/*
    * 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.commons.scxml.io;
  
  import java.io.IOException;
  import java.net.URL;
  import java.text.MessageFormat;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  
  import javax.xml.parsers.DocumentBuilder;
  import javax.xml.parsers.DocumentBuilderFactory;
  import javax.xml.parsers.FactoryConfigurationError;
  import javax.xml.parsers.ParserConfigurationException;
  
  import org.apache.commons.digester.Digester;
  import org.apache.commons.digester.ExtendedBaseRules;
  import org.apache.commons.digester.NodeCreateRule;
  import org.apache.commons.digester.ObjectCreateRule;
  import org.apache.commons.digester.Rule;
  import org.apache.commons.digester.SetNextRule;
  import org.apache.commons.digester.SetPropertiesRule;
  import org.apache.commons.digester.WithDefaultsRulesWrapper;
  import org.apache.commons.logging.LogFactory;
  import org.apache.commons.scxml.PathResolver;
  import org.apache.commons.scxml.SCXMLHelper;
  import org.apache.commons.scxml.env.URLResolver;
  import org.apache.commons.scxml.model.Action;
  import org.apache.commons.scxml.model.Assign;
  import org.apache.commons.scxml.model.Cancel;
  import org.apache.commons.scxml.model.CustomAction;
  import org.apache.commons.scxml.model.Data;
  import org.apache.commons.scxml.model.Datamodel;
  import org.apache.commons.scxml.model.Else;
  import org.apache.commons.scxml.model.ElseIf;
  import org.apache.commons.scxml.model.Event;
  import org.apache.commons.scxml.model.Executable;
  import org.apache.commons.scxml.model.Exit;
  import org.apache.commons.scxml.model.ExternalContent;
  import org.apache.commons.scxml.model.Final;
  import org.apache.commons.scxml.model.Finalize;
  import org.apache.commons.scxml.model.History;
  import org.apache.commons.scxml.model.If;
  import org.apache.commons.scxml.model.Initial;
  import org.apache.commons.scxml.model.Invoke;
  import org.apache.commons.scxml.model.Log;
  import org.apache.commons.scxml.model.ModelException;
  import org.apache.commons.scxml.model.NamespacePrefixesHolder;
  import org.apache.commons.scxml.model.OnEntry;
  import org.apache.commons.scxml.model.OnExit;
  import org.apache.commons.scxml.model.Parallel;
  import org.apache.commons.scxml.model.Param;
  import org.apache.commons.scxml.model.PathResolverHolder;
  import org.apache.commons.scxml.model.SCXML;
  import org.apache.commons.scxml.model.Send;
  import org.apache.commons.scxml.model.State;
  import org.apache.commons.scxml.model.Transition;
  import org.apache.commons.scxml.model.TransitionTarget;
  import org.apache.commons.scxml.model.Var;
  import org.w3c.dom.Element;
  import org.w3c.dom.Node;
  import org.w3c.dom.NodeList;
  import org.xml.sax.Attributes;
  import org.xml.sax.ErrorHandler;
  import org.xml.sax.InputSource;
  import org.xml.sax.Locator;
  import org.xml.sax.SAXException;
  
  /**
   * <p>The SCXMLParser provides the ability to parse a SCXML document into
   * the Java object model provided in the model package.</p>
   * <p>The SCXMLParser can be used for:</p>
   * <ol>
   *  <li>Parse a SCXML file into the Commons SCXML Java object model.</li>
   *  <li>Obtain a SCXML Parser for further customization of the default
   *      ruleset.</li>
   * </ol>
   *
   * <p>If switching from {@link SCXMLDigester}, changes need to be made to
   * the SCXML documents, such as:</p>
   * <ul>
   *  <li>A &lt;parallel&gt; should not be wrapped in a &lt;state&gt; element
   *      unless otherwise necessary</li>
   *  <li>&lt;var&gt; and &lt;exit&gt; elements continue to be supported by
  *      Commons SCXML, but in the Commons SCXML namespace:
  *      <code>http://commons.apache.org/scxml</code></li>
  *  <li>&lt;event&gt; is now supported</li>
  * </ul>
  * <p>See latest version of the SCXML Working Draft for more details.</p>
  *
  * <p><b>NOTE:</b> The SCXMLParser assumes that the SCXML document to be
  * parsed is well-formed and correct. If that assumption does not hold,
  * any subsequent behavior is undefined.</p>
  *
  * @since 0.7
  */
 public final class SCXMLParser {
 
