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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 few pattern converters might.
    57       * <p>
    58       * By examining the return values for this method, the containing layout will determine whether it handles
    59       * throwables or not.
    60       * </p>
    61       *
    62       * @return true if this PatternConverter handles throwables
    63       */
    64      public boolean handlesThrowable() {
    65          return false;
    66      }
    67  }