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/config/AppenderControlArraySet.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.config;

import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.atomic.AtomicReference;

import org.apache.logging.log4j.core.Appender;
import org.apache.logging.log4j.util.PerformanceSensitive;

/**
 * Data structure with similar semantics to CopyOnWriteArraySet, but giving direct access to the underlying array.
 *
 * @since 2.6
 */
@PerformanceSensitive
public class AppenderControlArraySet {
    private final AtomicReference<AppenderControl[]> appenderArray = new AtomicReference<>(new AppenderControl[0]);

    /**
     * Adds an AppenderControl to this set. If this set already contains the element, the call leaves the set unchanged
     * and returns false.
     *
     * @param control The AppenderControl to add.
     * @return true if this set did not already contain the specified element
     */
    public boolean add(final AppenderControl control) {
        boolean success;
        do {
            final AppenderControl[] original = appenderArray.get();
            for (final AppenderControl existing : original) {
                if (existing.equals(control)) {
                    return false; // the appender is already in the list
                }
            }
            final AppenderControl[] copy = Arrays.copyOf(original, original.length + 1);
            copy[copy.length - 1] = control;
            success = appenderArray.compareAndSet(original, copy);
        } while (!success); // could not swap: array was modified by another thread
        return true; // successfully added
    }

    /**
     * Removes the AppenderControl with the specific name and returns it (or {@code null} if no such appender existed).
     *
     * @param name The name of the AppenderControl to remove
     * @return the removed AppenderControl or {@code null}
     */
    public AppenderControl remove(final String name) {
        boolean success;
        do {
            success = true;
            final AppenderControl[] original = appenderArray.get();
            for (int i = 0; i < original.length; i++) {
                final AppenderControl appenderControl = original[i];
                if (Objects.equals(name, appenderControl.getAppenderName())) {
                    final AppenderControl[] copy = removeElementAt(i, original);
                    if (appenderArray.compareAndSet(original, copy)) {
                        return appenderControl; // successfully removed
                    }
                    success = false; // could not swap: array was modified by another thread
                    break;
                }
            }
        } while (!success);
        return null; // not found
    }

    private AppenderControl[] removeElementAt(final int i, final AppenderControl[] array) {
        final AppenderControl[] result = Arrays.copyOf(array, array.length - 1);
        System.arraycopy(array, i + 1, result, i, result.length - i);
        return result;
    }

    /**
     * Returns all Appenders as a Map.
     *
     * @return a Map with the Appender name as the key and the Appender as the value.
     */
    public Map<String, Appender> asMap() {
        final Map<String, Appender> result = new HashMap<>();
        for (final AppenderControl appenderControl : appenderArray.get()) {
            result.put(appenderControl.getAppenderName(), appenderControl.getAppender());
        }
        return result;
    }

    /**
     * Atomically sets the values to an empty array and returns the old array.
     *
     * @return the contents before this collection was cleared.
     */
    public AppenderControl[] clear() {
        return appenderArray.getAndSet(new AppenderControl[0]);
    }

    public boolean isEmpty() {
        return appenderArray.get().length == 0;
    }

    /**
     * Returns the underlying array.
     *
     * @return the array supporting this collection
     */
    public AppenderControl[] get() {
        return appenderArray.get();
    }

    @Override
    public String toString() {
        return "AppenderControlArraySet [appenderArray=" + appenderArray + "]";
    }
}

⏎ org/apache/logging/log4j/core/config/AppenderControlArraySet.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
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