     /**
      * The SCXML namespace that this Digester is built for. Any document
      * that is intended to be parsed by this digester <b>must</b>
      * bind the SCXML elements to this namespace.
      */
     private static final String NAMESPACE_SCXML =
         "http://www.w3.org/2005/07/scxml";
 
     /**
      * The namespace that defines any custom actions defined by the Commons
      * SCXML implementation. Any document that intends to use these custom
      * actions needs to ensure that they are in the correct namespace. Use
      * of actions in this namespace makes the document non-portable across
      * implementations.
      */
     private static final String NAMESPACE_COMMONS_SCXML =
         "http://commons.apache.org/scxml";
 
     //---------------------- PUBLIC METHODS ----------------------//
     /**
      * <p>API for standalone usage where the SCXML document is a URL.</p>
      *
      * @param scxmlURL
      *            a canonical absolute URL to parse (relative URLs within the
      *            top level document are to be resovled against this URL).
      * @param errHandler
      *            The SAX ErrorHandler
      *
      * @return SCXML The SCXML object corresponding to the file argument
      *
      * @throws IOException Underlying Digester parsing threw an IOException
      * @throws SAXException Underlying Digester parsing threw a SAXException
      * @throws ModelException If the resulting document model has flaws
      *
      * @see ErrorHandler
      * @see PathResolver
      */
     public static SCXML parse(final URL scxmlURL,
             final ErrorHandler errHandler)
     throws IOException, SAXException, ModelException {
 
         if (scxmlURL == null) {
             throw new IllegalArgumentException(ERR_NULL_URL);
         }
 
         return parse(scxmlURL, errHandler, null);
 
     }
 
     /**
      * <p>API for standalone usage where the SCXML document is a URI.
      * A PathResolver must be provided.</p>
      *
      * @param pathResolver
      *            The PathResolver for this context
      * @param documentRealPath
      *            The String pointing to the absolute (real) path of the
      *            SCXML document
      * @param errHandler
      *            The SAX ErrorHandler
      *
      * @return SCXML The SCXML object corresponding to the file argument
      *
      * @throws IOException Underlying Digester parsing threw an IOException
      * @throws SAXException Underlying Digester parsing threw a SAXException
      * @throws ModelException If the resulting document model has flaws
      *
      * @see ErrorHandler
      * @see PathResolver
      */
     public static SCXML parse(final String documentRealPath,
             final ErrorHandler errHandler, final PathResolver pathResolver)
     throws IOException, SAXException, ModelException {
 
         return parse(documentRealPath, errHandler, pathResolver, null);
 
     }
 
     /**
      * <p>API for standalone usage where the SCXML document is an
      * InputSource. This method may be used when the SCXML document is
      * packaged in a Java archive, or part of a compound document
      * where the SCXML root is available as a
      * <code>org.w3c.dom.Element</code> or via a <code>java.io.Reader</code>.
      * </p>
      *
      * <p><em>Note:</em> Since there is no path resolution, the SCXML document
      * must not have external state sources.</p>
      *
      * @param documentInputSource
      *            The InputSource for the SCXML document
      * @param errHandler
      *            The SAX ErrorHandler
      *
      * @return SCXML The SCXML object corresponding to the file argument
      *
      * @throws IOException Underlying Digester parsing threw an IOException
      * @throws SAXException Underlying Digester parsing threw a SAXException
      * @throws ModelException If the resulting document model has flaws
      *
      * @see ErrorHandler
      */
     public static SCXML parse(final InputSource documentInputSource,
             final ErrorHandler errHandler)
     throws IOException, SAXException, ModelException {
 
         if (documentInputSource == null) {
             throw new IllegalArgumentException(ERR_NULL_ISRC);
         }
 
         return parse(documentInputSource, errHandler, null);
 
