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.
   */
  /*
   * $Id$
   */
  package org.apache.xalan.extensions;
  
  import java.io.IOException;
  import java.util.Vector;
  
  import javax.xml.transform.TransformerException;
  
  import org.apache.xalan.templates.ElemTemplateElement;
  import org.apache.xalan.templates.Stylesheet;
  import org.apache.xalan.transformer.TransformerImpl;
  import org.apache.xpath.functions.FuncExtFunction;
  
  /**
   * Abstract base class for handling an extension namespace for XPath.
   * Provides functions to test a function's existence and call a function.
   * Also provides functions for calling an element and testing for
   * an element's existence.
   *
   * @author Sanjiva Weerawarana (sanjiva@watson.ibm.com)
   * @xsl.usage internal
   */
  public abstract class ExtensionHandler
  {
  
    /** uri of the extension namespace */
    protected String m_namespaceUri; 
  
    /** scripting language of implementation */
    protected String m_scriptLang;
  
    /**
     * This method loads a class using the context class loader if we're
     * running under Java2 or higher.
     * 
     * @param className Name of the class to load
     */
    static Class getClassForName(String className)
        throws ClassNotFoundException
    {
      // Hack for backwards compatibility with XalanJ1 stylesheets
      if(className.equals("org.apache.xalan.xslt.extensions.Redirect")) {
        className = "org.apache.xalan.lib.Redirect";
      }
  
      return ObjectFactory.findProviderClass(
          className, ObjectFactory.findClassLoader(), true);
    }
  
    /**
     * Construct a new extension namespace handler given all the information
     * needed.
     *
     * @param namespaceUri the extension namespace URI that I'm implementing
     * @param scriptLang   language of code implementing the extension
     */
    protected ExtensionHandler(String namespaceUri, String scriptLang)
    {
      m_namespaceUri = namespaceUri;
      m_scriptLang = scriptLang;
    }
  
    /**
     * Tests whether a certain function name is known within this namespace.
     * @param function name of the function being tested
     * @return true if its known, false if not.
     */
    public abstract boolean isFunctionAvailable(String function);
  
    /**
     * Tests whether a certain element name is known within this namespace.
     * @param element Name of element to check
     * @return true if its known, false if not.
     */
    public abstract boolean isElementAvailable(String element);
  
    /**
     * Process a call to a function.
     *
     * @param funcName Function name.
     * @param args     The arguments of the function call.
     * @param methodKey A key that uniquely identifies this class and method call.
     * @param exprContext The context in which this expression is being executed.
     *
     * @return the return value of the function evaluation.
     *
     * @throws TransformerException          if parsing trouble
     */
    public abstract Object callFunction(
      String funcName, Vector args, Object methodKey,
        ExpressionContext exprContext) throws TransformerException;
  
    /**
     * Process a call to a function.
     *
     * @param extFunction The XPath extension function.
     * @param args     The arguments of the function call.
     * @param exprContext The context in which this expression is being executed.
     *
     * @return the return value of the function evaluation.
     *
     * @throws TransformerException          if parsing trouble
     */
    public abstract Object callFunction(
      FuncExtFunction extFunction, Vector args,
        ExpressionContext exprContext) throws TransformerException;
  
    /**
     * Process a call to this extension namespace via an element. As a side
     * effect, the results are sent to the TransformerImpl's result tree.
     *
     * @param localPart      Element name's local part.
     * @param element        The extension element being processed.
     * @param transformer    Handle to TransformerImpl.
     * @param stylesheetTree The compiled stylesheet tree.
     * @param methodKey      A key that uniquely identifies this class and method call.
     *
     * @throws XSLProcessorException thrown if something goes wrong
     *            while running the extension handler.
     * @throws MalformedURLException if loading trouble
     * @throws FileNotFoundException if loading trouble
     * @throws IOException           if loading trouble
     * @throws TransformerException  if parsing trouble
     */
    public abstract void processElement(
      String localPart, ElemTemplateElement element, TransformerImpl transformer,
        Stylesheet stylesheetTree, Object methodKey) throws TransformerException, IOException;
  }
  