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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  import org.apache.logging.log4j.util.PerformanceSensitive;
24  
25  /**
26   * Formats the event sequence number.
27   */
28  @Plugin(name = "SequenceNumberPatternConverter", category = "Converter")
29  @ConverterKeys({ "sn", "sequenceNumber" })
30  @PerformanceSensitive("allocation")
31  public final class SequenceNumberPatternConverter extends LogEventPatternConverter {
32  
33      private static final AtomicLong SEQUENCE = new AtomicLong();
34  
35      /**
36       * Singleton.
37       */
38      private static final SequenceNumberPatternConverter INSTANCE =
39          new SequenceNumberPatternConverter();
40  
41      /**
42       * Private constructor.
43       */
44      private SequenceNumberPatternConverter() {
45          super("Sequence Number", "sn");
46      }
47  
48      /**
49       * Obtains an instance of SequencePatternConverter.
50       *
51       * @param options options, currently ignored, may be null.
52       * @return instance of SequencePatternConverter.
53       */
54      public static SequenceNumberPatternConverter newInstance(final String[] options) {
55          return INSTANCE;
56      }
57  
58      /**
59       * {@inheritDoc}
60       */
61      @Override
62      public void format(final LogEvent event, final StringBuilder toAppendTo) {
63          toAppendTo.append(SEQUENCE.incrementAndGet());
64      }
65  }