View Javadoc

1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/SimpleFunctionContext.java,v 1.14 2006/02/05 21:47:41 elharo Exp $
3    * $Revision: 1.14 $
4    * $Date: 2006/02/05 21:47:41 $
5    *
6    * ====================================================================
7    *
8    * Copyright 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 are
13   * met:
14   * 
15   *   * Redistributions of source code must retain the above copyright
16   *     notice, this list of conditions and the following disclaimer.
17   * 
18   *   * Redistributions in binary form must reproduce the above copyright
19   *     notice, this list of conditions and the following disclaimer in the
20   *     documentation and/or other materials provided with the distribution.
21   * 
22   *   * Neither the name of the Jaxen Project nor the names of its
23   *     contributors may be used to endorse or promote products derived 
24   *     from this software without specific prior written permission.
25   * 
26   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37   *
38   * ====================================================================
39   * This software consists of voluntary contributions made by many 
40   * individuals on behalf of the Jaxen Project and was originally 
41   * created by bob mcwhirter <bob@werken.com> and 
42   * James Strachan <jstrachan@apache.org>.  For more information on the 
43   * Jaxen Project, please see <http://www.jaxen.org/>.
44   * 
45   * $Id: SimpleFunctionContext.java,v 1.14 2006/02/05 21:47:41 elharo Exp $
46   */
47  
48  
49  package org.jaxen;
50  
51  import java.util.HashMap;
52  
53  /*** Simple default implementation of <code>FunctionContext</code>.
54   *
55   *  <p>
56   *  This is a simple table-based key-lookup implementation
57   *  for <code>FunctionContext</code> which can be programmatically
58   *  extended by registering additional functions.
59   *  </p>
60   *
61   *  @see XPathFunctionContext
62   *
63   *  @author <a href="mailto:bob@werken.com">bob mcwhirter</a>
64   */
65  public class SimpleFunctionContext implements FunctionContext
66  {
67      /*** Table of functions. */
68      private HashMap functions;
69  
70      /*** 
71       *  <p>
72       *  Construct an empty function context.
73       *  </p>
74       */
75      public SimpleFunctionContext()
76      {
77          this.functions = new HashMap();
78      }
79  
80      /*** Register a new function.
81       *
82       *  <p>
83       *  By registering a new function, any XPath expression
84       *  that utilizes this <code>FunctionContext</code> may
85       *  refer to and use the new function.
86       *  </p>
87       *
88       *  <p>
89       *  Functions may exist either in a namespace or not.
90       *  Namespace prefix-to-URI resolution is the responsibility
91       *  of a {@link NamespaceContext}.  Within this <code>FunctionContext</code>
92       *  functions are only referenced using the URI, <strong>not</strong>
93       *  the prefix.
94       *  </p>
95       *
96       *  <p>
97       *  The namespace URI of a function may be <code>null</code>
98       *  to indicate that it exists without a namespace.
99       *  </p>
100      *
101      *  @param namespaceURI the namespace URI of the function to
102      *         be registered with this context
103      *  @param localName the non-prefixed local portion of the
104      *         function to be registered with this context
105      *  @param function a {@link Function} implementation object
106      *         to be used when evaluating the function
107      */
108     public void registerFunction(String namespaceURI,
109                                  String localName,
110                                  Function function )
111     {
112         this.functions.put( new QualifiedName(namespaceURI, localName),
113                             function );
114     }
115 
116     public Function getFunction(String namespaceURI,
117                                 String prefix,
118                                 String localName )
119         throws UnresolvableException
120     {
121         QualifiedName key = new QualifiedName( namespaceURI, localName );
122 
123         if ( this.functions.containsKey(key) ) {
124             return (Function) this.functions.get( key );
125         }
126         else {
127             throw new UnresolvableException( "No Such Function " + key.getClarkForm() );
128         }
129     }
130 }