1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache license, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the license for the specific language governing permissions and 15 * limitations under the license. 16 */ 17 package org.apache.log4j; 18 19 import org.apache.log4j.spi.ErrorHandler; 20 import org.apache.log4j.spi.Filter; 21 import org.apache.log4j.spi.LoggingEvent; 22 23 /** 24 * Implement this interface for your own strategies for outputting log 25 * statements. 26 */ 27 public interface Appender { 28 29 /** 30 * Add a filter to the end of the filter list. 31 * @param newFilter The filter to add. 32 * 33 * @since 0.9.0 34 */ 35 void addFilter(Filter newFilter); 36 37 /** 38 * Returns the head Filter. The Filters are organized in a linked list 39 * and so all Filters on this Appender are available through the result. 40 * 41 * @return the head Filter or null, if no Filters are present 42 * @since 1.1 43 */ 44 Filter getFilter(); 45 46 /** 47 * Clear the list of filters by removing all the filters in it. 48 * 49 * @since 0.9.0 50 */ 51 void clearFilters(); 52 53 /** 54 * Release any resources allocated within the appender such as file 55 * handles, network connections, etc. 56 * <p/> 57 * <p>It is a programming error to append to a closed appender. 58 * 59 * @since 0.8.4 60 */ 61 void close(); 62 63 /** 64 * Log in <code>Appender</code> specific way. When appropriate, 65 * Loggers will call the <code>doAppend</code> method of appender 66 * implementations in order to log. 67 * @param event The LoggingEvent. 68 */ 69 void doAppend(LoggingEvent event); 70 71 72 /** 73 * Get the name of this appender. 74 * 75 * @return name, may be null. 76 */ 77 String getName(); 78 79 80 /** 81 * Set the {@link ErrorHandler} for this appender. 82 * @param errorHandler The error handler. 83 * 84 * @since 0.9.0 85 */ 86 void setErrorHandler(ErrorHandler errorHandler); 87 88 /** 89 * Returns the {@link ErrorHandler} for this appender. 90 * @return The error handler. 91 * 92 * @since 1.1 93 */ 94 ErrorHandler getErrorHandler(); 95 96 /** 97 * Set the {@link Layout} for this appender. 98 * @param layout The Layout. 99 * 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