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/appender/WriterAppender.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.appender;

import java.io.Writer;

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.StringLayout;
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.PluginBuilderFactory;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.layout.PatternLayout;
import org.apache.logging.log4j.core.util.CloseShieldWriter;

/**
 * Appends log events to a {@link Writer}.
 */
@Plugin(name = "Writer", category = Core.CATEGORY_NAME, elementType = Appender.ELEMENT_TYPE, printObject = true)
public final class WriterAppender extends AbstractWriterAppender<WriterManager> {

    /**
     * Builds WriterAppender instances.
     */
    public static class Builder<B extends Builder<B>> extends AbstractAppender.Builder<B>
            implements org.apache.logging.log4j.core.util.Builder<WriterAppender> {

        private boolean follow = false;

        private Writer target;

        @Override
        public WriterAppender build() {
            final StringLayout layout = (StringLayout) getLayout();
            final StringLayout actualLayout = layout != null ? layout : PatternLayout.createDefaultLayout();
            return new WriterAppender(getName(), actualLayout, getFilter(), getManager(target, follow, actualLayout),
                    isIgnoreExceptions(), getPropertyArray());
        }

        public B setFollow(final boolean shouldFollow) {
            this.follow = shouldFollow;
            return asBuilder();
        }

        public B setTarget(final Writer aTarget) {
            this.target = aTarget;
            return asBuilder();
        }
    }
    /**
     * Holds data to pass to factory method.
     */
    private static class FactoryData {
        private final StringLayout layout;
        private final String name;
        private final Writer writer;

        /**
         * Builds instances.
         *
         * @param writer
         *            The OutputStream.
         * @param type
         *            The name of the target.
         * @param layout
         *            A String layout
         */
        public FactoryData(final Writer writer, final String type, final StringLayout layout) {
            this.writer = writer;
            this.name = type;
            this.layout = layout;
        }
    }

    private static class WriterManagerFactory implements ManagerFactory<WriterManager, FactoryData> {

        /**
         * Creates a WriterManager.
         *
         * @param name
         *            The name of the entity to manage.
         * @param data
         *            The data required to create the entity.
         * @return The WriterManager
         */
        @Override
        public WriterManager createManager(final String name, final FactoryData data) {
            return new WriterManager(data.writer, data.name, data.layout, true);
        }
    }

    private static WriterManagerFactory factory = new WriterManagerFactory();

    /**
     * Creates a WriterAppender.
     *
     * @param layout
     *            The layout to use or null to get the default layout.
     * @param filter
     *            The Filter or null.
     * @param target
     *            The target Writer
     * @param follow
     *            If true will follow changes to the underlying output stream.
     *            Use false as the default.
     * @param name
     *            The name of the Appender (required).
     * @param ignore
     *            If {@code "true"} (default) exceptions encountered when
     *            appending events are logged; otherwise they are propagated to
     *            the caller. Use true as the default.
     * @return The ConsoleAppender.
     */
    @PluginFactory
    public static WriterAppender createAppender(StringLayout layout, final Filter filter, final Writer target,
            final String name, final boolean follow, final boolean ignore) {
        if (name == null) {
            LOGGER.error("No name provided for WriterAppender");
            return null;
        }
        if (layout == null) {
            layout = PatternLayout.createDefaultLayout();
        }
        return new WriterAppender(name, layout, filter, getManager(target, follow, layout), ignore, null);
    }

    private static WriterManager getManager(final Writer target, final boolean follow, final StringLayout layout) {
        final Writer writer = new CloseShieldWriter(target);
        final String managerName = target.getClass().getName() + "@" + Integer.toHexString(target.hashCode()) + '.'
                + follow;
        return WriterManager.getManager(managerName, new FactoryData(writer, managerName, layout), factory);
    }

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

    private WriterAppender(final String name, final StringLayout layout, final Filter filter,
            final WriterManager manager, final boolean ignoreExceptions, final Property[] properties) {
        super(name, layout, filter, ignoreExceptions, true, properties, manager);
    }

}

⏎ org/apache/logging/log4j/core/appender/WriterAppender.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
Download 

⇒ Source Code for Apache Log4j JDK Logging Adapter

⇐ Source Code for Apache Log4j API

⇑ Downloading and Reviewing Apache Log4j Packages

⇑⇑ FAQ for Apache Log4j