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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  
18  package org.apache.log4j;
19  
20  import org.apache.log4j.spi.OptionHandler;
21  import org.apache.log4j.spi.LoggingEvent;
22  
23  /**
24     Extend this abstract class to create your own log layout format.
25     
26     @author Ceki Gülcü
27  
28  */
29    
30  public abstract class Layout implements OptionHandler {
31  
32    // Note that the line.separator property can be looked up even by
33    // applets.
34    public final static String LINE_SEP = System.getProperty("line.separator");
35    public final static int LINE_SEP_LEN  = LINE_SEP.length();
36  
37  
38    /**
39       Implement this method to create your own layout format.
40    */
41    abstract
42    public
43    String format(LoggingEvent event);
44  
45    /**
46       Returns the content type output by this layout. The base class
47       returns "text/plain". 
48    */
49    public
50    String getContentType() {
51      return "text/plain";
52    }
53  
54    /**
55       Returns the header for the layout format. The base class returns
56       <code>null</code>.  */
57    public
58    String getHeader() {
59      return null;
60    }
61  
62    /**
63       Returns the footer for the layout format. The base class returns
64       <code>null</code>.  */
65    public
66    String getFooter() {
67      return null;
68    }
69  
70  
71  
72    /**
73       If the layout handles the throwable object contained within
74       {@link LoggingEvent}, then the layout should return
75       <code>false</code>. Otherwise, if the layout ignores throwable
76       object, then the layout should return <code>true</code>.
77       If ignoresThrowable is true, the appender is responsible for
78       rendering the throwable.
79  
80       <p>The {@link SimpleLayout}, {@link TTCCLayout}, {@link
81       PatternLayout} all return <code>true</code>. The {@link
82       org.apache.log4j.xml.XMLLayout} returns <code>false</code>.
83  
84       @since 0.8.4 */
85    abstract
86    public
87    boolean ignoresThrowable();
88  
89  }