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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.logging.log4j;
18  
19  import java.io.Serializable;
20  
21  /**
22   *  Markers are objects that are used to add easily filterable information to log messages.
23   *
24   *  Markers can be hierarchical - each Marker may have a parent. This allows for broad categories
25   *  being subdivided into more specific categories. An example might be a Marker named "Error" with
26   *  children named "SystemError" and "ApplicationError".
27   */
28  public interface Marker extends Serializable {
29  
30      /**
31       * Returns the name of this Marker.
32       * @return The name of the Marker.
33       */
34      String getName();
35  
36      /**
37       * Returns a list of parents of this Marker.
38       * @return The parent Markers or {@code null} if this Marker has no parents.
39       */
40      Marker[] getParents();
41  
42      /**
43       * Indicates whether this Marker has references to any other Markers.
44       * @return {@code true} if the Marker has parent Markers
45       */
46      boolean hasParents();
47  
48      /**
49       * Checks whether this Marker is an instance of the specified Marker.
50       * @param m The Marker to check.
51       * @return {@code true} if this Marker or one of its ancestors is the specified Marker, {@code false} otherwise.
52       * @throws IllegalArgumentException if the argument is {@code null}
53       */
54      boolean isInstanceOf(Marker m);
55  
56      /**
57       * Checks whether this Marker is an instance of the specified Marker.
58       * @param name The name of the Marker.
59       * @return {@code true} if this Marker or one of its ancestors matches the specified name, {@code false} otherwise.
60       * @throws IllegalArgumentException if the argument is {@code null}
61       */
62      boolean isInstanceOf(String name);
63  
64      /**
65       * Adds a Marker as a parent to this Marker.
66       * @param markers The parent markers to add.
67       * @return The current Marker object, thus allowing multiple adds to be concatenated.
68       * @throws IllegalArgumentException if the argument is {@code null}
69       */
70      Marker addParents(Marker... markers);
71  
72      /**
73       * Replaces the set of parent Markers with the provided Markers.
74       * @param markers The new set of parent Markers or {@code null} to clear the parents.
75       * @return The current Marker object.
76       */
77      Marker setParents(Marker... markers);
78  
79      /**
80       * Removes the specified Marker as a parent of this Marker.
81       * @param marker The marker to remove.
82       * @return {@code true} if the marker was removed.
83       * @throws IllegalArgumentException if the argument is {@code null}
84       */
85      boolean remove(Marker marker);
86  }