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/jmx/Server.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.jmx;

import java.lang.management.ManagementFactory;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import javax.management.InstanceAlreadyExistsException;
import javax.management.InstanceNotFoundException;
import javax.management.MBeanRegistrationException;
import javax.management.MBeanServer;
import javax.management.NotCompliantMBeanException;
import javax.management.ObjectName;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.LoggerContext;
import org.apache.logging.log4j.core.appender.AsyncAppender;
import org.apache.logging.log4j.core.async.AsyncLoggerConfig;
import org.apache.logging.log4j.core.async.AsyncLoggerContext;
import org.apache.logging.log4j.core.config.LoggerConfig;
import org.apache.logging.log4j.core.impl.Log4jContextFactory;
import org.apache.logging.log4j.core.selector.ContextSelector;
import org.apache.logging.log4j.core.util.Constants;
import org.apache.logging.log4j.core.util.Log4jThreadFactory;
import org.apache.logging.log4j.spi.LoggerContextFactory;
import org.apache.logging.log4j.status.StatusLogger;
import org.apache.logging.log4j.util.PropertiesUtil;

/**
 * Creates MBeans to instrument various classes in the log4j class hierarchy.
 * <p>
 * All instrumentation for Log4j 2 classes can be disabled by setting system property {@code -Dlog4j2.disable.jmx=true}.
 * </p>
 */
public final class Server {

    private static final String CONTEXT_NAME_ALL = "*";
	/**
     * The domain part, or prefix ({@value}) of the {@code ObjectName} of all MBeans that instrument Log4J2 components.
     */
    public static final String DOMAIN = "org.apache.logging.log4j2";
    private static final String PROPERTY_DISABLE_JMX = "log4j2.disable.jmx";
    private static final String PROPERTY_ASYNC_NOTIF = "log4j2.jmx.notify.async";
    private static final String THREAD_NAME_PREFIX = "jmx.notif";
    private static final StatusLogger LOGGER = StatusLogger.getLogger();
    static final Executor executor = isJmxDisabled() ? null : createExecutor();

    private Server() {
    }

    /**
     * Returns either a {@code null} Executor (causing JMX notifications to be sent from the caller thread) or a daemon
     * background thread Executor, depending on the value of system property "log4j2.jmx.notify.async". If this
     * property is not set, use a {@code null} Executor for web apps to avoid memory leaks and other issues when the
     * web app is restarted.
     * @see <a href="https://issues.apache.org/jira/browse/LOG4J2-938">LOG4J2-938</a>
     */
    private static ExecutorService createExecutor() {
        final boolean defaultAsync = !Constants.IS_WEB_APP;
        final boolean async = PropertiesUtil.getProperties().getBooleanProperty(PROPERTY_ASYNC_NOTIF, defaultAsync);
        return async ? Executors.newFixedThreadPool(1, Log4jThreadFactory.createDaemonThreadFactory(THREAD_NAME_PREFIX))
                : null;
    }

    /**
     * Either returns the specified name as is, or returns a quoted value containing the specified name with the special
     * characters (comma, equals, colon, quote, asterisk, or question mark) preceded with a backslash.
     *
     * @param name the name to escape so it can be used as a value in an {@link ObjectName}.
     * @return the escaped name
     */
    public static String escape(final String name) {
        final StringBuilder sb = new StringBuilder(name.length() * 2);
        boolean needsQuotes = false;
        for (int i = 0; i < name.length(); i++) {
            final char c = name.charAt(i);
            switch (c) {
            case '\\':
            case '*':
            case '?':
            case '\"':
                // quote, star, question & backslash must be escaped
                sb.append('\\');
                needsQuotes = true; // ... and can only appear in quoted value
                break;
            case ',':
            case '=':
            case ':':
                // no need to escape these, but value must be quoted
                needsQuotes = true;
                break;
            case '\r':
                // drop \r characters: \\r gives "invalid escape sequence"
                continue;
            case '\n':
                // replace \n characters with \\n sequence
                sb.append("\\n");
                needsQuotes = true;
                continue;
            }
            sb.append(c);
        }
        if (needsQuotes) {
            sb.insert(0, '\"');
            sb.append('\"');
        }
        return sb.toString();
    }

