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1   /***
2    * Redistribution and use of this software and associated documentation
3    * ("Software"), with or without modification, are permitted provided
4    * that the following conditions are met:
5    *
6    * 1. Redistributions of source code must retain copyright
7    *    statements and notices.  Redistributions must also contain a
8    *    copy of this document.
9    *
10   * 2. Redistributions in binary form must reproduce the
11   *    above copyright notice, this list of conditions and the
12   *    following disclaimer in the documentation and/or other
13   *    materials provided with the distribution.
14   *
15   * 3. The name "Exolab" must not be used to endorse or promote
16   *    products derived from this Software without prior written
17   *    permission of Exoffice Technologies.  For written permission,
18   *    please contact info@exolab.org.
19   *
20   * 4. Products derived from this Software may not be called "Exolab"
21   *    nor may "Exolab" appear in their names without prior written
22   *    permission of Exoffice Technologies. Exolab is a registered
23   *    trademark of Exoffice Technologies.
24   *
25   * 5. Due credit should be given to the Exolab Project
26   *    (http://www.exolab.org/).
27   *
28   * THIS SOFTWARE IS PROVIDED BY EXOFFICE TECHNOLOGIES AND CONTRIBUTORS
29   * ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT
30   * NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
31   * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL
32   * EXOFFICE TECHNOLOGIES OR ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
33   * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
34   * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
35   * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
36   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
37   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
38   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
39   * OF THE POSSIBILITY OF SUCH DAMAGE.
40   *
41   * Copyright 2000-2001,2003 (C) Exoffice Technologies Inc. All Rights Reserved.
42   */
43  
44  package org.exolab.jms.selector;
45  
46  
47  /***
48   * Utility class for casting from an SObject to a derived class,
49   * raising a TypeMismatchException if the operation is invalid.
50   *
51   * @version     $Revision: 1.1 $ $Date: 2004/11/26 01:50:45 $
52   * @author      <a href="mailto:tma@netspace.net.au">Tim Anderson</a>
53   * @see         Expression
54   * @see         SBool
55   * @see         SNumber
56   * @see         SString
57   * @see         TypeMismatchException
58   */
59  final class TypeCaster {
60  
61      /***
62       * Private constructor
63       */
64      private TypeCaster() {
65      }
66  
67      /***
68       * Cast an object to boolean
69       *
70       * @param obj the object to cast
71       * @param context the context where the object was created
72       * @return the cast object
73       * @throws TypeMismatchException if <code>obj</code> can't be cast
74       */
75      public static SBool castToBool(final SObject obj, final String context)
76          throws TypeMismatchException {
77  
78          SBool result = null;
79          if (obj instanceof SBool) {
80              result = (SBool) obj;
81          } else if (obj != null) {
82              typeMismatch(Type.BOOLEAN, obj, context);
83          }
84          return result;
85      }
86  
87      /***
88       * Cast an object to numeric
89       *
90       * @param obj the object to cast
91       * @param context the context where the object was created
92       * @return the cast object
93       * @throws TypeMismatchException if <code>obj</code> can't be cast
94       */
95      public static SNumber castToNumber(final SObject obj, final String context)
96          throws TypeMismatchException {
97  
98          SNumber result = null;
99          if (obj instanceof SNumber) {
100             result = (SNumber) obj;
101         } else if (obj != null) {
102             typeMismatch(Type.NUMERIC, obj, context);
103         }
104         return result;
105     }
106 
107     /***
108      * Cast an object to string
109      *
110      * @param obj the object to cast
111      * @param context the context where the object was created
112      * @return the cast object
113      * @throws TypeMismatchException if <code>obj</code> can't be cast
114      */
115     public static SString castToString(final SObject obj, final String context)
116         throws TypeMismatchException {
117 
118         SString result = null;
119         if (obj instanceof SString) {
120             result = (SString) obj;
121         } else if (obj != null) {
122             typeMismatch(Type.STRING, obj, context);
123         }
124         return result;
125     }
126 
127     /***
128      * Raises a type mismatch exception
129      *
130      * @param expected the expected type
131      * @param value the actual value
132      * @param context the context where <code>value</code> was created
133      * @throws TypeMismatchException corresponding to the expected and actual
134      * values
135      */
136     private static void typeMismatch(final Type expected, final SObject value,
137                                      final String context)
138         throws TypeMismatchException {
139 
140         StringBuffer msg = new StringBuffer();
141         msg.append("expecting a ");
142         msg.append(expected);
143         msg.append(" expression");
144         if (context != null) {
145             msg.append(" for ");
146             msg.append(context);
147         }
148         msg.append(", found a ");
149         msg.append(value.type());
150         throw new TypeMismatchException(msg.toString());
151     }
152 
153 } //-- TypeCaster