http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// $Id: XPathFunction.java 446598 2006-09-15 12:55:40Z jeremias $

package javax.xml.xpath;

import java.util.List;


XPathFunction provides access to XPath functions.


Functions are identified by QName and arity in XPath.


Author: Norman Walsh,  Jeff Suttor
Version:$Revision: 446598 $, $Date: 2006-09-15 08:55:40 -0400 (Fri, 15 Sep 2006) $
Since:1.5
/**
 * <p><code>XPathFunction</code> provides access to XPath functions.</p>
 *
 * <p>Functions are identified by QName and arity in XPath.</p>
 *
 * @author  <a href="mailto:Norman.Walsh@Sun.com">Norman Walsh</a>
 * @author  <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @version $Revision: 446598 $, $Date: 2006-09-15 08:55:40 -0400 (Fri, 15 Sep 2006) $
 * @since 1.5
 */
public interface XPathFunction {
  
Evaluate the function with the specified arguments.


To the greatest extent possible, side-effects should be avoided in the
definition of extension functions. The implementation evaluating an
XPath expression is under no obligation to call extension functions in
any particular order or any particular number of times.


Params:
  • args – The arguments, null is a valid value.
Throws:
Returns:The result of evaluating the XPath function as an Object.
/**
   * <p>Evaluate the function with the specified arguments.</p>
   *
   * <p>To the greatest extent possible, side-effects should be avoided in the
   * definition of extension functions. The implementation evaluating an
   * XPath expression is under no obligation to call extension functions in
   * any particular order or any particular number of times.</p>
   * 
   * @param args The arguments, <code>null</code> is a valid value.
   * 
   * @return The result of evaluating the <code>XPath</code> function as an <code>Object</code>.
   * 
   * @throws XPathFunctionException If <code>args</code> cannot be evaluated with this <code>XPath</code> function.
   */
  public Object evaluate(List args)
    throws XPathFunctionException;
}