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.templates;
  
  import javax.xml.transform.TransformerException;
  import org.apache.xalan.res.XSLMessages;
  import org.apache.xalan.res.XSLTErrorResources;
  import org.apache.xalan.transformer.TransformerImpl;
  import org.apache.xpath.XPathContext;
  
  
  /**
   * Implement an unknown element
   * @xsl.usage advanced
   */
  public class ElemUnknown extends ElemLiteralResult
  {
      static final long serialVersionUID = -4573981712648730168L;
  
    /**
     * Get an int constant identifying the type of element.
     * @see org.apache.xalan.templates.Constants
     *
     *@return The token ID for this element
     */
    public int getXSLToken()
    {
      return Constants.ELEMNAME_UNDEFINED;
    }
    
    /**
     * Execute the fallbacks when an extension is not available.
     *
     * @param transformer non-null reference to the the current transform-time state.
     *
     * @throws TransformerException
     */
    private void executeFallbacks(
            TransformerImpl transformer)
              throws TransformerException
    {
      for (ElemTemplateElement child = m_firstChild; child != null;
               child = child.m_nextSibling)
      {
        if (child.getXSLToken() == Constants.ELEMNAME_FALLBACK)
        {
          try
          {
            transformer.pushElemTemplateElement(child);
            ((ElemFallback) child).executeFallback(transformer);
          }
          finally
          {
            transformer.popElemTemplateElement();
          }
        }
      }
  
    }
    
    /**
     * Return true if this extension element has a <xsl:fallback> child element.
     *
     * @return true if this extension element has a <xsl:fallback> child element.
     */
    private boolean hasFallbackChildren()
    {
      for (ElemTemplateElement child = m_firstChild; child != null;
               child = child.m_nextSibling)
      {
        if (child.getXSLToken() == Constants.ELEMNAME_FALLBACK)
          return true;
      }
      
      return false;
    }
  
  
    /**
     * Execute an unknown element.
     * Execute fallback if fallback child exists or do nothing
     *
     * @param transformer non-null reference to the the current transform-time state.
     *
     * @throws TransformerException
     */
    public void execute(TransformerImpl transformer)
              throws TransformerException
    {
  
  
      if (transformer.getDebug())
  		transformer.getTraceManager().fireTraceEvent(this);
  
  	try {
  
  		if (hasFallbackChildren()) {
  			executeFallbacks(transformer);
  		} else {
  			// do nothing
  		}
  		
  	} catch (TransformerException e) {
  		transformer.getErrorListener().fatalError(e);
  	}
      if (transformer.getDebug())
  		transformer.getTraceManager().fireTraceEndEvent(this);
    }
  
  }
  