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