    private static boolean isJmxDisabled() {
        return PropertiesUtil.getProperties().getBooleanProperty(PROPERTY_DISABLE_JMX);
    }

    public static void reregisterMBeansAfterReconfigure() {
        // avoid creating Platform MBean Server if JMX disabled
        if (isJmxDisabled()) {
            LOGGER.debug("JMX disabled for Log4j2. Not registering MBeans.");
            return;
        }
        final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        reregisterMBeansAfterReconfigure(mbs);
    }

    public static void reregisterMBeansAfterReconfigure(final MBeanServer mbs) {
        if (isJmxDisabled()) {
            LOGGER.debug("JMX disabled for Log4j2. Not registering MBeans.");
            return;
        }

        // now provide instrumentation for the newly configured
        // LoggerConfigs and Appenders
        try {
            final ContextSelector selector = getContextSelector();
            if (selector == null) {
                LOGGER.debug("Could not register MBeans: no ContextSelector found.");
                return;
            }
            LOGGER.trace("Reregistering MBeans after reconfigure. Selector={}", selector);
            final List<LoggerContext> contexts = selector.getLoggerContexts();
            int i = 0;
            for (final LoggerContext ctx : contexts) {
                LOGGER.trace("Reregistering context ({}/{}): '{}' {}", ++i, contexts.size(), ctx.getName(), ctx);
                // first unregister the context and all nested loggers,
                // appenders, statusLogger, contextSelector, ringbuffers...
                unregisterLoggerContext(ctx.getName(), mbs);

                final LoggerContextAdmin mbean = new LoggerContextAdmin(ctx, executor);
                register(mbs, mbean, mbean.getObjectName());

                if (ctx instanceof AsyncLoggerContext) {
                    final RingBufferAdmin rbmbean = ((AsyncLoggerContext) ctx).createRingBufferAdmin();
                    if (rbmbean.getBufferSize() > 0) {
                    	// don't register if Disruptor not started (DefaultConfiguration: config not found)
                    	register(mbs, rbmbean, rbmbean.getObjectName());
                    }
                }

                // register the status logger and the context selector
                // repeatedly
                // for each known context: if one context is unregistered,
                // these MBeans should still be available for the other
                // contexts.
                registerStatusLogger(ctx.getName(), mbs, executor);
                registerContextSelector(ctx.getName(), selector, mbs, executor);

                registerLoggerConfigs(ctx, mbs, executor);
                registerAppenders(ctx, mbs, executor);
            }
        } catch (final Exception ex) {
            LOGGER.error("Could not register mbeans", ex);
        }
    }

    /**
     * Unregister all log4j MBeans from the platform MBean server.
     */
    public static void unregisterMBeans() {
        if (isJmxDisabled()) {
            LOGGER.debug("JMX disabled for Log4j2. Not unregistering MBeans.");
            return;
        }
        unregisterMBeans(ManagementFactory.getPlatformMBeanServer());
    }

    /**
     * Unregister all log4j MBeans from the specified MBean server.
     *
     * @param mbs the MBean server to unregister from.
     */
	public static void unregisterMBeans(final MBeanServer mbs) {
		if (mbs != null) {
			unregisterStatusLogger(CONTEXT_NAME_ALL, mbs);
			unregisterContextSelector(CONTEXT_NAME_ALL, mbs);
			unregisterContexts(mbs);
			unregisterLoggerConfigs(CONTEXT_NAME_ALL, mbs);
			unregisterAsyncLoggerRingBufferAdmins(CONTEXT_NAME_ALL, mbs);
			unregisterAsyncLoggerConfigRingBufferAdmins(CONTEXT_NAME_ALL, mbs);
			unregisterAppenders(CONTEXT_NAME_ALL, mbs);
			unregisterAsyncAppenders(CONTEXT_NAME_ALL, mbs);
		}
	}

