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     */
017    package org.apache.logging.log4j.core.pattern;
018    
019    import org.apache.logging.log4j.core.LogEvent;
020    
021    /**
022     * LoggingEventPatternConverter is a base class for pattern converters
023     * that can format information from instances of LoggingEvent.
024     */
025    public abstract class LogEventPatternConverter extends AbstractPatternConverter {
026    
027        /**
028         * Constructs an instance of LoggingEventPatternConverter.
029         *
030         * @param name  name of converter.
031         * @param style CSS style for output.
032         */
033        protected LogEventPatternConverter(final String name, final String style) {
034            super(name, style);
035        }
036    
037        /**
038         * Formats an event into a string buffer.
039         *
040         * @param event      event to format, may not be null.
041         * @param toAppendTo string buffer to which the formatted event will be appended.  May not be null.
042         */
043        public abstract void format(final LogEvent event, final StringBuilder toAppendTo);
044    
045        /**
046         * {@inheritDoc}
047         */
048        @Override
049        public void format(final Object obj, final StringBuilder output) {
050            if (obj instanceof LogEvent) {
051                format((LogEvent) obj, output);
052            }
053        }
054    
055        /**
056         * Normally pattern converters are not meant to handle Exceptions although few pattern converters might.
057         * <p>
058         * By examining the return values for this method, the containing layout will determine whether it handles
059         * throwables or not.
060         * </p>
061         *
062         * @return true if this PatternConverter handles throwables
063         */
064        public boolean handlesThrowable() {
065            return false;
066        }
067    }