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.ErrorHandler; 020 import org.apache.log4j.spi.Filter; 021 import org.apache.log4j.spi.LoggingEvent; 022 023 /** 024 * Implement this interface for your own strategies for outputting log 025 * statements. 026 */ 027 public interface Appender { 028 029 /** 030 * Add a filter to the end of the filter list. 031 * @param newFilter The filter to add. 032 * 033 * @since 0.9.0 034 */ 035 void addFilter(Filter newFilter); 036 037 /** 038 * Returns the head Filter. The Filters are organized in a linked list 039 * and so all Filters on this Appender are available through the result. 040 * 041 * @return the head Filter or null, if no Filters are present 042 * @since 1.1 043 */ 044 Filter getFilter(); 045 046 /** 047 * Clear the list of filters by removing all the filters in it. 048 * 049 * @since 0.9.0 050 */ 051 void clearFilters(); 052 053 /** 054 * Release any resources allocated within the appender such as file 055 * handles, network connections, etc. 056 * <p/> 057 * <p>It is a programming error to append to a closed appender. 058 * 059 * @since 0.8.4 060 */ 061 void close(); 062 063 /** 064 * Log in <code>Appender</code> specific way. When appropriate, 065 * Loggers will call the <code>doAppend</code> method of appender 066 * implementations in order to log. 067 * @param event The LoggingEvent. 068 */ 069 void doAppend(LoggingEvent event); 070 071 072 /** 073 * Get the name of this appender. 074 * 075 * @return name, may be null. 076 */ 077 String getName(); 078 079 080 /** 081 * Set the {@link ErrorHandler} for this appender. 082 * @param errorHandler The error handler. 083 * 084 * @since 0.9.0 085 */ 086 void setErrorHandler(ErrorHandler errorHandler); 087 088 /** 089 * Returns the {@link ErrorHandler} for this appender. 090 * @return The error handler. 091 * 092 * @since 1.1 093 */ 094 ErrorHandler getErrorHandler(); 095 096 /** 097 * Set the {@link Layout} for this appender. 098 * @param layout The Layout. 099 * 100 * @since 0.8.1 101 */ 102 void setLayout(Layout layout); 103 104 /** 105 * Returns this appenders layout. 106 * @return the Layout. 107 * 108 * @since 1.1 109 */ 110 Layout getLayout(); 111 112 113 /** 114 * Set the name of this appender. The name is used by other 115 * components to identify this appender. 116 * @param name The appender name. 117 * 118 * @since 0.8.1 119 */ 120 void setName(String name); 121 122 /** 123 * Configurators call this method to determine if the appender 124 * requires a layout. If this method returns {@code true}, 125 * meaning that layout is required, then the configurator will 126 * configure an layout using the configuration information at its 127 * disposal. If this method returns {@code false}, meaning that 128 * a layout is not required, then layout configuration will be 129 * skipped even if there is available layout configuration 130 * information at the disposal of the configurator.. 131 * <p/> 132 * <p>In the rather exceptional case, where the appender 133 * implementation admits a layout but can also work without it, then 134 * the appender should return {@code true}. 135 * @return true if a Layout is required. 136 * 137 * @since 0.8.4 138 */ 139 boolean requiresLayout(); 140 } 141