     }
 
     /**
      * <p>API for standalone usage where the SCXML document is a URL, and
      * the document uses custom actions.</p>
      *
      * @param scxmlURL
      *            a canonical absolute URL to parse (relative URLs within the
      *            top level document are to be resovled against this URL).
      * @param errHandler
      *            The SAX ErrorHandler
      * @param customActions
      *            The list of {@link CustomAction}s this digester
      *            instance will process, can be null or empty
      *
      * @return SCXML The SCXML object corresponding to the file argument
      *
      * @throws IOException Underlying Digester parsing threw an IOException
      * @throws SAXException Underlying Digester parsing threw a SAXException
      * @throws ModelException If the resulting document model has flaws
      *
      * @see ErrorHandler
      * @see PathResolver
      */
     public static SCXML parse(final URL scxmlURL,
             final ErrorHandler errHandler, final List customActions)
     throws IOException, SAXException, ModelException {
 
         SCXML scxml = null;
         Digester scxmlParser = SCXMLParser
                 .newInstance(null, new URLResolver(scxmlURL), customActions);
         scxmlParser.setErrorHandler(errHandler);
 
         try {
             scxml = (SCXML) scxmlParser.parse(scxmlURL.toString());
         } catch (RuntimeException rte) {
             // Intercept runtime exceptions, only to log them with a
             // sensible error message about failure in document parsing
             MessageFormat msgFormat = new MessageFormat(ERR_DOC_PARSE_FAIL);
             String errMsg = msgFormat.format(new Object[] {
                 String.valueOf(scxmlURL), rte.getMessage()
             });
             org.apache.commons.logging.Log log = LogFactory.
                 getLog(SCXMLParser.class);
             log.error(errMsg, rte);
             throw rte;
         }
 
         if (scxml != null) {
             ModelUpdater.updateSCXML(scxml);
         }
 
         return scxml;
 
     }
 
     /**
      * <p>API for standalone usage where the SCXML document is a URI.
      * A PathResolver must be provided.</p>
      *
      * @param pathResolver
      *            The PathResolver for this context
      * @param documentRealPath
      *            The String pointing to the absolute (real) path of the
      *            SCXML document
      * @param errHandler
      *            The SAX ErrorHandler
      * @param customActions
      *            The list of {@link CustomAction}s this digester
      *            instance will process, can be null or empty
      *
      * @return SCXML The SCXML object corresponding to the file argument
      *
      * @throws IOException Underlying Digester parsing threw an IOException
      * @throws SAXException Underlying Digester parsing threw a SAXException
      * @throws ModelException If the resulting document model has flaws
      *
      * @see ErrorHandler
      * @see PathResolver
      */
     public static SCXML parse(final String documentRealPath,
             final ErrorHandler errHandler, final PathResolver pathResolver,
             final List customActions)
     throws IOException, SAXException, ModelException {
 
         if (documentRealPath == null) {
             throw new IllegalArgumentException(ERR_NULL_PATH);
         }
 
         SCXML scxml = null;
         Digester scxmlParser = SCXMLParser.newInstance(null, pathResolver,
             customActions);
         scxmlParser.setErrorHandler(errHandler);
 
         try {
             scxml = (SCXML) scxmlParser.parse(documentRealPath);
         } catch (RuntimeException rte) {
             // Intercept runtime exceptions, only to log them with a
             // sensible error message about failure in document parsing
             MessageFormat msgFormat = new MessageFormat(ERR_DOC_PARSE_FAIL);
             String errMsg = msgFormat.format(new Object[] {
                 documentRealPath, rte.getMessage()
             });
             org.apache.commons.logging.Log log = LogFactory.
                 getLog(SCXMLParser.class);
             log.error(errMsg, rte);
             throw rte;
         }
 
         if (scxml != null) {
             ModelUpdater.updateSCXML(scxml);
         }
 
         return scxml;
 
