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/impl/ContextDataFactory.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.impl;

import java.lang.reflect.Constructor;
import java.util.Map;
import java.util.Map.Entry;

import org.apache.logging.log4j.core.ContextDataInjector;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.util.Loader;
import org.apache.logging.log4j.util.IndexedStringMap;
import org.apache.logging.log4j.util.PropertiesUtil;
import org.apache.logging.log4j.util.ReadOnlyStringMap;
import org.apache.logging.log4j.util.SortedArrayStringMap;
import org.apache.logging.log4j.util.StringMap;

/**
 * Factory for creating the StringMap instances used to initialize LogEvents' {@linkplain LogEvent#getContextData()
 * context data}. When context data is {@linkplain ContextDataInjector injected} into the log event, these StringMap
 * instances may be either populated with key-value pairs from the context, or completely replaced altogether.
 * <p>
 * By default returns {@code SortedArrayStringMap} objects. Can be configured by setting system property
 * {@code "log4j2.ContextData"} to the fully qualified class name of a class implementing the {@code StringMap}
 * interface. The class must have a public default constructor, and if possible should also have a public constructor
 * that takes a single {@code int} argument for the initial capacity.
 * </p>
 *
 * @see LogEvent#getContextData()
 * @see ContextDataInjector
 * @see SortedArrayStringMap
 * @since 2.7
 */
public class ContextDataFactory {
    private static final String CLASS_NAME = PropertiesUtil.getProperties().getStringProperty("log4j2.ContextData");
    private static final Class<? extends StringMap> CACHED_CLASS = createCachedClass(CLASS_NAME);

    /**
     * In LOG4J2-2649 (https://issues.apache.org/jira/browse/LOG4J2-2649),
     * the reporter said some reason about using graalvm to static compile.
     * In graalvm doc (https://github.com/oracle/graal/blob/master/substratevm/LIMITATIONS.md),
     * graalvm is not support MethodHandle now, so the Constructor need not to return MethodHandle.
     */
    private static final Constructor<?> DEFAULT_CONSTRUCTOR = createDefaultConstructor(CACHED_CLASS);
    private static final Constructor<?> INITIAL_CAPACITY_CONSTRUCTOR = createInitialCapacityConstructor(CACHED_CLASS);

    private static final StringMap EMPTY_STRING_MAP = createContextData(0);

    static {
        EMPTY_STRING_MAP.freeze();
    }

    private static Class<? extends StringMap> createCachedClass(final String className) {
        if (className == null) {
            return null;
        }
        try {
            return Loader.loadClass(className).asSubclass(IndexedStringMap.class);
        } catch (final Exception any) {
            return null;
        }
    }

    private static Constructor<?> createDefaultConstructor(final Class<? extends StringMap> cachedClass){
        if (cachedClass == null) {
            return null;
        }
        try {
            return cachedClass.getConstructor();
        } catch (final NoSuchMethodException | IllegalAccessError ignored) {
            return null;
        }
    }

    private static Constructor<?> createInitialCapacityConstructor(final Class<? extends StringMap> cachedClass){
        if (cachedClass == null) {
            return null;
        }
        try {
            return cachedClass.getConstructor(int.class);
        } catch (final NoSuchMethodException | IllegalAccessError ignored) {
            return null;
        }
    }

    public static StringMap createContextData() {
        if (DEFAULT_CONSTRUCTOR == null) {
            return new SortedArrayStringMap();
        }
        try {
            return (IndexedStringMap) DEFAULT_CONSTRUCTOR.newInstance();
        } catch (final Throwable ignored) {
            return new SortedArrayStringMap();
        }
    }

    public static StringMap createContextData(final int initialCapacity) {
        if (INITIAL_CAPACITY_CONSTRUCTOR == null) {
            return new SortedArrayStringMap(initialCapacity);
        }
        try {
            return (IndexedStringMap) INITIAL_CAPACITY_CONSTRUCTOR.newInstance(initialCapacity);
        } catch (final Throwable ignored) {
            return new SortedArrayStringMap(initialCapacity);
        }
    }

    public static StringMap createContextData(final Map<String, String> context) {
        final StringMap contextData = createContextData(context.size());
        for (final Entry<String, String> entry : context.entrySet()) {
            contextData.putValue(entry.getKey(), entry.getValue());
        }
        return contextData;
    }

    public static StringMap createContextData(final ReadOnlyStringMap readOnlyStringMap) {
        final StringMap contextData = createContextData(readOnlyStringMap.size());
        contextData.putAll(readOnlyStringMap);
        return contextData;
    }

    /**
     * An empty pre-frozen IndexedStringMap. The returned object may be shared.
     *
     * @return an empty pre-frozen IndexedStringMap
     */
    public static StringMap emptyFrozenContextData() {
        return EMPTY_STRING_MAP;
    }

}

⏎ org/apache/logging/log4j/core/impl/ContextDataFactory.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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