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: 1.4 $ $Date: 2003/08/09 15:49:50 $
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
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