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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;
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      /*** Construct.
85       *
86       *  <p>
87       *  Construct with an empty function lookup table.
88       *  </p>
89       */
90      public SimpleFunctionContext()
91      {
92          this.functions = new HashMap();
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 namespaceURI,
124                                  String localName,
125                                  Function function )
126     {
127         this.functions.put( new QualifiedName(namespaceURI, localName),
128                             function );
129     }
130 
131     public Function getFunction(String namespaceURI,
132                                 String prefix,
133                                 String localName )
134         throws UnresolvableException
135     {
136         Object 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 }