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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.Filter;
20  import org.apache.log4j.spi.ErrorHandler;
21  import org.apache.log4j.spi.LoggingEvent;
22  
23  /**
24   * Implement this interface for your own strategies for outputting log
25   * statements.
26   *
27   * @author Ceki Gülcü
28   */
29  public interface Appender {
30  
31      /**
32       * Add a filter to the end of the filter list.
33       * @param newFilter The filter to add.
34       *
35       * @since 0.9.0
36       */
37      void addFilter(Filter newFilter);
38  
39      /**
40       * Returns the head Filter. The Filters are organized in a linked list
41       * and so all Filters on this Appender are available through the result.
42       *
43       * @return the head Filter or null, if no Filters are present
44       * @since 1.1
45       */
46      Filter getFilter();
47  
48      /**
49       * Clear the list of filters by removing all the filters in it.
50       *
51       * @since 0.9.0
52       */
53      void clearFilters();
54  
55      /**
56       * Release any resources allocated within the appender such as file
57       * handles, network connections, etc.
58       * <p/>
59       * <p>It is a programming error to append to a closed appender.
60       *
61       * @since 0.8.4
62       */
63      void close();
64  
65      /**
66       * Log in <code>Appender</code> specific way. When appropriate,
67       * Loggers will call the <code>doAppend</code> method of appender
68       * implementations in order to log.
69       * @param event The LoggingEvent.
70       */
71      void doAppend(LoggingEvent event);
72  
73  
74      /**
75       * Get the name of this appender.
76       *
77       * @return name, may be null.
78       */
79      String getName();
80  
81  
82      /**
83       * Set the {@link ErrorHandler} for this appender.
84       * @param errorHandler The error handler.
85       *
86       * @since 0.9.0
87       */
88      void setErrorHandler(ErrorHandler errorHandler);
89  
90      /**
91       * Returns the {@link ErrorHandler} for this appender.
92       * @return The error handler.
93       *
94       * @since 1.1
95       */
96      ErrorHandler getErrorHandler();
97  
98      /**
99       * Set the {@link Layout} for this appender.
100      * @param layout The Layout.
101      *
102      * @since 0.8.1
103      */
104     void setLayout(Layout layout);
105 
106     /**
107      * Returns this appenders layout.
108      * @return the Layout.
109      *
110      * @since 1.1
111      */
112     Layout getLayout();
113 
114 
115     /**
116      * Set the name of this appender. The name is used by other
117      * components to identify this appender.
118      * @param name The appender name.
119      *
120      * @since 0.8.1
121      */
122     void setName(String name);
123 
124     /**
125      * Configurators call this method to determine if the appender
126      * requires a layout. If this method returns {@code true},
127      * meaning that layout is required, then the configurator will
128      * configure an layout using the configuration information at its
129      * disposal.  If this method returns {@code false}, meaning that
130      * a layout is not required, then layout configuration will be
131      * skipped even if there is available layout configuration
132      * information at the disposal of the configurator..
133      * <p/>
134      * <p>In the rather exceptional case, where the appender
135      * implementation admits a layout but can also work without it, then
136      * the appender should return {@code true}.
137      * @return true if a Layout is required.
138      *
139      * @since 0.8.4
140      */
141     boolean requiresLayout();
142 }
143