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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  import org.apache.logging.log4j.core.util.Constants;
21  
22  /**
23   *
24   */
25  public abstract class Layout {
26  
27      /** Note that the line.separator property can be looked up even by applets. */
28      public static final int LINE_SEP_LEN = Constants.LINE_SEPARATOR.length();
29  
30      /**
31       * Implement this method to create your own layout format.
32       * @param event The LoggingEvent.
33       * @return The formatted LoggingEvent.
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       * @return the type of content rendered by the Layout.
41       */
42      public String getContentType() {
43          return "text/plain";
44      }
45  
46      /**
47       * Returns the header for the layout format. The base class returns
48       * <code>null</code>.
49       * @return The header.
50       */
51      public String getHeader() {
52          return null;
53      }
54  
55      /**
56       * Returns the footer for the layout format. The base class returns
57       * <code>null</code>.
58       * @return The footer.
59       */
60      public String getFooter() {
61          return null;
62      }
63  
64  
65      /**
66       * If the layout handles the throwable object contained within
67       * {@link LoggingEvent}, then the layout should return
68       * {@code false}. Otherwise, if the layout ignores throwable
69       * object, then the layout should return {@code true}.
70       * If ignoresThrowable is true, the appender is responsible for
71       * rendering the throwable.
72       * <p/>
73       * <p>The {@link SimpleLayout}, {@link TTCCLayout}, {@link
74       * PatternLayout} all return {@code true}. The {@link
75       * org.apache.log4j.xml.XMLLayout} returns {@code false}.
76       * @return true if the Layout ignores Throwables.
77       *
78       * @since 0.8.4
79       */
80      public abstract boolean ignoresThrowable();
81  }
82