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/util/datetime/FormatCache.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.util.datetime;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Locale;
import java.util.TimeZone;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

/**
 * <p>FormatCache is a cache and factory for {@link Format}s.</p>
 *
 * <p>
 * Copied and modified from <a href="https://commons.apache.org/proper/commons-lang/">Apache Commons Lang</a>.
 * </p>
 *
 * @since Apache Commons Lang 3.0
 */
// TODO: Before making public move from getDateTimeInstance(Integer,...) to int; or some other approach.
abstract class FormatCache<F extends Format> {

    /**
     * No date or no time.  Used in same parameters as DateFormat.SHORT or DateFormat.LONG
     */
    static final int NONE= -1;

    private final ConcurrentMap<MultipartKey, F> cInstanceCache
        = new ConcurrentHashMap<>(7);

    private static final ConcurrentMap<MultipartKey, String> cDateTimeInstanceCache
        = new ConcurrentHashMap<>(7);

    /**
     * <p>Gets a formatter instance using the default pattern in the
     * default timezone and locale.</p>
     *
     * @return a date/time formatter
     */
    public F getInstance() {
        return getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT, TimeZone.getDefault(), Locale.getDefault());
    }

    /**
     * <p>Gets a formatter instance using the specified pattern, time zone
     * and locale.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible
     *  pattern, non-null
     * @param timeZone  the time zone, null means use the default TimeZone
     * @param locale  the locale, null means use the default Locale
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     *  or <code>null</code>
     */
    public F getInstance(final String pattern, TimeZone timeZone, Locale locale) {
        if (pattern == null) {
            throw new NullPointerException("pattern must not be null");
        }
        if (timeZone == null) {
            timeZone = TimeZone.getDefault();
        }
        if (locale == null) {
            locale = Locale.getDefault();
        }
        final MultipartKey key = new MultipartKey(pattern, timeZone, locale);
        F format = cInstanceCache.get(key);
        if (format == null) {
            format = createInstance(pattern, timeZone, locale);
            final F previousValue= cInstanceCache.putIfAbsent(key, format);
            if (previousValue != null) {
                // another thread snuck in and did the same work
                // we should return the instance that is in ConcurrentMap
                format= previousValue;
            }
        }
        return format;
    }

    /**
     * <p>Create a format instance using the specified pattern, time zone
     * and locale.</p>
     *
     * @param pattern  {@link java.text.SimpleDateFormat} compatible pattern, this will not be null.
     * @param timeZone  time zone, this will not be null.
     * @param locale  locale, this will not be null.
     * @return a pattern based date/time formatter
     * @throws IllegalArgumentException if pattern is invalid
     *  or <code>null</code>
     */
    abstract protected F createInstance(String pattern, TimeZone timeZone, Locale locale);

    /**
     * <p>Gets a date/time formatter instance using the specified style,
     * time zone and locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT, null indicates no date in format
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT, null indicates no time in format
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date, null means use default Locale
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     */
    // This must remain private, see LANG-884
    private F getDateTimeInstance(final Integer dateStyle, final Integer timeStyle, final TimeZone timeZone, Locale locale) {
        if (locale == null) {
            locale = Locale.getDefault();
        }
        final String pattern = getPatternForStyle(dateStyle, timeStyle, locale);
        return getInstance(pattern, timeZone, locale);
    }

    /**
     * <p>Gets a date/time formatter instance using the specified style,
     * time zone and locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date, null means use default Locale
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     */
    // package protected, for access from FastDateFormat; do not make public or protected
    F getDateTimeInstance(final int dateStyle, final int timeStyle, final TimeZone timeZone, final Locale locale) {
        return getDateTimeInstance(Integer.valueOf(dateStyle), Integer.valueOf(timeStyle), timeZone, locale);
    }

    /**
     * <p>Gets a date formatter instance using the specified style,
     * time zone and locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date, null means use default Locale
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     */
    // package protected, for access from FastDateFormat; do not make public or protected
    F getDateInstance(final int dateStyle, final TimeZone timeZone, final Locale locale) {
        return getDateTimeInstance(Integer.valueOf(dateStyle), null, timeZone, locale);
    }

    /**
     * <p>Gets a time formatter instance using the specified style,
     * time zone and locale.</p>
     *
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT
     * @param timeZone  optional time zone, overrides time zone of
     *  formatted date, null means use default Locale
     * @param locale  optional locale, overrides system locale
     * @return a localized standard date/time formatter
     * @throws IllegalArgumentException if the Locale has no date/time
     *  pattern defined
     */
    // package protected, for access from FastDateFormat; do not make public or protected
    F getTimeInstance(final int timeStyle, final TimeZone timeZone, final Locale locale) {
        return getDateTimeInstance(null, Integer.valueOf(timeStyle), timeZone, locale);
    }

    /**
     * <p>Gets a date/time format for the specified styles and locale.</p>
     *
     * @param dateStyle  date style: FULL, LONG, MEDIUM, or SHORT, null indicates no date in format
     * @param timeStyle  time style: FULL, LONG, MEDIUM, or SHORT, null indicates no time in format
     * @param locale  The non-null locale of the desired format
     * @return a localized standard date/time format
     * @throws IllegalArgumentException if the Locale has no date/time pattern defined
     */
    // package protected, for access from test code; do not make public or protected
    static String getPatternForStyle(final Integer dateStyle, final Integer timeStyle, final Locale locale) {
        final MultipartKey key = new MultipartKey(dateStyle, timeStyle, locale);

        String pattern = cDateTimeInstanceCache.get(key);
        if (pattern == null) {
            try {
                DateFormat formatter;
                if (dateStyle == null) {
                    formatter = DateFormat.getTimeInstance(timeStyle.intValue(), locale);
                }
                else if (timeStyle == null) {
                    formatter = DateFormat.getDateInstance(dateStyle.intValue(), locale);
                }
                else {
                    formatter = DateFormat.getDateTimeInstance(dateStyle.intValue(), timeStyle.intValue(), locale);
                }
                pattern = ((SimpleDateFormat)formatter).toPattern();
                final String previous = cDateTimeInstanceCache.putIfAbsent(key, pattern);
                if (previous != null) {
                    // even though it doesn't matter if another thread put the pattern
                    // it's still good practice to return the String instance that is
                    // actually in the ConcurrentMap
                    pattern= previous;
                }
            } catch (final ClassCastException ex) {
                throw new IllegalArgumentException("No date time pattern for locale: " + locale);
            }
        }
        return pattern;
    }

    // ----------------------------------------------------------------------
    /**
     * <p>Helper class to hold multi-part Map keys</p>
     */
    private static class MultipartKey {
        private final Object[] keys;
        private int hashCode;

        /**
         * Constructs an instance of <code>MultipartKey</code> to hold the specified objects.
         * @param keys the set of objects that make up the key.  Each key may be null.
         */
        public MultipartKey(final Object... keys) {
            this.keys = keys;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public boolean equals(final Object obj) {
            // Eliminate the usual boilerplate because
            // this inner static class is only used in a generic ConcurrentHashMap
            // which will not compare against other Object types
            return Arrays.equals(keys, ((MultipartKey)obj).keys);
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public int hashCode() {
            if(hashCode==0) {
                int rc= 0;
                for(final Object key : keys) {
                    if(key!=null) {
                        rc= rc*7 + key.hashCode();
                    }
                }
                hashCode= rc;
            }
            return hashCode;
        }
    }

}

⏎ org/apache/logging/log4j/core/util/datetime/FormatCache.java

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File name: log4j-core-2.14.1-sources.jar
File size: 1281358 bytes
Release date: 2021-03-06
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