XPointerException


1   /* Copyright 2003, 2004 Elliotte Rusty Harold
2      
3      This library is free software; you can redistribute it and/or modify
4      it under the terms of version 2.1 of the GNU Lesser General Public 
5      License as published by the Free Software Foundation.
6      
7      This library is distributed in the hope that it will be useful,
8      but WITHOUT ANY WARRANTY; without even the implied warranty of
9      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
10     GNU Lesser General Public License for more details.
11     
12     You should have received a copy of the GNU Lesser General Public
13     License along with this library; if not, write to the 
14     Free Software Foundation, Inc., 59 Temple Place, Suite 330, 
15     Boston, MA 02111-1307  USA
16     
17     You can contact Elliotte Rusty Harold by sending e-mail to
18     elharo@metalab.unc.edu. Please include the word "XOM" in the
19     subject line. The XOM home page is located at http://www.xom.nu/
20  */
21  
22  package nu.xom.xinclude;
23  
24  /**
25   * <p>
26   * Indicates an error as defined by the XPoiner specification.
27   * </p>
28   *
29   * @author Elliotte Rusty Harold
30   * @version 1.0
31   */
32  class XPointerException extends Exception   {
33  
34      private Throwable   cause = null;
35  
36      /**
37       * <p>
38       * Constructs an <code>XPointerException</code> with the 
39       * specified detail message.
40       * </p>
41       *
42       * @param message a string indicating the specific problem
43       */
44      XPointerException(String   message) {
45          super(message);
46      }
47  
48      
49      /**
50       * <p>
51       * Constructs an <code>XPointerException</code> with the 
52       * specified detail message and root cause.
53       * </p>
54       * 
55       * @param message a string indicating the specific problem
56       * @param cause the initial exception which caused this 
57       *     <code>XPointerException</code>
58       */
59      XPointerException(String   message, Throwable   cause) {
60          super(message);
61          initCause(cause);
62      }
63  
64      
65      /**
66       * <p>
67       * When an <code>IOException</code>,  
68       * <code>MalformedURLException</code>, or other generic  
69       * exception is thrown while processing an XML document
70       * for XPointer, it is customarily replaced
71       * by some form of <code>XPointerSyntaxException</code>.  
72       * This method allows you to retrieve the original exception.
73       * It returns null if no such exception caused this 
74       * <code>XPointerSyntaxException</code>.
75       *</p>
76       * 
77       * @return the underlying exception which 
78       *     caused this XPointerSyntaxException to be thrown
79       */
80      public Throwable   getCause() {
81          return this.cause;  
82      }
83  
84      
85      // null is insufficient for detecting an uninitialized cause.
86      // The cause may be set to null which may not then be reset.
87      private boolean causeSet = false;
88  
89      
90      /**
91       * <p>
92       * When an <code>IOException</code>,  
93       * <code>MalformedURLException</code>, or other generic exception 
94       * is thrown while processing an XML document
95       * for XPointers, it is customarily replaced
96       * by some form of <code>XPointerException</code>.  
97       * This method allows you to store the original exception.
98       * </p>
99       *
100      * @param cause the root cause of this exception
101      * 
102      * @return this <code>XPointerException</code>
103      * 
104      * @throws IllegalArgumentException if the cause is this exception
105      *   (An exception cannot be its own cause.)
106      * @throws IllegalStateException if this method is called twice
107      */
108     public Throwable   initCause(Throwable   cause) {
109         if (causeSet) {
110             throw new IllegalStateException  ("Can't overwrite cause");
111         } 
112         else if (cause == this) {
113             throw new IllegalArgumentException  ("Self-causation not permitted"); 
114         }
115         else this.cause = cause;
116         causeSet = true;
117         return this;
118     }
119 
120     
121 }
122
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