    001    /*
    002     * Licensed to the Apache Software Foundation (ASF) under one or more
    003     * contributor license agreements. See the NOTICE file distributed with
    004     * this work for additional information regarding copyright ownership.
    005     * The ASF licenses this file to You under the Apache license, Version 2.0
    006     * (the "License"); you may not use this file except in compliance with
    007     * the License. You may obtain a copy of the License at
    008     *
    009     *      http://www.apache.org/licenses/LICENSE-2.0
    010     *
    011     * Unless required by applicable law or agreed to in writing, software
    012     * distributed under the License is distributed on an "AS IS" BASIS,
    013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014     * See the license for the specific language governing permissions and
    015     * limitations under the license.
    016     */
    017    package org.apache.logging.log4j.core.pattern;
    018
    019    import java.util.concurrent.atomic.AtomicLong;
    020
    021    import org.apache.logging.log4j.core.LogEvent;
    022    import org.apache.logging.log4j.core.config.plugins.Plugin;
    023
    024
    025    /**
    026     * Formats the event sequence number.
    027     */
    028    @Plugin(name = "SequenceNumberPatternConverter", category = "Converter")
    029    @ConverterKeys({ "sn", "sequenceNumber" })
    030    public final class SequenceNumberPatternConverter extends LogEventPatternConverter {
    031
    032        private static final AtomicLong SEQUENCE = new AtomicLong();
    033
    034        /**
    035         * Singleton.
    036         */
    037        private static final SequenceNumberPatternConverter INSTANCE =
    038            new SequenceNumberPatternConverter();
    039
    040        /**
    041         * Private constructor.
    042         */
    043        private SequenceNumberPatternConverter() {
    044            super("Sequence Number", "sn");
    045        }
    046
    047        /**
    048         * Obtains an instance of SequencePatternConverter.
    049         *
    050         * @param options options, currently ignored, may be null.
    051         * @return instance of SequencePatternConverter.
    052         */
    053        public static SequenceNumberPatternConverter newInstance(
    054            final String[] options) {
    055            return INSTANCE;
    056        }
    057
    058        /**
    059         * {@inheritDoc}
    060         */
    061        @Override
    062        public void format(final LogEvent event, final StringBuilder toAppendTo) {
    063            toAppendTo.append(Long.toString(SEQUENCE.incrementAndGet()));
    064        }
    065    }