Source Code for Apache Log4j Tag Library

Apache Log4j Tag Library creates the capability of inserting log statements in JSPs without the use of Java scripting.

Bytecode (Java 8) for Apache Log4j Tag Library is provided in a separate JAR file like log4j-taglib-2.14.1.jar.

Source Code files for Apache Log4j IOStreams are provided in both binary packge like and source package like You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Tag Library 2.14.1 below.



 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the license for the specific language governing permissions and
 * limitations under the license.
package org.apache.logging.log4j.taglib;

import java.util.WeakHashMap;

import javax.servlet.ServletContext;

import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.message.MessageFactory;
import org.apache.logging.log4j.spi.AbstractLogger;
import org.apache.logging.log4j.spi.ExtendedLogger;
import org.apache.logging.log4j.spi.LoggerContext;
import org.apache.logging.log4j.spi.LoggerRegistry;

 * This bridge between the tag library and the Log4j API ensures that instances of {@link Log4jTaglibLogger} are
 * appropriately held in memory and not constantly recreated.
 * @since 2.0
final class Log4jTaglibLoggerContext implements LoggerContext {
    // These were change to WeakHashMaps to avoid ClassLoader (memory) leak, something that's particularly
    // important in Servlet containers.
    private static final WeakHashMap<ServletContext, Log4jTaglibLoggerContext> CONTEXTS = new WeakHashMap<>();

    private final LoggerRegistry<Log4jTaglibLogger> loggerRegistry = new LoggerRegistry<>(
            new LoggerRegistry.WeakMapFactory<Log4jTaglibLogger>());

    private final ServletContext servletContext;

    private Log4jTaglibLoggerContext(final ServletContext servletContext) {
        this.servletContext = servletContext;

    public Object getExternalContext() {
        return this.servletContext;

    public Log4jTaglibLogger getLogger(final String name) {
        return this.getLogger(name, null);

    public Log4jTaglibLogger getLogger(final String name, final MessageFactory messageFactory) {
        // Note: This is the only method where we add entries to the 'loggerRegistry' ivar.
        Log4jTaglibLogger logger = this.loggerRegistry.getLogger(name, messageFactory);
        if (logger != null) {
            AbstractLogger.checkMessageFactory(logger, messageFactory);
            return logger;

        synchronized (this.loggerRegistry) {
            logger = this.loggerRegistry.getLogger(name, messageFactory);
            if (logger == null) {
                final LoggerContext context = LogManager.getContext(false);
                final ExtendedLogger original = messageFactory == null ?
                        context.getLogger(name) : context.getLogger(name, messageFactory);
                // wrap a logger from an underlying implementation
                logger = new Log4jTaglibLogger(original, name, original.getMessageFactory());
                this.loggerRegistry.putIfAbsent(name, messageFactory, logger);

        return logger;

    public boolean hasLogger(final String name) {
        return loggerRegistry.hasLogger(name);

    public boolean hasLogger(final String name, final MessageFactory messageFactory) {
        return loggerRegistry.hasLogger(name, messageFactory);

    public boolean hasLogger(final String name, final Class<? extends MessageFactory> messageFactoryClass) {
        return loggerRegistry.hasLogger(name, messageFactoryClass);

    static synchronized Log4jTaglibLoggerContext getInstance(final ServletContext servletContext) {
        Log4jTaglibLoggerContext loggerContext = CONTEXTS.get(servletContext);
        if (loggerContext != null) {
            return loggerContext;

        synchronized (CONTEXTS) {
            loggerContext = CONTEXTS.get(servletContext);
            if (loggerContext == null) {
                loggerContext = new Log4jTaglibLoggerContext(servletContext);
                CONTEXTS.put(servletContext, loggerContext);

        return loggerContext;



Or download all of them as a single archive file:

File name: log4j-taglib-2.14.1-sources.jar
File size: 33902 bytes
Release date: 2021-03-06


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