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/layout/JacksonFactory.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.layout;

import java.util.HashSet;
import java.util.Set;

import javax.xml.stream.XMLStreamException;

import org.apache.logging.log4j.core.impl.Log4jLogEvent;
import org.apache.logging.log4j.core.jackson.JsonConstants;
import org.apache.logging.log4j.core.jackson.Log4jJsonObjectMapper;
import org.apache.logging.log4j.core.jackson.Log4jXmlObjectMapper;
import org.apache.logging.log4j.core.jackson.Log4jYamlObjectMapper;
import org.apache.logging.log4j.core.jackson.XmlConstants;
import org.codehaus.stax2.XMLStreamWriter2;

import com.fasterxml.jackson.core.PrettyPrinter;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
import com.fasterxml.jackson.core.util.MinimalPrettyPrinter;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.ObjectWriter;
import com.fasterxml.jackson.databind.ser.impl.SimpleBeanPropertyFilter;
import com.fasterxml.jackson.databind.ser.impl.SimpleFilterProvider;
import com.fasterxml.jackson.dataformat.xml.util.DefaultXmlPrettyPrinter;

abstract class JacksonFactory {

    static class JSON extends JacksonFactory {

        private final boolean encodeThreadContextAsList;
        private final boolean includeStacktrace;
        private final boolean stacktraceAsString;
        private final boolean objectMessageAsJsonObject;

        public JSON(final boolean encodeThreadContextAsList, final boolean includeStacktrace, final boolean stacktraceAsString, final boolean objectMessageAsJsonObject) {
            this.encodeThreadContextAsList = encodeThreadContextAsList;
            this.includeStacktrace = includeStacktrace;
            this.stacktraceAsString = stacktraceAsString;
            this.objectMessageAsJsonObject = objectMessageAsJsonObject;
        }

        @Override
        protected String getPropertNameForContextMap() {
            return JsonConstants.ELT_CONTEXT_MAP;
        }

        @Override
        protected String getPropertyNameForTimeMillis() {
            return JsonConstants.ELT_TIME_MILLIS;
        }

        @Override
        protected String getPropertyNameForInstant() {
            return JsonConstants.ELT_INSTANT;
        }

        @Override
        protected String getPropertNameForSource() {
            return JsonConstants.ELT_SOURCE;
        }

        @Override
        protected String getPropertNameForNanoTime() {
            return JsonConstants.ELT_NANO_TIME;
        }

        @Override
        protected PrettyPrinter newCompactPrinter() {
            return new MinimalPrettyPrinter();
        }

        @Override
        protected ObjectMapper newObjectMapper() {
            return new Log4jJsonObjectMapper(encodeThreadContextAsList, includeStacktrace, stacktraceAsString, objectMessageAsJsonObject);
        }

        @Override
        protected PrettyPrinter newPrettyPrinter() {
            return new DefaultPrettyPrinter();
        }

    }

    static class XML extends JacksonFactory {

        static final int DEFAULT_INDENT = 1;

        private final boolean includeStacktrace;
        private final boolean stacktraceAsString;


        public XML(final boolean includeStacktrace, final boolean stacktraceAsString) {
            this.includeStacktrace = includeStacktrace;
            this.stacktraceAsString = stacktraceAsString;
        }

        @Override
        protected String getPropertyNameForTimeMillis() {
            return XmlConstants.ELT_TIME_MILLIS;
        }

        @Override
        protected String getPropertyNameForInstant() {
            return XmlConstants.ELT_INSTANT;
        }

        @Override
        protected String getPropertNameForContextMap() {
            return XmlConstants.ELT_CONTEXT_MAP;
        }

        @Override
        protected String getPropertNameForSource() {
            return XmlConstants.ELT_SOURCE;
        }

        @Override
        protected String getPropertNameForNanoTime() {
            return JsonConstants.ELT_NANO_TIME;
        }

        @Override
        protected PrettyPrinter newCompactPrinter() {
            // Yes, null is the proper answer.
            return null;
        }

        @Override
        protected ObjectMapper newObjectMapper() {
            return new Log4jXmlObjectMapper(includeStacktrace, stacktraceAsString);
        }