    /**
     * Returns the {@code ContextSelector} of the current {@code Log4jContextFactory}.
     *
     * @return the {@code ContextSelector} of the current {@code Log4jContextFactory}
     */
    private static ContextSelector getContextSelector() {
        final LoggerContextFactory factory = LogManager.getFactory();
        if (factory instanceof Log4jContextFactory) {
            final ContextSelector selector = ((Log4jContextFactory) factory).getSelector();
            return selector;
        }
        return null;
    }

    /**
     * Unregisters all MBeans associated with the specified logger context (including MBeans for {@code LoggerConfig}s
     * and {@code Appender}s from the platform MBean server.
     *
     * @param loggerContextName name of the logger context to unregister
     */
    public static void unregisterLoggerContext(final String loggerContextName) {
        if (isJmxDisabled()) {
            LOGGER.debug("JMX disabled for Log4j2. Not unregistering MBeans.");
            return;
        }
        final MBeanServer mbs = ManagementFactory.getPlatformMBeanServer();
        unregisterLoggerContext(loggerContextName, mbs);
    }

    /**
     * Unregisters all MBeans associated with the specified logger context (including MBeans for {@code LoggerConfig}s
     * and {@code Appender}s from the platform MBean server.
     *
     * @param contextName name of the logger context to unregister
     * @param mbs the MBean Server to unregister the instrumented objects from
     */
    public static void unregisterLoggerContext(final String contextName, final MBeanServer mbs) {
        final String search = String.format(LoggerContextAdminMBean.PATTERN, escape(contextName), "*");
        unregisterAllMatching(search, mbs); // unregister context mbean

        // now unregister all MBeans associated with this logger context
        unregisterStatusLogger(contextName, mbs);
        unregisterContextSelector(contextName, mbs);
        unregisterLoggerConfigs(contextName, mbs);
        unregisterAppenders(contextName, mbs);
        unregisterAsyncAppenders(contextName, mbs);
        unregisterAsyncLoggerRingBufferAdmins(contextName, mbs);
        unregisterAsyncLoggerConfigRingBufferAdmins(contextName, mbs);
    }

    private static void registerStatusLogger(final String contextName, final MBeanServer mbs, final Executor executor)
            throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {

        final StatusLoggerAdmin mbean = new StatusLoggerAdmin(contextName, executor);
        register(mbs, mbean, mbean.getObjectName());
    }

    private static void registerContextSelector(final String contextName, final ContextSelector selector,
            final MBeanServer mbs, final Executor executor) throws InstanceAlreadyExistsException,
            MBeanRegistrationException, NotCompliantMBeanException {

        final ContextSelectorAdmin mbean = new ContextSelectorAdmin(contextName, selector);
        register(mbs, mbean, mbean.getObjectName());
    }

    private static void unregisterStatusLogger(final String contextName, final MBeanServer mbs) {
        final String search = String.format(StatusLoggerAdminMBean.PATTERN, escape(contextName), "*");
        unregisterAllMatching(search, mbs);
    }

    private static void unregisterContextSelector(final String contextName, final MBeanServer mbs) {
        final String search = String.format(ContextSelectorAdminMBean.PATTERN, escape(contextName), "*");
        unregisterAllMatching(search, mbs);
    }

    private static void unregisterLoggerConfigs(final String contextName, final MBeanServer mbs) {
        final String pattern = LoggerConfigAdminMBean.PATTERN;
        final String search = String.format(pattern, escape(contextName), "*");
        unregisterAllMatching(search, mbs);
    }

    private static void unregisterContexts(final MBeanServer mbs) {
        final String pattern = LoggerContextAdminMBean.PATTERN;
        final String search = String.format(pattern, "*");
        unregisterAllMatching(search, mbs);
    }

