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/osgi/Activator.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.osgi;

import java.util.Collection;
import java.util.Hashtable;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.apache.logging.log4j.core.config.plugins.util.PluginRegistry;
import org.apache.logging.log4j.core.impl.Log4jProvider;
import org.apache.logging.log4j.core.impl.ThreadContextDataInjector;
import org.apache.logging.log4j.core.impl.ThreadContextDataProvider;
import org.apache.logging.log4j.core.util.Constants;
import org.apache.logging.log4j.core.util.ContextDataProvider;
import org.apache.logging.log4j.spi.Provider;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;
import org.osgi.framework.Bundle;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.BundleEvent;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.framework.ServiceReference;
import org.osgi.framework.ServiceRegistration;
import org.osgi.framework.SynchronousBundleListener;
import org.osgi.framework.wiring.BundleWiring;

/**
 * OSGi BundleActivator.
 */
public final class Activator implements BundleActivator, SynchronousBundleListener {

    private static final Logger LOGGER = StatusLogger.getLogger();

    private final AtomicReference<BundleContext> contextRef = new AtomicReference<>();

    ServiceRegistration provideRegistration = null;
    ServiceRegistration contextDataRegistration = null;

    @Override
    public void start(final BundleContext context) throws Exception {
        final Provider provider = new Log4jProvider();
        final Hashtable<String, String> props = new Hashtable<>();
        props.put("APIVersion", "2.60");
        final ContextDataProvider threadContextProvider = new ThreadContextDataProvider();
        provideRegistration = context.registerService(Provider.class.getName(), provider, props);
        contextDataRegistration = context.registerService(ContextDataProvider.class.getName(), threadContextProvider,
                null);
        loadContextProviders(context);
        // allow the user to override the default ContextSelector (e.g., by using BasicContextSelector for a global cfg)
        if (PropertiesUtil.getProperties().getStringProperty(Constants.LOG4J_CONTEXT_SELECTOR) == null) {
            System.setProperty(Constants.LOG4J_CONTEXT_SELECTOR, BundleContextSelector.class.getName());
        }
        if (this.contextRef.compareAndSet(null, context)) {
            context.addBundleListener(this);
            // done after the BundleListener as to not miss any new bundle installs in the interim
            scanInstalledBundlesForPlugins(context);
        }
    }

    private static void scanInstalledBundlesForPlugins(final BundleContext context) {
        final Bundle[] bundles = context.getBundles();
        for (final Bundle bundle : bundles) {
            // TODO: bundle state can change during this
            scanBundleForPlugins(bundle);
        }
    }

    private static void scanBundleForPlugins(final Bundle bundle) {
        final long bundleId = bundle.getBundleId();
        // LOG4J2-920: don't scan system bundle for plugins
        if (bundle.getState() == Bundle.ACTIVE && bundleId != 0) {
            LOGGER.trace("Scanning bundle [{}, id=%d] for plugins.", bundle.getSymbolicName(), bundleId);
            PluginRegistry.getInstance().loadFromBundle(bundleId,
                    bundle.adapt(BundleWiring.class).getClassLoader());
        }
    }

    private static void loadContextProviders(final BundleContext bundleContext) {
        try {
            final Collection<ServiceReference<ContextDataProvider>> serviceReferences =
                    bundleContext.getServiceReferences(ContextDataProvider.class, null);
            for (final ServiceReference<ContextDataProvider> serviceReference : serviceReferences) {
                final ContextDataProvider provider = bundleContext.getService(serviceReference);
                ThreadContextDataInjector.contextDataProviders.add(provider);
            }
        } catch (final InvalidSyntaxException ex) {
            LOGGER.error("Error accessing context data provider", ex);
        }
    }

    private static void stopBundlePlugins(final Bundle bundle) {
        LOGGER.trace("Stopping bundle [{}] plugins.", bundle.getSymbolicName());
        // TODO: plugin lifecycle code
        PluginRegistry.getInstance().clearBundlePlugins(bundle.getBundleId());
    }

    @Override
    public void stop(final BundleContext context) throws Exception {
        provideRegistration.unregister();
        contextDataRegistration.unregister();
        this.contextRef.compareAndSet(context, null);
        LogManager.shutdown();
    }

    @Override
    public void bundleChanged(final BundleEvent event) {
        switch (event.getType()) {
            // FIXME: STARTING instead of STARTED?
            case BundleEvent.STARTED:
                scanBundleForPlugins(event.getBundle());
                break;

            case BundleEvent.STOPPING:
                stopBundlePlugins(event.getBundle());
                break;

            default:
                break;
        }
    }
}

⏎ org/apache/logging/log4j/core/osgi/Activator.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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