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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements. See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache license, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License. You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the license for the specific language governing permissions and
15   * limitations under the license.
16   */
17  package org.apache.logging.log4j.core.pattern;
18  
19  import java.util.concurrent.atomic.AtomicLong;
20  
21  import org.apache.logging.log4j.core.LogEvent;
22  import org.apache.logging.log4j.core.config.plugins.Plugin;
23  
24  /**
25   * Formats the event sequence number.
26   */
27  @Plugin(name = "SequenceNumberPatternConverter", category = "Converter")
28  @ConverterKeys({ "sn", "sequenceNumber" })
29  public final class SequenceNumberPatternConverter extends LogEventPatternConverter {
30  
31      private static final AtomicLong SEQUENCE = new AtomicLong();
32  
33      /**
34       * Singleton.
35       */
36      private static final SequenceNumberPatternConverter INSTANCE =
37          new SequenceNumberPatternConverter();
38  
39      /**
40       * Private constructor.
41       */
42      private SequenceNumberPatternConverter() {
43          super("Sequence Number", "sn");
44      }
45  
46      /**
47       * Obtains an instance of SequencePatternConverter.
48       *
49       * @param options options, currently ignored, may be null.
50       * @return instance of SequencePatternConverter.
51       */
52      public static SequenceNumberPatternConverter newInstance(
53          final String[] options) {
54          return INSTANCE;
55      }
56  
57      /**
58       * {@inheritDoc}
59       */
60      @Override
61      public void format(final LogEvent event, final StringBuilder toAppendTo) {
62          toAppendTo.append(Long.toString(SEQUENCE.incrementAndGet()));
63      }
64  }