    private static void unregisterAppenders(final String contextName, final MBeanServer mbs) {
        final String pattern = AppenderAdminMBean.PATTERN;
        final String search = String.format(pattern, escape(contextName), "*");
        unregisterAllMatching(search, mbs);
    }

    private static void unregisterAsyncAppenders(final String contextName, final MBeanServer mbs) {
        final String pattern = AsyncAppenderAdminMBean.PATTERN;
        final String search = String.format(pattern, escape(contextName), "*");
        unregisterAllMatching(search, mbs);
    }

    private static void unregisterAsyncLoggerRingBufferAdmins(final String contextName, final MBeanServer mbs) {
        final String pattern1 = RingBufferAdminMBean.PATTERN_ASYNC_LOGGER;
        final String search1 = String.format(pattern1, escape(contextName));
        unregisterAllMatching(search1, mbs);
    }

    private static void unregisterAsyncLoggerConfigRingBufferAdmins(final String contextName, final MBeanServer mbs) {
        final String pattern2 = RingBufferAdminMBean.PATTERN_ASYNC_LOGGER_CONFIG;
        final String search2 = String.format(pattern2, escape(contextName), "*");
        unregisterAllMatching(search2, mbs);
    }

    private static void unregisterAllMatching(final String search, final MBeanServer mbs) {
        try {
            final ObjectName pattern = new ObjectName(search);
            final Set<ObjectName> found = mbs.queryNames(pattern, null);
            if (found == null || found.isEmpty()) {
            	LOGGER.trace("Unregistering but no MBeans found matching '{}'", search);
            } else {
            	LOGGER.trace("Unregistering {} MBeans: {}", found.size(), found);
            }
			if (found != null) {
				for (final ObjectName objectName : found) {
					mbs.unregisterMBean(objectName);
				}
			}
        } catch (final InstanceNotFoundException ex) {
            LOGGER.debug("Could not unregister MBeans for " + search + ". Ignoring " + ex);
        } catch (final Exception ex) {
            LOGGER.error("Could not unregister MBeans for " + search, ex);
        }
    }

    private static void registerLoggerConfigs(final LoggerContext ctx, final MBeanServer mbs, final Executor executor)
            throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {

        final Map<String, LoggerConfig> map = ctx.getConfiguration().getLoggers();
        for (final String name : map.keySet()) {
            final LoggerConfig cfg = map.get(name);
            final LoggerConfigAdmin mbean = new LoggerConfigAdmin(ctx, cfg);
            register(mbs, mbean, mbean.getObjectName());

            if (cfg instanceof AsyncLoggerConfig) {
                final AsyncLoggerConfig async = (AsyncLoggerConfig) cfg;
                final RingBufferAdmin rbmbean = async.createRingBufferAdmin(ctx.getName());
                register(mbs, rbmbean, rbmbean.getObjectName());
            }
        }
    }

    private static void registerAppenders(final LoggerContext ctx, final MBeanServer mbs, final Executor executor)
            throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {

        final Map<String, Appender> map = ctx.getConfiguration().getAppenders();
        for (final String name : map.keySet()) {
            final Appender appender = map.get(name);

            if (appender instanceof AsyncAppender) {
                final AsyncAppender async = ((AsyncAppender) appender);
                final AsyncAppenderAdmin mbean = new AsyncAppenderAdmin(ctx.getName(), async);
                register(mbs, mbean, mbean.getObjectName());
            } else {
                final AppenderAdmin mbean = new AppenderAdmin(ctx.getName(), appender);
                register(mbs, mbean, mbean.getObjectName());
            }
        }
    }

    private static void register(final MBeanServer mbs, final Object mbean, final ObjectName objectName)
            throws InstanceAlreadyExistsException, MBeanRegistrationException, NotCompliantMBeanException {
        LOGGER.debug("Registering MBean {}", objectName);
        mbs.registerMBean(mbean, objectName);
    }
}

⏎ org/apache/logging/log4j/core/jmx/Server.java

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File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06
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