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1 /*
2  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/SimpleFunctionContext.java,v 1.9 2005/03/23 13:12:54 elharo Exp $
3  * $Revision: 1.9 $
4  * $Date: 2005/03/23 13:12:54 $
5  *
6  * ====================================================================
7  *
8  * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  *
15  * 1. Redistributions of source code must retain the above copyright
16  * notice, this list of conditions, and the following disclaimer.
17  *
18  * 2. Redistributions in binary form must reproduce the above copyright
19  * notice, this list of conditions, and the disclaimer that follows
20  * these conditions in the documentation and/or other materials
21  * provided with the distribution.
22  *
23  * 3. The name "Jaxen" must not be used to endorse or promote products
24  * derived from this software without prior written permission. For
25  * written permission, please contact license@jaxen.org.
26  *
27  * 4. Products derived from this software may not be called "Jaxen", nor
28  * may "Jaxen" appear in their name, without prior written permission
29  * from the Jaxen Project Management (pm@jaxen.org).
30  *
31  * In addition, we request (but do not require) that you include in the
32  * end-user documentation provided with the redistribution and/or in the
33  * software itself an acknowledgement equivalent to the following:
34  * "This product includes software developed by the
35  * Jaxen Project (http://www.jaxen.org/)."
36  * Alternatively, the acknowledgment may be graphical using the logos
37  * available at http://www.jaxen.org/
38  *
39  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42  * DISCLAIMED. IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50  * SUCH DAMAGE.
51  *
52  * ====================================================================
53  * This software consists of voluntary contributions made by many
54  * individuals on behalf of the Jaxen Project and was originally
55  * created by bob mcwhirter <bob@werken.com> and
56  * James Strachan <jstrachan@apache.org>. For more information on the
57  * Jaxen Project, please see <http://www.jaxen.org/>.
58  *
59  * $Id: SimpleFunctionContext.java,v 1.9 2005/03/23 13:12:54 elharo Exp $
60  */
61
62
63 package org.jaxen;
64
65 import java.util.HashMap JavaDoc;
66
67 /** Simple default implementation of <code>FunctionContext</code>.
68  *
69  * <p>
70  * This is a simple table-based key-lookup implementation
71  * for <code>FunctionContext</code> which can be programmatically
72  * extended by registering additional functions.
73  * </p>
74  *
75  * @see XPathFunctionContext
76  *
77  * @author <a HREF="mailto:bob@werken.com">bob mcwhirter</a>
78  */
79 public class SimpleFunctionContext implements FunctionContext
80 {
81     /** Table of functions. */
82     private HashMap JavaDoc functions;
83
84     /** Construct.
85      *
86      * <p>
87      * Construct with an empty function lookup table.
88      * </p>
89      */
90     public SimpleFunctionContext()
91     {
92         this.functions = new HashMap JavaDoc();
93     }
94
95     /** Register a new function.
96      *
97      * <p>
98      * By registering a new function, any XPath expression
99      * that utilizes this <code>FunctionContext</code> may
100      * refer to and use the new function.
101      * </p>
102      *
103      * <p>
104      * Functions may exist either in an namespace or not.
105      * Namespace prefix-to-URI resolution is the responsibility
106      * of a {@link NamespaceContext}. Within this <code>FunctionContext</code>
107      * functions are only referenced using the URI, <b>not</b>
108      * the prefix.
109      * </p>
110      *
111      * <p>
112      * The namespace URI of a function may be <code>null</code>
113      * to indicate that it exists without a namespace.
114      * </p>
115      *
116      * @param namespaceURI the namespace URI of the function to
117      * be registered with this context
118      * @param localName the non-prefixed local portion of the
119      * function to be registered with this context
120      * @param function a {@link Function} implementation object
121      * to be used when evaluating the function
122      */
123     public void registerFunction(String JavaDoc namespaceURI,
124                                  String JavaDoc localName,
125                                  Function function )
126     {
127         this.functions.put( new QualifiedName(namespaceURI, localName),
128                             function );
129     }
130
131     public Function getFunction(String JavaDoc namespaceURI,
132                                 String JavaDoc prefix,
133                                 String JavaDoc localName )
134         throws UnresolvableException
135     {
136         Object JavaDoc key = new QualifiedName( namespaceURI, localName );
137
138         if ( this.functions.containsKey(key) ) {
139             return (Function) this.functions.get( key );
140         }
141         else {
142             throw new UnresolvableException( "Function " +
143                                              prefix + ":" + localName );
144         }
145     }
146 }
147
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