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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       * The <a href="/log4j/1.2/apidocs/org/apache/log4j/SimpleLayout.html">SimpleLayout</a>,
    74       * <a href="/log4j/1.2/apidocs/org/apache/log4j/TTCCLayout.html">TTCCLayout</a>,
    75       * <a href="/log4j/1.2/apidocs/org/apache/log4j/PatternLayout.html">PatternLayout</a>
    76       * all return {@code true}. The
    77       * <a href="/log4j/1.2/apidocs/org/apache/log4j/xml/XMLLayout.html">XMLLayout</a>
    78       * returns {@code false}.
    79       * </p>
    80       *
    81       * @return true if the Layout ignores Throwables.
    82       *
    83       * @since 0.8.4
    84       */
    85      public abstract boolean ignoresThrowable();
    86  }
    87