code: /*
   * 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.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package org.apache.xalan.extensions;
  
  import java.util.List;
  import java.util.Vector;
  
  import javax.xml.transform.TransformerException;
  import javax.xml.xpath.XPathFunction;
  import javax.xml.xpath.XPathFunctionException;
  
  /**
   * A sample implementation of XPathFunction, with support for
   * EXSLT extension functions and Java extension functions.
   */
  public class XPathFunctionImpl implements XPathFunction
  {
      private ExtensionHandler m_handler;
      private String m_funcName;
      
      /**
       * Construct an instance of XPathFunctionImpl from the
       * ExtensionHandler and function name.
       */
      public XPathFunctionImpl(ExtensionHandler handler, String funcName)
      {
          m_handler = handler;
          m_funcName = funcName;
      }
          
      /**
       * @see javax.xml.xpath.XPathFunction#evaluate(java.util.List)
       */
      public Object evaluate(List args)
          throws XPathFunctionException
      {
          Vector  argsVec = listToVector(args);
          
          try {
              // The method key and ExpressionContext are set to null.
              return m_handler.callFunction(m_funcName, argsVec, null, null);
          }
          catch (TransformerException e)
          {
              throw new XPathFunctionException(e);
          }
      }
      
      /**
       * Convert a java.util.List to a java.util.Vector. 
       * No conversion is done if the List is already a Vector.
       */
      private static Vector listToVector(List args)
      {
          if (args == null)
              return null;
          else if (args instanceof Vector)
              return (Vector)args;
          else
          {
              Vector result = new Vector();
              result.addAll(args);
              return result;
          }        
      }
  }
  