org/rfc/rfc4627.txt">RFC 4627</a>
         */
        JSON {
            @Override
            void escape(final StringBuilder toAppendTo, final int start) {
                StringBuilders.escapeJson(toAppendTo, start);
            }
        },

        CRLF {
            @Override
            void escape(final StringBuilder toAppendTo, final int start) {
                for (int i = toAppendTo.length() - 1; i >= start; i--) { // backwards: length may change
                    final char c = toAppendTo.charAt(i);
                    switch (c) {
                        case '\r':
                            toAppendTo.setCharAt(i, '\\');
                            toAppendTo.insert(i + 1, 'r');
                            break;
                        case '\n':
                            toAppendTo.setCharAt(i, '\\');
                            toAppendTo.insert(i + 1, 'n');
                            break;
                    }
                }
            }
        },

        /**
         * XML string escaping as defined in XML specification.
         *
         * @see <a href="https://www.w3.org/TR/xml/">XML specification</a>
         */
        XML {
            @Override
            void escape(final StringBuilder toAppendTo, final int start) {
                StringBuilders.escapeXml(toAppendTo, start);
            }
        };

        /**
         * Escapes text using a standardized format from a given starting point to the end of the string.
         *
         * @param toAppendTo string buffer to escape
         * @param start      where to start escaping from
         */
        abstract void escape(final StringBuilder toAppendTo, final int start);
    }
}

⏎ org/apache/logging/log4j/core/pattern/EncodingPatternConverter.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 

⇒ Source Code for Apache Log4j JDK Logging Adapter

⇐ Source Code for Apache Log4j API

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j