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    }