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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