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.log4j;
018
019import org.apache.log4j.spi.LoggingEvent;
020import org.apache.logging.log4j.core.util.Constants;
021
022/**
023 *
024 */
025public abstract class Layout {
026
027    /** Note that the line.separator property can be looked up even by applets. */
028    public static final int LINE_SEP_LEN = Constants.LINE_SEPARATOR.length();
029
030    /**
031     * Implement this method to create your own layout format.
032     * @param event The LoggingEvent.
033     * @return The formatted LoggingEvent.
034     */
035    public abstract String format(LoggingEvent event);
036
037    /**
038     * Returns the content type output by this layout. The base class
039     * returns "text/plain".
040     * @return the type of content rendered by the Layout.
041     */
042    public String getContentType() {
043        return "text/plain";
044    }
045
046    /**
047     * Returns the header for the layout format. The base class returns
048     * <code>null</code>.
049     * @return The header.
050     */
051    public String getHeader() {
052        return null;
053    }
054
055    /**
056     * Returns the footer for the layout format. The base class returns
057     * <code>null</code>.
058     * @return The footer.
059     */
060    public String getFooter() {
061        return null;
062    }
063
064
065    /**
066     * If the layout handles the throwable object contained within
067     * {@link LoggingEvent}, then the layout should return
068     * {@code false}. Otherwise, if the layout ignores throwable
069     * object, then the layout should return {@code true}.
070     * If ignoresThrowable is true, the appender is responsible for
071     * rendering the throwable.
072     * <p>
073     * The <a href="/log4j/1.2/apidocs/org/apache/log4j/SimpleLayout.html">SimpleLayout</a>,
074     * <a href="/log4j/1.2/apidocs/org/apache/log4j/TTCCLayout.html">TTCCLayout</a>,
075     * <a href="/log4j/1.2/apidocs/org/apache/log4j/PatternLayout.html">PatternLayout</a>
076     * all return {@code true}. The
077     * <a href="/log4j/1.2/apidocs/org/apache/log4j/xml/XMLLayout.html">XMLLayout</a>
078     * returns {@code false}.
079     * </p>
080     *
081     * @return true if the Layout ignores Throwables.
082     *
083     * @since 0.8.4
084     */
085    public abstract boolean ignoresThrowable();
086}
087