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/appender/rewrite/RewriteAppender.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.appender.rewrite;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Core;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.AppenderControl;
import org.apache.logging.log4j.core.config.AppenderRef;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginConfiguration;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.util.Booleans;

/**
 * This Appender allows the logging event to be manipulated before it is processed by other Appenders.
 */
@Plugin(name = "Rewrite", category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE, printObject = true)
public final class RewriteAppender extends AbstractAppender {

    private final Configuration config;
    private final ConcurrentMap<String, AppenderControl> appenders = new ConcurrentHashMap<>();
    private final RewritePolicy rewritePolicy;
    private final AppenderRef[] appenderRefs;

    private RewriteAppender(final String name, final Filter filter, final boolean ignoreExceptions,
                            final AppenderRef[] appenderRefs, final RewritePolicy rewritePolicy,
                            final Configuration config, final Property[] properties) {
        super(name, filter, null, ignoreExceptions, properties);
        this.config = config;
        this.rewritePolicy = rewritePolicy;
        this.appenderRefs = appenderRefs;
    }

    @Override
    public void start() {
        for (final AppenderRef ref : appenderRefs) {
            final String name = ref.getRef();
            final Appender appender = config.getAppender(name);
            if (appender != null) {
                final Filter filter = appender instanceof AbstractAppender ?
                    ((AbstractAppender) appender).getFilter() : null;
                appenders.put(name, new AppenderControl(appender, ref.getLevel(), filter));
            } else {
                LOGGER.error("Appender " + ref + " cannot be located. Reference ignored");
            }
        }
        super.start();
    }

    /**
     * Modifies the event and pass to the subordinate Appenders.
     * @param event The LogEvent.
     */
    @Override
    public void append(LogEvent event) {
        if (rewritePolicy != null) {
            event = rewritePolicy.rewrite(event);
        }
        for (final AppenderControl control : appenders.values()) {
            control.callAppender(event);
        }
    }

    /**
     * Creates a RewriteAppender.
     * @param name The name of the Appender.
     * @param ignore If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
     *               they are propagated to the caller.
     * @param appenderRefs An array of Appender names to call.
     * @param config The Configuration.
     * @param rewritePolicy The policy to use to modify the event.
     * @param filter A Filter to filter events.
     * @return The created RewriteAppender.
     */
    @PluginFactory
    public static RewriteAppender createAppender(
            @PluginAttribute("name") final String name,
            @PluginAttribute("ignoreExceptions") final String ignore,
            @PluginElement("AppenderRef") final AppenderRef[] appenderRefs,
            @PluginConfiguration final Configuration config,
            @PluginElement("RewritePolicy") final RewritePolicy rewritePolicy,
            @PluginElement("Filter") final Filter filter) {

        final boolean ignoreExceptions = Booleans.parseBoolean(ignore, true);
        if (name == null) {
            LOGGER.error("No name provided for RewriteAppender");
            return null;
        }
        if (appenderRefs == null) {
            LOGGER.error("No appender references defined for RewriteAppender");
            return null;
        }
        return new RewriteAppender(name, filter, ignoreExceptions, appenderRefs, rewritePolicy, config, null);
    }
}

⏎ org/apache/logging/log4j/core/appender/rewrite/RewriteAppender.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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