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 } 52