     }
 
     /**
      * <p>API for standalone usage where the SCXML document is an
      * InputSource. This method may be used when the SCXML document is
      * packaged in a Java archive, or part of a compound document
      * where the SCXML root is available as a
      * <code>org.w3c.dom.Element</code> or via a <code>java.io.Reader</code>.
      * </p>
      *
      * <p><em>Note:</em> Since there is no path resolution, the SCXML document
      * must not have external state sources.</p>
      *
      * @param documentInputSource
      *            The InputSource for the SCXML document
      * @param errHandler
      *            The SAX ErrorHandler
      * @param customActions
      *            The list of {@link CustomAction}s this digester
      *            instance will process, can be null or empty
      *
      * @return SCXML The SCXML object corresponding to the file argument
      *
      * @throws IOException Underlying Digester parsing threw an IOException
      * @throws SAXException Underlying Digester parsing threw a SAXException
      * @throws ModelException If the resulting document model has flaws
      *
      * @see ErrorHandler
      */
     public static SCXML parse(final InputSource documentInputSource,
             final ErrorHandler errHandler, final List customActions)
     throws IOException, SAXException, ModelException {
 
         Digester scxmlParser = SCXMLParser.newInstance(null, null,
             customActions);
         scxmlParser.setErrorHandler(errHandler);
 
         SCXML scxml = null;
         try {
             scxml = (SCXML) scxmlParser.parse(documentInputSource);
         }  catch (RuntimeException rte) {
             // Intercept runtime exceptions, only to log them with a
             // sensible error message about failure in document parsing
             org.apache.commons.logging.Log log = LogFactory.
                 getLog(SCXMLParser.class);
             log.error(ERR_ISRC_PARSE_FAIL, rte);
             throw rte;
         }
 
         if (scxml != null) {
             ModelUpdater.updateSCXML(scxml);
         }
 
         return scxml;
 
     }
 
     /**
      * <p>Obtain a SCXML digester instance for further customization.</p>
      * <b>API Notes:</b>
      * <ul>
      *   <li>Use the digest() convenience methods if you do not
      *       need a custom digester.</li>
      *   <li>After the SCXML document is parsed by the customized digester,
      *       the object model <b>must</b> be made executor-ready by calling
      *       <code>updateSCXML(SCXML)</code> method in this class.</li>
      * </ul>
      *
      * @return Digester A newly configured SCXML digester instance
      *
      * @see SCXMLParser#updateSCXML(SCXML)
      */
     public static Digester newInstance() {
 
         return newInstance(null, null, null);
 
     }
 
     /**
      * <p>Obtain a SCXML digester instance for further customization.</p>
      * <b>API Notes:</b>
      * <ul>
      *   <li>Use the digest() convenience methods if you do not
      *       need a custom digester.</li>
      *   <li>After the SCXML document is parsed by the customized digester,
      *       the object model <b>must</b> be made executor-ready by calling
      *       <code>updateSCXML(SCXML)</code> method in this class.</li>
      * </ul>
      *
      * @param pr The PathResolver, may be null for standalone documents
      * @return Digester A newly configured SCXML digester instance
      *
      * @see SCXMLParser#updateSCXML(SCXML)
      */
     public static Digester newInstance(final PathResolver pr) {
 
         return newInstance(null, pr, null);
 
     }
 
     /**
      * <p>Obtain a SCXML digester instance for further customization.</p>
      * <b>API Notes:</b>
      * <ul>
      *   <li>Use the digest() convenience methods if you do not
      *       need a custom digester.</li>
      *   <li>After the SCXML document is parsed by the customized digester,
      *       the object model <b>must</b> be made executor-ready by calling
      *       <code>updateSCXML(SCXML)</code> method in this class.</li>
      * </ul>
      *
      * @param scxml The parent SCXML document if there is one (in case of
      *              state templates for example), null otherwise
      * @param pr The PathResolver, may be null for standalone documents
      * @return Digester A newly configured SCXML digester instance
      *
      * @see SCXMLParser#updateSCXML(SCXML)
      */
     public static Digester newInstance(final SCXML scxml,
             final PathResolver pr) {
 
         return newInstance(scxml, pr, null);
 
     }
 
     /**
      * <p>Obtain a SCXML digester instance for further customization.</p>
      * <b>API Notes:</b>
      * <ul>
      *   <li>Use the digest() convenience methods if you do not
      *       need a custom digester.</li>
      *   <li>After the SCXML document is parsed by the customized digester,
      *       the object model <b>must</b> be made executor-ready by calling
      *       <code>updateSCXML(SCXML)</code> method in this class.</li>
      * </ul>
      *
      * @param scxml The parent SCXML document if there is one (in case of
      *              state templates for example), null otherwise
      * @param pr The PathResolver, may be null for standalone documents
      * @param customActions The list of {@link CustomAction}s this digester
      *              instance will process, can be null or empty
      * @return Digester A newly configured SCXML digester instance
      *
      * @see SCXMLParser#updateSCXML(SCXML)
      */
     public static Digester newInstance(final SCXML scxml,
             final PathResolver pr, final List customActions) {
 