        @Override
        protected PrettyPrinter newPrettyPrinter() {
            return new Log4jXmlPrettyPrinter(DEFAULT_INDENT);
        }
    }

    static class YAML extends JacksonFactory {

        private final boolean includeStacktrace;
        private final boolean stacktraceAsString;


        public YAML(final boolean includeStacktrace, final boolean stacktraceAsString) {
            this.includeStacktrace = includeStacktrace;
            this.stacktraceAsString = stacktraceAsString;
        }

        @Override
        protected String getPropertyNameForTimeMillis() {
            return JsonConstants.ELT_TIME_MILLIS;
        }

        @Override
        protected String getPropertyNameForInstant() {
            return JsonConstants.ELT_INSTANT;
        }

        @Override
        protected String getPropertNameForContextMap() {
            return JsonConstants.ELT_CONTEXT_MAP;
        }

        @Override
        protected String getPropertNameForSource() {
            return JsonConstants.ELT_SOURCE;
        }

        @Override
        protected String getPropertNameForNanoTime() {
            return JsonConstants.ELT_NANO_TIME;
        }

        @Override
        protected PrettyPrinter newCompactPrinter() {
            return new MinimalPrettyPrinter();
        }

        @Override
        protected ObjectMapper newObjectMapper() {
            return new Log4jYamlObjectMapper(false, includeStacktrace, stacktraceAsString);
        }

        @Override
        protected PrettyPrinter newPrettyPrinter() {
            return new DefaultPrettyPrinter();
        }
    }

    /**
     * When <Event>s are written into a XML file; the "Event" object is not the root element, but an element named
     * <Events> created using {@link XmlLayout#getHeader()} and {@link XmlLayout#getFooter()} methods.
     * <p>
     * {@link com.fasterxml.jackson.dataformat.xml.util.DefaultXmlPrettyPrinter} is used to print the Event object into
     * XML; hence it assumes &lt;Event&gt; tag as the root element, so it prints the &lt;Event&gt; tag without any
     * indentation. To add an indentation to the &lt;Event&gt; tag; hence an additional indentation for any
     * sub-elements, this class is written. As an additional task, to avoid the blank line printed after the ending
     * &lt;/Event&gt; tag, {@link #writePrologLinefeed(XMLStreamWriter2)} method is also overridden.
     * </p>
     */
    static class Log4jXmlPrettyPrinter extends DefaultXmlPrettyPrinter {

        private static final long serialVersionUID = 1L;

        Log4jXmlPrettyPrinter(final int nesting) {
            _nesting = nesting;
        }

        @Override
        public void writePrologLinefeed(final XMLStreamWriter2 sw) throws XMLStreamException {
            // nothing
        }

        /**
         * Sets the nesting level to 1 rather than 0, so the "Event" tag will get indentation of next level below root.
         */
        @Override
        public DefaultXmlPrettyPrinter createInstance() {
            return new Log4jXmlPrettyPrinter(XML.DEFAULT_INDENT);
        }

    }

    abstract protected String getPropertyNameForTimeMillis();

    abstract protected String getPropertyNameForInstant();

    abstract protected String getPropertNameForContextMap();

    abstract protected String getPropertNameForSource();

    abstract protected String getPropertNameForNanoTime();

    abstract protected PrettyPrinter newCompactPrinter();

    abstract protected ObjectMapper newObjectMapper();

    abstract protected PrettyPrinter newPrettyPrinter();

    ObjectWriter newWriter(final boolean locationInfo, final boolean properties, final boolean compact) {
        return newWriter(locationInfo, properties, compact, false);
    }

    ObjectWriter newWriter(final boolean locationInfo, final boolean properties, final boolean compact,
            final boolean includeMillis) {
        final SimpleFilterProvider filters = new SimpleFilterProvider();
        final Set<String> except = new HashSet<>(3);
        if (!locationInfo) {
            except.add(this.getPropertNameForSource());
        }
        if (!properties) {
            except.add(this.getPropertNameForContextMap());
        }
        if (includeMillis) {
            except.add(getPropertyNameForInstant());
        } else {
            except.add(getPropertyNameForTimeMillis());
        }
        except.add(this.getPropertNameForNanoTime());
        filters.addFilter(Log4jLogEvent.class.getName(), SimpleBeanPropertyFilter.serializeAllExcept(except));
        final ObjectWriter writer = this.newObjectMapper().writer(compact ? this.newCompactPrinter() : this.newPrettyPrinter());
        return writer.with(filters);
    }

}

⏎ org/apache/logging/log4j/core/layout/JacksonFactory.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
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