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 */
017package org.apache.logging.log4j.core.pattern;
018
019import 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 */
025public 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}