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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.spi;
19  
20  import org.apache.log4j.*;
21  import org.apache.log4j.helpers.LogLog;
22  
23  
24  // Contibutors: Mathias Bogaert
25  
26  /***
27     RootLogger sits at the top of the logger hierachy. It is a
28     regular logger except that it provides several guarantees.
29  
30     <p>First, it cannot be assigned a <code>null</code>
31     level. Second, since root logger cannot have a parent, the
32     {@link #getChainedLevel} method always returns the value of the
33     level field without walking the hierarchy.
34  
35     @author Ceki G&uuml;lc&uuml;
36  
37   */
38  public final class RootLogger extends Logger {
39    /***
40       The root logger names itself as "root". However, the root
41       logger cannot be retrieved by name.
42    */
43    public RootLogger(Level level) {
44      super("root");
45      setLevel(level);
46    }
47  
48    /***
49       Return the assigned level value without walking the logger
50       hierarchy.
51    */
52    public final Level getChainedLevel() {
53      return level;
54    }
55  
56    /***
57       Setting a null value to the level of the root logger may have catastrophic
58       results. We prevent this here.
59  
60       @since 0.8.3 */
61    public final void setLevel(Level level) {
62      if (level == null) {
63        LogLog.error(
64          "You have tried to set a null level to root.", new Throwable());
65      } else {
66        this.level = level;
67      }
68    }
69  
70  }