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Java > Open Source Codes > org > exolab > jms > selector > Or


1 /**
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42  */
43
44 package org.exolab.jms.selector;
45
46 import javax.jms.Message JavaDoc;
47
48
49 /**
50  * This class implements an 'and' expression.
51  *
52  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
53  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
54  * @see Expression
55  * @see LogicalOperator
56  * @see SBool
57  */
58 class Or extends LogicalOperator {
59
60     /**
61      * The expression context, for error reporting purposes
62      */
63     private static final String JavaDoc CONTEXT = "or operator";
64
65     /**
66      * Construct a new <code>And</code> operator
67      *
68      * @param lhs the left hand side of the expression
69      * @param rhs the right hand side of the expression
70      */
71     public Or(final Expression lhs, final Expression rhs) {
72         super("or", lhs, rhs);
73     }
74
75     /**
76      * Evaluate the expression
77      *
78      * @param msg the message to use to obtain any header identifier and
79      * property values
80      * @return the evaluated result, or <code>null</code> if the value of the
81      * expression is unknown
82      * @throws TypeMismatchException if the expression tries to evaluate
83      * mismatched types.
84      */
85     public SObject evaluate(final Message JavaDoc msg) throws TypeMismatchException {
86         SBool result = null;
87         SBool lhs = TypeCaster.castToBool(left().evaluate(msg), CONTEXT);
88         if (lhs != null) {
89             if (lhs.value()) {
90                 result = SBool.TRUE;
91             } else {
92                 SBool rhs = TypeCaster.castToBool(right().evaluate(msg),
93                     CONTEXT);
94                 result = lhs.or(rhs);
95             }
96         } else {
97             SBool rhs = TypeCaster.castToBool(right().evaluate(msg), CONTEXT);
98             if (rhs != null) {
99                 result = rhs.or(lhs);
100             }
101         }
102         return result;
103     }
104
105 } //-- Or
106
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