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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/SimpleFunctionContext.java,v 1.12 2005/09/25 11:39:21 elharo Exp $
3    * $Revision: 1.12 $
4    * $Date: 2005/09/25 11:39:21 $
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 1.12 2005/09/25 11:39:21 elharo Exp $
60   */
61  
62  
63  package org.jaxen;
64  
65  import java.util.HashMap;
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 functions;
83  
84      /*** 
85       *  <p>
86       *  Construct an empty function context.
87       *  </p>
88       */
89      public SimpleFunctionContext()
90      {
91          this.functions = new HashMap();
92      }
93  
94      /*** Register a new function.
95       *
96       *  <p>
97       *  By registering a new function, any XPath expression
98       *  that utilizes this <code>FunctionContext</code> may
99       *  refer to and use the new function.
100      *  </p>
101      *
102      *  <p>
103      *  Functions may exist either in a namespace or not.
104      *  Namespace prefix-to-URI resolution is the responsibility
105      *  of a {@link NamespaceContext}.  Within this <code>FunctionContext</code>
106      *  functions are only referenced using the URI, <strong>not</strong>
107      *  the prefix.
108      *  </p>
109      *
110      *  <p>
111      *  The namespace URI of a function may be <code>null</code>
112      *  to indicate that it exists without a namespace.
113      *  </p>
114      *
115      *  @param namespaceURI the namespace URI of the function to
116      *         be registered with this context
117      *  @param localName the non-prefixed local portion of the
118      *         function to be registered with this context
119      *  @param function a {@link Function} implementation object
120      *         to be used when evaluating the function
121      */
122     public void registerFunction(String namespaceURI,
123                                  String localName,
124                                  Function function )
125     {
126         this.functions.put( new QualifiedName(namespaceURI, null, localName),
127                             function );
128     }
129 
130     public Function getFunction(String namespaceURI,
131                                 String prefix,
132                                 String localName )
133         throws UnresolvableException
134     {
135         QualifiedName key = new QualifiedName( namespaceURI, prefix, localName );
136 
137         if ( this.functions.containsKey(key) ) {
138             return (Function) this.functions.get( key );
139         }
140         else {
141             throw new UnresolvableException( "No Such Function " + key.getClarkForm() );
142         }
143     }
144 }