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


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.
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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
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38  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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40  *
41  * Copyright 2000-2001,2003 (C) Exoffice Technologies Inc. All Rights Reserved.
42  */
43
44 package org.exolab.jms.selector;
45
46 import org.apache.oro.text.regex.MalformedPatternException;
47 import org.apache.oro.text.regex.Pattern;
48 import org.apache.oro.text.regex.Perl5Compiler;
49
50
51 /**
52  * Regular expression factory. This creates a regular expression for a given
53  * SQL92 pattern and escape character.
54  *
55  * @version $Revision: 1.1 $ $Date: 2004/11/26 01:50:44 $
56  * @author <a HREF="mailto:tma@netspace.net.au">Tim Anderson</a>
57  */
58 final class RegexpFactory {
59
60     /**
61      * Private constructor
62      */
63     private RegexpFactory() {
64     }
65
66     /**
67      * Converts the pattern and escape to an ORO <code>Pattern</code>
68      *
69      * @param pattern the pattern
70      * @param escape the escape character. May be null
71      * @return an ORO <code>Pattern</code> corresponding to
72      * <code>pattern</code> and <code>escape</code>
73      * @throws InvalidRegexpException if <code>pattern</code> or
74      * <code>escape</code> are invalid
75      */
76     public static Pattern create(final String JavaDoc pattern, final Character JavaDoc escape)
77         throws InvalidRegexpException {
78         StringBuffer JavaDoc buff = new StringBuffer JavaDoc();
79         buff.append('^');
80
81         for (int i = 0; i < pattern.length(); ++i) {
82             boolean escaped = false;
83             char ch = pattern.charAt(i);
84             if (escape != null && ch == escape.charValue()) {
85                 if (++i < pattern.length()) {
86                     ch = pattern.charAt(i);
87                     escaped = true;
88                 } else {
89                     throw new InvalidRegexpException(pattern);
90                 }
91             }
92
93             switch (ch) {
94                 case '_':
95                     if (escaped) {
96                         buff.append(ch);
97                     } else {
98                         buff.append('.');
99                     }
100                     break;
101                 case '%':
102                     if (escaped) {
103                         buff.append(ch);
104                     } else {
105                         buff.append(".*");
106                     }
107                     break;
108                 case '.':
109                 case '[':
110                 case ']':
111                 case '\\':
112                 case '+':
113                 case '?':
114                 case '{':
115                 case '}':
116                 case '$':
117                 case '^':
118                 case '|':
119                 case '(':
120                 case ')':
121                     // the above are all special characters that need to be
122 // escaped.
123 buff.append('\\');
124                     buff.append(ch);
125                     break;
126                 default:
127                     buff.append(ch);
128             }
129         }
130         buff.append('$');
131
132         Pattern result = null;
133         try {
134             Perl5Compiler compiler = new Perl5Compiler();
135             result = compiler.compile(buff.toString());
136         } catch (MalformedPatternException exception) {
137             // coding error if this gets thrown here...
138 throw new InvalidRegexpException(pattern);
139         }
140         return result;
141     }
142
143 } //-- RegexpFactory
144
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