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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 org.apache.logging.log4j.core.LogEvent;
20  
21  /**
22   * LoggingEventPatternConverter is a base class for pattern converters
23   * that can format information from instances of LoggingEvent.
24   */
25  public abstract class LogEventPatternConverter extends AbstractPatternConverter {
26  
27      /**
28       * Constructs an instance of LoggingEventPatternConverter.
29       *
30       * @param name  name of converter.
31       * @param style CSS style for output.
32       */
33      protected LogEventPatternConverter(final String name, final String style) {
34          super(name, style);
35      }
36  
37      /**
38       * Formats an event into a string buffer.
39       *
40       * @param event      event to format, may not be null.
41       * @param toAppendTo string buffer to which the formatted event will be appended.  May not be null.
42       */
43      public abstract void format(final LogEvent event, final StringBuilder toAppendTo);
44  
45      /**
46       * {@inheritDoc}
47       */
48      @Override
49      public void format(final Object obj, final StringBuilder output) {
50          if (obj instanceof LogEvent) {
51              format((LogEvent) obj, output);
52          }
53      }
54  
55      /**
56       * Normally pattern converters are not meant to handle Exceptions although
57       * few pattern converters might.
58       * <p/>
59       * By examining the return values for this method, the containing layout will
60       * determine whether it handles throwables or not.
61       *
62       * @return true if this PatternConverter handles throwables
63       */
64      public boolean handlesThrowable() {
65          return false;
66      }
67  }