/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.log4j.pattern;

import org.apache.log4j.spi.LoggingEvent;

/**
 * LoggingEventPatternConverter is a base class for pattern converters that can
 * format information from instances of LoggingEvent.
 *
 * @author Curt Arnold
 *
 */
public abstract class LoggingEventPatternConverter extends PatternConverter {
    /**
     * Constructs an instance of LoggingEventPatternConverter.
     * 
     * @param name  name of converter.
     * @param style CSS style for output.
     */
    protected LoggingEventPatternConverter(final String name, final String style) {
	super(name, style);
    }

    /**
     * Formats an event into a string buffer.
     * 
     * @param event      event to format, may not be null.
     * @param toAppendTo string buffer to which the formatted event will be
     *                   appended. May not be null.
     */
    public abstract void format(final LoggingEvent event, final StringBuffer toAppendTo);

    /**
     * {@inheritDoc}
     */
    public void format(final Object obj, final StringBuffer output) {
	if (obj instanceof LoggingEvent) {
	    format((LoggingEvent) obj, output);
	}
    }

    /**
     * Normally pattern converters are not meant to handle Exceptions although few
     * pattern converters might.
     *
     * By examining the return values for this method, the containing layout will
     * determine whether it handles throwables or not.
     * 
     * @return true if this PatternConverter handles throwables
     */
    public boolean handlesThrowable() {
	return false;
    }
}
