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 javax.xml.namespace.QName;
  import javax.xml.xpath.XPathFunction;
  import javax.xml.xpath.XPathFunctionResolver;
  import org.apache.xalan.res.XSLMessages;
  import org.apache.xalan.res.XSLTErrorResources;
  
  /**
   * A sample implementation of XPathFunctionResolver, with support for
   * EXSLT extension functions and Java extension functions.
   */
  public class XPathFunctionResolverImpl implements XPathFunctionResolver
  {
      /**
       * Resolve an extension function from the qualified name and arity.
       */
      public XPathFunction resolveFunction(QName qname, int arity)
      {
          if (qname == null)
              throw new NullPointerException(
                  XSLMessages.createMessage(
                      XSLTErrorResources.ER_XPATH_RESOLVER_NULL_QNAME, null));
          
          if (arity < 0)
              throw new IllegalArgumentException(
                  XSLMessages.createMessage(
                      XSLTErrorResources.ER_XPATH_RESOLVER_NEGATIVE_ARITY, null));
          
          String uri = qname.getNamespaceURI();
          if (uri == null || uri.length() == 0)
              return null;
          
          String className = null;
          String methodName = null;
          if (uri.startsWith("http://exslt.org"))
          {
              className = getEXSLTClassName(uri);
              methodName = qname.getLocalPart();
          }
          else if (!uri.equals(ExtensionNamespaceContext.JAVA_EXT_URI))
          {
              int lastSlash = className.lastIndexOf('/');
              if (-1 != lastSlash)
                  className = className.substring(lastSlash + 1);
          }           
   
          String localPart = qname.getLocalPart();
          int lastDotIndex = localPart.lastIndexOf('.');
          if (lastDotIndex > 0)
          {
              if (className != null)
                  className = className + "." + localPart.substring(0, lastDotIndex);
              else
                  className = localPart.substring(0, lastDotIndex);
                  
              methodName = localPart.substring(lastDotIndex + 1);
          }
          else
              methodName = localPart;
       
          if(null == className || className.trim().length() == 0 
             || null == methodName || methodName.trim().length() == 0) 
              return null;
      
          ExtensionHandler handler = null;
          try
          {
              ExtensionHandler.getClassForName(className);
              handler = new ExtensionHandlerJavaClass(uri, "javaclass", className);
          }
          catch (ClassNotFoundException e)
          {
             return null;
          }
          return new XPathFunctionImpl(handler, methodName);
      }
      
      /**
       * Return the implementation class name of an EXSLT extension from
       * a given namespace uri. The uri must starts with "http://exslt.org".
       */
      private String getEXSLTClassName(String uri)
      {
          if (uri.equals(ExtensionNamespaceContext.EXSLT_MATH_URI))
              return "org.apache.xalan.lib.ExsltMath";
          else if (uri.equals(ExtensionNamespaceContext.EXSLT_SET_URI))
              return "org.apache.xalan.lib.ExsltSets";
          else if (uri.equals(ExtensionNamespaceContext.EXSLT_STRING_URI))
              return "org.apache.xalan.lib.ExsltStrings";
          else if (uri.equals(ExtensionNamespaceContext.EXSLT_DATETIME_URI))
              return "org.apache.xalan.lib.ExsltDatetime";
          else if (uri.equals(ExtensionNamespaceContext.EXSLT_DYNAMIC_URI))
              return "org.apache.xalan.lib.ExsltDynamic";
          else if (uri.equals(ExtensionNamespaceContext.EXSLT_URI))
              return "org.apache.xalan.lib.ExsltCommon";
          else
              return null;
      }
  }
  