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Java > Open Source Codes > org > exolab > jms > selector > parser > TypeChecker


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43
44 package org.exolab.jms.selector.parser;
45
46 import org.exolab.jms.selector.Identifiers;
47 import org.exolab.jms.selector.Type;
48 import org.exolab.jms.selector.TypeMismatchException;
49
50
51 /**
52  * Utility class for performing type checking
53  *
54  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:45 $
55  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
56  * @see SelectorAST
57  * @see SelectorTreeParser
58  * @see Type
59  * @see TypeMismatchException
60  */

61 final class TypeChecker {
62
63     /**
64      * Private constructor
65      */

66     private TypeChecker() {
67     }
68
69     /**
70      * Checks the return type of an expression against the expected type
71      *
72      * @param node the expression node
73      * @param expected the expected type of the expression
74      * @throws TypeMismatchException if the return type doesn't match that
75      * expected
76      */

77     public static void check(final SelectorAST node, final Type expected)
78         throws TypeMismatchException {
79
80         Type type = node.getReturnType();
81         if (type != expected && type != Type.UNDEFINED) {
82             String JavaDoc msg = "expecting a " + expected + " expression, found a "
83                 + type;
84             throw new TypeMismatchException(node.getContext(), msg);
85         }
86     }
87
88     /**
89      * Checks the return type of an expression against the expected type
90      *
91      * @param operator the expression operator
92      * @param node the expression node
93      * @param expected the expected type of the expression
94      * @throws TypeMismatchException if the return type doesn't match that
95      * expected
96      */

97     public static void check(final String JavaDoc operator, final SelectorAST node,
98                              final Type expected)
99         throws TypeMismatchException {
100
101         Type type = node.getReturnType();
102         if (type != expected && type != Type.UNDEFINED) {
103             String JavaDoc msg = "expecting a " + expected
104                 + " expression for operator " + operator + ", found a " + type;
105             throw new TypeMismatchException(node.getContext(), msg);
106         }
107     }
108
109     /**
110      * Checks the types of left and right hand sides of an expression against
111      * the expected type
112      *
113      * @param operator the expression operator
114      * @param left the left hand side of the expression
115      * @param right the right hand side of the expression
116      * @param expected the expected type of the expression
117      * @throws TypeMismatchException if a type doesn't match that expected
118      */

119     public static void check(final String JavaDoc operator, final SelectorAST left,
120                              final SelectorAST right, final Type expected)
121         throws TypeMismatchException {
122
123         check(operator, left, expected);
124         check(operator, right, expected);
125     }
126
127     /**
128      * Verifies if two expressions can be compared
129      *
130      * @param operator the comparison operator
131      * @param left the left hand side of the expression
132      * @param right the right hand side of the expression
133      * @throws TypeMismatchException if the expressions can't be compared
134      */

135     public static void checkComparison(final String JavaDoc operator,
136                                        final SelectorAST left,
137                                        final SelectorAST right)
138         throws TypeMismatchException {
139
140         Type lhs = left.getReturnType();
141         Type rhs = right.getReturnType();
142
143         if (lhs == Type.UNDEFINED || rhs == Type.UNDEFINED) {
144             // can't evaluate this at parse time.
145
} else if (lhs == Type.STRING && rhs == Type.STRING) {
146             checkStringComparison(operator, left, right);
147         } else if ((lhs == Type.STRING && rhs != Type.STRING)
148                    || (lhs == Type.BOOLEAN && rhs != Type.BOOLEAN)
149                    || (lhs == Type.NUMERIC && rhs != Type.NUMERIC)) {
150             String JavaDoc msg = "expecting a " + lhs + " expression for operator "
151                 + operator + ", found a " + rhs;
152             throw new TypeMismatchException(right.getContext(), msg);
153         }
154     }
155
156     /**
157      * Verifies if two string expressions can be compared
158      *
159      * @param operator the comparison operator
160      * @param left the left hand side of the expression
161      * @param right the right hand side of the expression
162      * @throws TypeMismatchException if the expressions can't be compared
163      */

164     public static void checkStringComparison(final String JavaDoc operator,
165                                              final SelectorAST left,
166                                              final SelectorAST right)
167         throws TypeMismatchException {
168         if (left.getType() == SelectorTokenTypes.IDENT
169             && right.getType() == SelectorTokenTypes.STRING_LITERAL) {
170             checkIdentifierComparison(left, right);
171         } else if (left.getType() == SelectorTokenTypes.STRING_LITERAL
172                    && right.getType() == SelectorTokenTypes.IDENT) {
173             checkIdentifierComparison(right, left);
174         }
175     }
176
177     /**
178      * Verifies that an identifier may be compared to a string literal
179      *
180      * @param identifier the identifier
181      * @param literal the string literal
182      * @throws TypeMismatchException if the expressions can't be compared
183      */

184     public static void checkIdentifierComparison(final SelectorAST identifier,
185                                                  final SelectorAST literal)
186         throws TypeMismatchException {
187         if (identifier.getText().equals(Identifiers.JMS_DELIVERY_MODE)) {
188             String JavaDoc value = literal.getText();
189             if (!value.equals(Identifiers.PERSISTENT)
190                 && !value.equals(Identifiers.NON_PERSISTENT)) {
191                 String JavaDoc msg = "Cannot compare JMSDeliveryMode with '"
192                     + value + "'";
193                 throw new TypeMismatchException(identifier.getContext(), msg);
194             }
195         }
196     }
197
198 } //-- TypeChecker
199
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