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.log4j;
018    
019    import org.apache.log4j.spi.LoggingEvent;
020    import org.apache.logging.log4j.core.util.Constants;
021    
022    /**
023     *
024     */
025    public 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