         Digester digester = new Digester();
         digester.setNamespaceAware(true);
         //Uncomment next line after SCXML DTD is available
         //digester.setValidating(true);
         WithDefaultsRulesWrapper rules =
             new WithDefaultsRulesWrapper(initRules(scxml, pr, customActions));
         rules.addDefault(new IgnoredElementRule());
         digester.setRules(rules);
         return digester;
     }
 
     /**
      * <p>Update the SCXML object model and make it SCXMLExecutor ready.
      * This is part of post-digester processing, and sets up the necessary
      * object references throughtout the SCXML object model for the parsed
      * document. Should be used only if a customized digester obtained
      * using the <code>newInstance()</code> methods is needed.</p>
      *
      * @param scxml The SCXML object (output from Digester)
      * @throws ModelException If the document model has flaws
      */
    public static void updateSCXML(final SCXML scxml)
    throws ModelException {
        ModelUpdater.updateSCXML(scxml);
    }
 
     //---------------------- PRIVATE CONSTANTS ----------------------//
     //// Patterns to get the digestion going, prefixed by XP_
     /** Root &lt;scxml&gt; element. */
     private static final String XP_SM = "scxml";
 
     /** &lt;state&gt; children of root &lt;scxml&gt; element. */
     private static final String XP_SM_ST = "scxml/state";
 
     /** &lt;state&gt; children of root &lt;scxml&gt; element. */
     private static final String XP_SM_PAR = "scxml/parallel";
 
     /** &lt;final&gt; children of root &lt;scxml&gt; element. */
     private static final String XP_SM_FIN = "scxml/final";
 
     //// Universal matches, prefixed by XPU_
     // State
     /** &lt;state&gt; children of &lt;state&gt; elements. */
     private static final String XPU_ST_ST = "!*/state/state";
 
     /** &lt;final&gt; children of &lt;state&gt; elements. */
     private static final String XPU_ST_FIN = "!*/state/final";
 
     /** &lt;state&gt; children of &lt;parallel&gt; elements. */
     private static final String XPU_PAR_ST = "!*/parallel/state";
 
     // Parallel
     /** &lt;parallel&gt; child of &lt;state&gt; elements. */
     private static final String XPU_ST_PAR = "!*/state/parallel";
 
     // If
     /** &lt;if&gt; element. */
     private static final String XPU_IF = "!*/if";
 
     // Executables, next three patterns useful when adding custom actions
     /** &lt;onentry&gt; element. */
     private static final String XPU_ONEN = "!*/onentry";
 
     /** &lt;onexit&gt; element. */
     private static final String XPU_ONEX = "!*/onexit";
 
     /** &lt;transition&gt; element. */
     private static final String XPU_TR = "!*/transition";
 
     /** &lt;finalize&gt; element. */
     private static final String XPU_FIN = "!*/finalize";
 
     //// Path Fragments, constants prefixed by XPF_
     // Onentries and Onexits
     /** &lt;onentry&gt; child element. */
     private static final String XPF_ONEN = "/onentry";
 
     /** &lt;onexit&gt; child element. */
     private static final String XPF_ONEX = "/onexit";
 
     // Datamodel section
     /** &lt;datamodel&gt; child element. */
     private static final String XPF_DM = "/datamodel";
 
     /** Individual &lt;data&gt; elements. */
     private static final String XPF_DATA = "/data";
 
     // Initial
     /** &lt;initial&gt; child element. */
     private static final String XPF_INI = "/initial";
 
     // Invoke, param and finalize
     /** &lt;invoke&gt; child element of &lt;state&gt;. */
     private static final String XPF_INV = "/invoke";
 
     /** &lt;param&gt; child element of &lt;invoke&gt;. */
     private static final String XPF_PRM = "/param";
 
