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