Source Code for Apache Log4j Core Implementation

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 and source package like You can download them at Apache Log4j Website.

You can also browse Source Code files for Apache Log4j Core Implementation 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.core.appender;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.core.Core;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.config.Configuration;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginBuilderAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginBuilderFactory;
import org.apache.logging.log4j.core.config.plugins.validation.constraints.Required;
import org.apache.logging.log4j.core.util.Booleans;
import org.apache.logging.log4j.core.util.Integers;

 * File Appender.
@Plugin(name = FileAppender.PLUGIN_NAME, category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE, printObject = true)
public final class FileAppender extends AbstractOutputStreamAppender<FileManager> {

    public static final String PLUGIN_NAME = "File";

     * Builds FileAppender instances.
     * @param <B>
     *            The type to build
    public static class Builder<B extends Builder<B>> extends AbstractOutputStreamAppender.Builder<B>
            implements org.apache.logging.log4j.core.util.Builder<FileAppender> {

        private String fileName;

        private boolean append = true;

        private boolean locking;

        private boolean advertise;

        private String advertiseUri;

        private boolean createOnDemand;

        private String filePermissions;

        private String fileOwner;

        private String fileGroup;

        public FileAppender build() {
            boolean bufferedIo = isBufferedIo();
            final int bufferSize = getBufferSize();
            if (locking && bufferedIo) {
                LOGGER.warn("Locking and buffering are mutually exclusive. No buffering will occur for {}", fileName);
                bufferedIo = false;
            if (!bufferedIo && bufferSize > 0) {
                LOGGER.warn("The bufferSize is set to {} but bufferedIo is false: {}", bufferSize, bufferedIo);
            final Layout<? extends Serializable> layout = getOrCreateLayout();

            final FileManager manager = FileManager.getFileManager(fileName, append, locking, bufferedIo, createOnDemand,
                    advertiseUri, layout, bufferSize, filePermissions, fileOwner, fileGroup, getConfiguration());
            if (manager == null) {
                return null;

            return new FileAppender(getName(), layout, getFilter(), manager, fileName, isIgnoreExceptions(),
                    !bufferedIo || isImmediateFlush(), advertise ? getConfiguration().getAdvertiser() : null,

        public String getAdvertiseUri() {
            return advertiseUri;

        public String getFileName() {
            return fileName;

        public boolean isAdvertise() {
            return advertise;

        public boolean isAppend() {
            return append;

        public boolean isCreateOnDemand() {
            return createOnDemand;

        public boolean isLocking() {
            return locking;

        public String getFilePermissions() {
            return filePermissions;

        public String getFileOwner() {
            return fileOwner;

        public String getFileGroup() {
            return fileGroup;

        public B withAdvertise(final boolean advertise) {
            this.advertise = advertise;
            return asBuilder();

        public B withAdvertiseUri(final String advertiseUri) {
            this.advertiseUri = advertiseUri;
            return asBuilder();

        public B withAppend(final boolean append) {
            this.append = append;
            return asBuilder();

        public B withFileName(final String fileName) {
            this.fileName = fileName;
            return asBuilder();

        public B withCreateOnDemand(final boolean createOnDemand) {
            this.createOnDemand = createOnDemand;
            return asBuilder();

        public B withLocking(final boolean locking) {
            this.locking = locking;
            return asBuilder();

        public B withFilePermissions(final String filePermissions) {
            this.filePermissions = filePermissions;
            return asBuilder();

        public B withFileOwner(final String fileOwner) {
            this.fileOwner = fileOwner;
            return asBuilder();

        public B withFileGroup(final String fileGroup) {
            this.fileGroup = fileGroup;
            return asBuilder();


    private static final int DEFAULT_BUFFER_SIZE = 8192;

     * Create a File Appender.
     * @param fileName The name and path of the file.
     * @param append "True" if the file should be appended to, "false" if it should be overwritten.
     * The default is "true".
     * @param locking "True" if the file should be locked. The default is "false".
     * @param name The name of the Appender.
     * @param immediateFlush "true" if the contents should be flushed on every write, "false" otherwise. The default
     * is "true".
     * @param ignoreExceptions If {@code "true"} (default) exceptions encountered when appending events are logged; otherwise
     *               they are propagated to the caller.
     * @param bufferedIo "true" if I/O should be buffered, "false" otherwise. The default is "true".
     * @param bufferSizeStr buffer size for buffered IO (default is 8192).
     * @param layout The layout to use to format the event. If no layout is provided the default PatternLayout
     * will be used.
     * @param filter The filter, if any, to use.
     * @param advertise "true" if the appender configuration should be advertised, "false" otherwise.
     * @param advertiseUri The advertised URI which can be used to retrieve the file contents.
     * @param config The Configuration
     * @return The FileAppender.
     * @deprecated Use {@link #newBuilder()}
    public static <B extends Builder<B>> FileAppender createAppender(
            // @formatter:off
            final String fileName,
            final String append,
            final String locking,
            final String name,
            final String immediateFlush,
            final String ignoreExceptions,
            final String bufferedIo,
            final String bufferSizeStr,
            final Layout<? extends Serializable> layout,
            final Filter filter,
            final String advertise,
            final String advertiseUri,
            final Configuration config) {
        return FileAppender.<B>newBuilder()
        .withAppend(Booleans.parseBoolean(append, true))
        .withBufferedIo(Booleans.parseBoolean(bufferedIo, true))
        .withBufferSize(Integers.parseInt(bufferSizeStr, DEFAULT_BUFFER_SIZE))
        .withFileName(fileName).setFilter(filter).setIgnoreExceptions(Booleans.parseBoolean(ignoreExceptions, true))
            .withImmediateFlush(Booleans.parseBoolean(immediateFlush, true)).setLayout(layout)
        // @formatter:on

    public static <B extends Builder<B>> B newBuilder() {
        return new Builder<B>().asBuilder();

    private final String fileName;

    private final Advertiser advertiser;

    private final Object advertisement;

    private FileAppender(final String name, final Layout<? extends Serializable> layout, final Filter filter,
            final FileManager manager, final String filename, final boolean ignoreExceptions,
            final boolean immediateFlush, final Advertiser advertiser, final Property[] properties) {

        super(name, layout, filter, ignoreExceptions, immediateFlush, properties, manager);
        if (advertiser != null) {
            final Map<String, String> configuration = new HashMap<>(layout.getContentFormat());
            configuration.put("contentType", layout.getContentType());
            configuration.put("name", name);
            advertisement = advertiser.advertise(configuration);
        } else {
            advertisement = null;
        this.fileName = filename;
        this.advertiser = advertiser;

     * Returns the file name this appender is associated with.
     * @return The File name.
    public String getFileName() {
        return this.fileName;

    public boolean stop(final long timeout, final TimeUnit timeUnit) {
        super.stop(timeout, timeUnit, false);
        if (advertiser != null) {
        return true;



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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