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 (C) Exoffice Technologies Inc. All Rights Reserved.
42 */
43
44 package org.exolab.jms.selector;
45
46 import javax.jms.Message;
47
48
49 /***
50 * This class is the base class for all expressions that are boolean binary
51 * operators. These return a boolean result when evaluated, or null
52 * if the result is undefined.
53 *
54 * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
55 * @author <a href="mailto:tima@intalio.com">Tim Anderson</a>
56 * @see Expression
57 * @see SBool
58 */
59 abstract class LogicalOperator extends BinaryOperator {
60
61 /***
62 * Construct a new <code>LogicalOperator</code>
63 *
64 * @param operator the operator
65 * @param lhs the left hand side of the expression
66 * @param rhs the right hand side of the expression
67 */
68 protected LogicalOperator(final String operator, final Expression lhs,
69 final Expression rhs) {
70 super(operator, lhs, rhs);
71 }
72
73 /***
74 * Evaluate the expression
75 *
76 * @param msg the message to use to obtain any header identifier and
77 * property values
78 * @return the evaluated result, or <code>null</code> if the value of the
79 * expression is unknown
80 * @throws TypeMismatchException if the expression tries to evaluate
81 * mismatched types.
82 */
83 public SObject evaluate(final Message msg) throws TypeMismatchException {
84 SBool result = null;
85
86 SObject lhs = left().evaluate(msg);
87 if (lhs != null) {
88 SObject rhs = right().evaluate(msg);
89 if (rhs != null) {
90 checkTypes(lhs.type(), rhs.type());
91 result = evaluate(lhs, rhs);
92 }
93 }
94 return result;
95 }
96
97 /***
98 * Perform a logical comparison
99 *
100 * @param lhs the left hand side of the expression
101 * @param rhs the right hand side of the expression
102 * @return the evaluated result
103 */
104 protected SBool evaluate(final SObject lhs, final SObject rhs) {
105 return null;
106 }
107
108 /***
109 * Verifies that the types of expression can be verified.
110 *
111 * @param lhs the left hand side of the expression
112 * @param rhs the right hand side of the expression
113 * @throws TypeMismatchException if the types cannot be compared
114 */
115 protected void checkTypes(final Type lhs, final Type rhs)
116 throws TypeMismatchException {
117 if (lhs != rhs) {
118 StringBuffer msg = new StringBuffer();
119 msg.append("expecting a ");
120 msg.append(lhs);
121 msg.append(" expression for operator ");
122 msg.append(operator());
123 msg.append(", found a ");
124 msg.append(rhs);
125 throw new TypeMismatchException(msg.toString());
126 }
127 }
128
129 }
130