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.transformer.TransformerImpl;
  
  /**
   * Implement xsl:fallback.
   * <pre>
   * <!ELEMENT xsl:fallback %template;>
   * <!ATTLIST xsl:fallback %space-att;>
   * </pre>
   * @see <a href="http://www.w3.org/TR/xslt#fallback">fallback in XSLT Specification</a>
   * @xsl.usage advanced
   */
  public class ElemFallback extends ElemTemplateElement
  {
      static final long serialVersionUID = 1782962139867340703L;
  
    /**
     * 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_FALLBACK;
    }
  
    /**
     * Return the node name.
     *
     * @return The Element's name
     */
    public String getNodeName()
    {
      return Constants.ELEMNAME_FALLBACK_STRING;
    }
  
    /**
     * This is the normal call when xsl:fallback is instantiated.
     * In accordance with the XSLT 1.0 Recommendation, chapter 15,
     * "Normally, instantiating an xsl:fallback element does nothing."
     *
     * @param transformer non-null reference to the the current transform-time state.
     *
     * @throws TransformerException
     */
    public void execute(
            TransformerImpl transformer)
              throws TransformerException
    {
    }
  
    /**
     * Execute the fallback elements.  This must be explicitly called to
     * instantiate the content of an xsl:fallback element.
     * When an XSLT transformer performs fallback for an instruction
     * element, if the instruction element has one or more xsl:fallback
     * children, then the content of each of the xsl:fallback children
     * must be instantiated in sequence; otherwise, an error must
     * be signaled. The content of an xsl:fallback element is a template.
     *
     * @param transformer non-null reference to the the current transform-time state.
     *
     * @throws TransformerException
     */
    public void executeFallback(
            TransformerImpl transformer)
              throws TransformerException
    {
  
      int parentElemType = m_parentNode.getXSLToken();
      if (Constants.ELEMNAME_EXTENSIONCALL == parentElemType 
          || Constants.ELEMNAME_UNDEFINED == parentElemType)
      {
  
        if (transformer.getDebug())
          transformer.getTraceManager().fireTraceEvent(this);
  
        transformer.executeChildTemplates(this, true);
  
        if (transformer.getDebug())
  	    transformer.getTraceManager().fireTraceEndEvent(this); 
      }
      else
      {
  
        // Should never happen
        System.out.println(
          "Error!  parent of xsl:fallback must be an extension or unknown element!");
      }
    }
  }
  