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1 /**
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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 And extends LogicalOperator {
59
60     /**
61      * The expression context, for error reporting purposes
62      */
63     private static final String JavaDoc CONTEXT = "and operator";
64
65
66     /**
67      * Construct a new <code>And</code> operator
68      *
69      * @param lhs the left hand side of the expression
70      * @param rhs the right hand side of the expression
71      */
72     public And(final Expression lhs, final Expression rhs) {
73         super("and", lhs, rhs);
74     }
75
76     /**
77      * Evaluate the expression
78      *
79      * @param msg the message to use to obtain any header identifier and
80      * property values
81      * @return the evaluated result, or <code>null</code> if the value of the
82      * expression is unknown
83      * @throws TypeMismatchException if the expression tries to evaluate
84      * mismatched types.
85      */
86     public final SObject evaluate(final Message JavaDoc msg)
87         throws TypeMismatchException {
88         SBool result = null;
89         SBool lhs = TypeCaster.castToBool(left().evaluate(msg), CONTEXT);
90         if (lhs != null) {
91             if (!lhs.value()) {
92                 result = SBool.FALSE;
93             } else {
94                 SBool rhs = TypeCaster.castToBool(right().evaluate(msg),
95                     CONTEXT);
96                 result = lhs.and(rhs);
97             }
98         } else {
99             SBool rhs = TypeCaster.castToBool(right().evaluate(msg), CONTEXT);
100             if (rhs != null) {
101                 result = rhs.and(lhs);
102             }
103         }
104         return result;
105     }
106
107 } //-- And
108
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