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 */
017package org.apache.logging.log4j.core.pattern;
018
019import java.util.concurrent.atomic.AtomicLong;
020
021import org.apache.logging.log4j.core.LogEvent;
022import org.apache.logging.log4j.core.config.plugins.Plugin;
023import org.apache.logging.log4j.util.PerformanceSensitive;
024
025/**
026 * Formats the event sequence number.
027 */
028@Plugin(name = "SequenceNumberPatternConverter", category = "Converter")
029@ConverterKeys({ "sn", "sequenceNumber" })
030@PerformanceSensitive("allocation")
031public final class SequenceNumberPatternConverter extends LogEventPatternConverter {
032
033    private static final AtomicLong SEQUENCE = new AtomicLong();
034
035    /**
036     * Singleton.
037     */
038    private static final SequenceNumberPatternConverter INSTANCE =
039        new SequenceNumberPatternConverter();
040
041    /**
042     * Private constructor.
043     */
044    private SequenceNumberPatternConverter() {
045        super("Sequence Number", "sn");
046    }
047
048    /**
049     * Obtains an instance of SequencePatternConverter.
050     *
051     * @param options options, currently ignored, may be null.
052     * @return instance of SequencePatternConverter.
053     */
054    public static SequenceNumberPatternConverter newInstance(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(SEQUENCE.incrementAndGet());
064    }
065}