1. // $Id: XPathFunctionResolver.java,v 1.7 2004/04/01 16:07:17 ndw Exp $

  2. 

  3. /*

  4.  * @(#)XPathFunctionResolver.java	1.6 04/07/26

  5.  * 

  6.  * Copyright 2004 Sun Microsystems, Inc. All rights reserved.

  7.  * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.

  8.  */

  9. 

  10. package javax.xml.xpath;

  11. 

  12. import javax.xml.namespace.QName;

  13. 

  14. /**

  15.  * <p><code>XPathFunctionResolver</code> provides access to the set of user defined <code>XPathFunction</code>s.</p>

  16.  *

  17.  * <p>XPath functions are resolved by name and arity.

  18.  * The resolver is not needed for XPath built-in functions and the resolver

  19.  * <strong><em>cannot</em></strong> be used to override those functions.</p>

  20.  *

  21.  * <p>In particular, the resolver is only called for functions in an another

  22.  * namespace (functions with an explicit prefix). This means that you cannot

  23.  * use the <code>XPathFunctionResolver</code> to implement specifications

  24.  * like <a href="http://www.w3.org/TR/xmldsig-core/">XML-Signature Syntax

  25.  * and Processing</a> which extend the function library of XPath 1.0 in the

  26.  * same namespace. This is a consequence of the design of the resolver.</p>

  27.  *

  28.  * <p>If you wish to implement additional built-in functions, you will have to

  29.  * extend the underlying implementation directly.</p>

  30.  *

  31.  * @author  <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>

  32.  * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>

  33.  * @version $Revision: 1.7 $, $Date: 2004/04/01 16:07:17 $

  34.  * @see <a href="http://www.w3.org/TR/xpath#corelib">XML Path Language (XPath) Version 1.0, Core Function Library</a>

  35.  * @since 1.5

  36.  */

  37. public interface XPathFunctionResolver {

  38.   /** 

  39.    * <p>Find a function in the set of available functions.</p>

  40.    * 

  41.    * <p>If <code>functionName</code> or <code>arity</code> is <code>null</code>, then a <code>NullPointerException</code> is thrown.</p>

  42.    *

  43.    * @param functionName The function name.

  44.    * @param arity The number of arguments that the returned function must accept.

  45.    * 

  46.    * @return The function or <code>null</code> if no function named <code>functionName</code> with <code>arity</code> arguments exists.

  47.    * 

  48.    * @throws NullPointerException If <code>functionName</code> or <code>arity</code> is <code>null</code>.

  49.    */

  50.   public XPathFunction resolveFunction(QName functionName, int arity);

  51. }