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/util/WatcherFactory.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.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.util.List;
import java.util.Map;
import java.util.Objects;

import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.ConfigurationFileWatcher;
import org.apache.logging.log4j.core.config.ConfigurationListener;
import org.apache.logging.log4j.core.config.Reconfigurable;
import org.apache.logging.log4j.core.config.plugins.util.PluginManager;
import org.apache.logging.log4j.core.config.plugins.util.PluginType;
import org.apache.logging.log4j.status.StatusLogger;

/**
 * Creates Watchers of various types.
 */
public class WatcherFactory {

    private static Logger LOGGER = StatusLogger.getLogger();
    private static PluginManager pluginManager = new PluginManager(Watcher.CATEGORY);

    private static volatile WatcherFactory factory;

    private final Map<String, PluginType<?>> plugins;

    private WatcherFactory(List<String> packages) {
        pluginManager.collectPlugins(packages);
        plugins = pluginManager.getPlugins();
    }

    public static WatcherFactory getInstance(List<String> packages) {
        if (factory == null) {
            synchronized (pluginManager) {
                if (factory == null) {
                    factory = new WatcherFactory(packages);
                }
            }
        }
        return factory;
    }

    @SuppressWarnings("unchecked")
    public Watcher newWatcher(Source source, final Configuration configuration, final Reconfigurable reconfigurable,
        final List<ConfigurationListener> configurationListeners, long lastModifiedMillis) {
        if (source.getFile() != null) {
            return new ConfigurationFileWatcher(configuration, reconfigurable, configurationListeners,
                lastModifiedMillis);
        } else {
            String name = source.getURI().getScheme();
            PluginType<?> pluginType = plugins.get(name);
            if (pluginType != null) {
                return instantiate(name, (Class<? extends Watcher>) pluginType.getPluginClass(), configuration,
                    reconfigurable, configurationListeners, lastModifiedMillis);
            }
            LOGGER.info("No Watcher plugin is available for protocol '{}'", name);
            return null;
        }
    }

    public static <T extends Watcher> T instantiate(String name, final Class<T> clazz,
        final Configuration configuration, final Reconfigurable reconfigurable,
        final List<ConfigurationListener> listeners, long lastModifiedMillis) {
        Objects.requireNonNull(clazz, "No class provided");
        try {
            Constructor<T> constructor = clazz
                .getConstructor(Configuration.class, Reconfigurable.class, List.class, long.class);
            return constructor.newInstance(configuration, reconfigurable, listeners, lastModifiedMillis);
        } catch (NoSuchMethodException ex) {
            throw new IllegalArgumentException("No valid constructor for Watcher plugin " + name, ex);
        } catch (final LinkageError | InstantiationException e) {
            // LOG4J2-1051
            // On platforms like Google App Engine and Android, some JRE classes are not supported: JMX, JNDI, etc.
            throw new IllegalArgumentException(e);
        } catch (final IllegalAccessException e) {
            throw new IllegalStateException(e);
        } catch (final InvocationTargetException e) {
            Throwables.rethrow(e.getCause());
            throw new InternalError("Unreachable");
        }
    }
}

⏎ org/apache/logging/log4j/core/util/WatcherFactory.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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