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.ArrayList;
import java.util.List;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.tagext.BodyTag;
import javax.servlet.jsp.tagext.DynamicAttributes;
import javax.servlet.jsp.tagext.Tag;

import org.apache.logging.log4j.Level;
import org.apache.logging.log4j.Marker;
import org.apache.logging.log4j.message.Message;

 * Implements common methods for logging tags that accept messages and markers.
 * @since 2.0
abstract class LoggingMessageTagSupport extends ExceptionAwareTagSupport implements DynamicAttributes {
    private static final long serialVersionUID = 1L;

    private static final String FQCN = LoggingMessageTagSupport.class.getName();

    private transient Object message;

    private Marker marker;

    private List<Object> attributes;

    protected void init() {
        this.message = null;
        this.marker = null;
        if (this.attributes == null) {
            this.attributes = new ArrayList<>();
        } else {

    protected final Object getMessage() throws JspException {
        if (this.message == null) {
            if (this.getBodyContent() == null) {
                throw new JspException("Either message attribute or body content must be specified.");
            return this.getBodyContent().getString();
        return this.message;

    public final void setMessage(final Object message) {
        this.message = message;

    protected final Marker getMarker() {
        return this.marker;

    public final void setMarker(final Marker marker) {
        this.marker = marker;

    protected abstract Level getLevel();

    public final void setDynamicAttribute(final String uri, final String name, final Object value) {

    public final int doStartTag() {
        return BodyTag.EVAL_BODY_BUFFERED;

    public final int doEndTag() throws JspException {
        final Log4jTaglibLogger logger = this.getLogger();
        final Level level = this.getLevel();
        final Marker marker = this.getMarker();

        if (TagUtils.isEnabled(logger, level, marker)) {
            final Object message = this.getMessage();
            final Throwable exception = this.getException();
            if (message instanceof Message) {
                logger.logIfEnabled(FQCN, level, marker, (Message) message, exception);
            } else if (message instanceof String) {
                Message data;
                if (this.attributes.size() > 0) {
                    data = logger.getMessageFactory().newMessage((String) message, this.attributes.toArray());
                } else {
                    data = logger.getMessageFactory().newMessage((String) message);
                logger.logIfEnabled(FQCN, level, marker, data, exception);
            } else {
                logger.logIfEnabled(FQCN, level, marker, logger.getMessageFactory().newMessage(message), exception);

        return Tag.EVAL_PAGE;



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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