1   /**
2    * Distribution License:
3    * JSword is free software; you can redistribute it and/or modify it under
4    * the terms of the GNU Lesser General Public License, version 2.1 or later
5    * as published by the Free Software Foundation. This program is distributed
6    * in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
7    * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
8    * See the GNU Lesser General Public License for more details.
9    *
10   * The License is available on the internet at:
11   *      http://www.gnu.org/copyleft/lgpl.html
12   * or by writing to:
13   *      Free Software Foundation, Inc.
14   *      59 Temple Place - Suite 330
15   *      Boston, MA 02111-1307, USA
16   *
17   * © CrossWire Bible Society, 2005 - 2016
18   *
19   */
20  package org.crosswire.common.util;
21  
22  
23  /**
24   * This singleton class provides a way for a method to determine which class
25   * called it.
26   * <p>
27   * It has been tested to work in command line and WebStart environments.
28   * 
29   * @see gnu.lgpl.License The GNU Lesser General Public License for details.
30   * @author DM Smith
31   */
32  public final class CallContext {
33      /**
34       * Prevent instantiation
35       */
36      private CallContext() {
37      }
38  
39      /**
40       * Singleton accessor
41       * 
42       * @return this singleton
43       */
44      public static CallContext instance() {
45          return resolver;
46      }
47  
48      /**
49       * When called from a method it will return the class calling that method.
50       * 
51       * @return the immediate calling class
52       */
53      public static Class<?> getCallingClass() {
54          return getCallingClass(1); // add 1 for this method
55      }
56  
57      /**
58       * When called from a method it will return the i-th class calling that
59       * method, up the call chain. If used with a -1 it will return the class
60       * making the call -2 and -3 will return this class
61       * 
62       * @param i the i-th coller
63       * @return the desired calling class
64       * @throws ArrayIndexOutOfBoundsException
65       *             if the index is not valid
66       */
67      public static Class<?> getCallingClass(int i) {
68          try {
69              return Class.forName(Thread.currentThread().getStackTrace()[CALL_CONTEXT_OFFSET + i].getClassName());
70          } catch (ClassNotFoundException e) {
71              return CallContext.class;
72          }
73      }
74  
75      // may need to change if this class is redesigned
76      /**
77       * Offset needed to represent the caller of the method that called this
78       * method.
79       * 
80       */
81      private static final int CALL_CONTEXT_OFFSET = 3;
82  
83      private static CallContext resolver = new CallContext();
84  }
85