     /** &lt;finalize&gt; child element of &lt;invoke&gt;. */
     private static final String XPF_FIN = "/finalize";
 
     // History
     /** &lt;history&gt; child element. */
     private static final String XPF_HIST = "/history";
 
     // Transition, target and exit
     /** &lt;transition&gt; child element. */
     private static final String XPF_TR = "/transition";
 
     /** &lt;exit&gt; child element, a Commons SCXML custom action. */
     private static final String XPF_EXT = "/exit";
 
     // Actions
     /** &lt;assign&gt; child element. */
     private static final String XPF_ASN = "/assign";
 
     /** &lt;event&gt; child element. */
     private static final String XPF_EVT = "/event";
 
     /** &lt;send&gt; child element. */
     private static final String XPF_SND = "/send";
 
     /** &lt;cancel&gt; child element. */
     private static final String XPF_CAN = "/cancel";
 
     /** &lt;elseif&gt; child element. */
     private static final String XPF_EIF = "/elseif";
 
     /** &lt;else&gt; child element. */
     private static final String XPF_ELS = "/else";
 
     // Custom Commons SCXML actions
     /** &lt;var&gt; child element. */
     private static final String XPF_VAR = "/var";
 
     /** &lt;log&gt; child element. */
     private static final String XPF_LOG = "/log";
 
     //// Other constants
     // Error messages
     /**
      * Null URL passed as argument.
      */
     private static final String ERR_NULL_URL = "Cannot parse null URL";
 
     /**
      * Null path passed as argument.
      */
     private static final String ERR_NULL_PATH = "Cannot parse null URL";
 
     /**
      * Null InputSource passed as argument.
      */
     private static final String ERR_NULL_ISRC = "Cannot parse null URL";
 
     /**
      * Parsing SCXML document has failed.
      */
     private static final String ERR_DOC_PARSE_FAIL = "Error parsing "
         + "SCXML document: \"{0}\", with message: \"{1}\"\n";
 
     /**
      * Parsing SCXML document InputSource has failed.
      */
     private static final String ERR_ISRC_PARSE_FAIL =
         "Could not parse SCXML InputSource";
 
     /**
      * Parser configuration error while registering data rule.
      */
     private static final String ERR_PARSER_CFG_DATA = "XML Parser "
         + "misconfiguration, error registering <data> element rule";
 
     /**
      * Parser configuration error while registering send rule.
      */
     private static final String ERR_PARSER_CFG_SEND = "XML Parser "
         + "misconfiguration, error registering <send> element rule";
 
     /**
      * Parser configuration error while registering body content rule for
      * custom action.
      */
     private static final String ERR_PARSER_CFG_CUSTOM = "XML Parser "
         + "misconfiguration, error registering custom action rules";
 
     /**
      * Error message while attempting to define a custom action which does
      * not extend the Commons SCXML Action base class.
      */
     private static final String ERR_CUSTOM_ACTION_TYPE = "Custom actions list"
         + " contained unknown object (not a Commons SCXML Action subtype)";
 
     /**
      * Error message when the URI in a &lt;state&gt;'s &quot;src&quot;
      * attribute does not point to a valid SCXML document, and thus cannot be
      * parsed.
      */
     private static final String ERR_STATE_SRC =
         "Source attribute in <state src=\"{0}\"> cannot be parsed";
 
     /**
      * Error message when the target of the URI fragment in a &lt;state&gt;'s
      * &quot;src&quot; attribute is not defined in the referenced document.
      */
     private static final String ERR_STATE_SRC_FRAGMENT = "URI Fragment in "
         + "<state src=\"{0}\"> is an unknown state in referenced document";
 
     /**
      * Error message when the target of the URI fragment in a &lt;state&gt;'s
      * &quot;src&quot; attribute is not a &lt;state&gt; or &lt;final&gt; in
      * the referenced document.
      */
     private static final String ERR_STATE_SRC_FRAGMENT_TARGET = "URI Fragment"
         + " in <state src=\"{0}\"> does not point to a <state> or <final>";
 
     // String constants
     /** Slash. */
     private static final String STR_SLASH = "/";
 
     //---------------------- PRIVATE UTILITY METHODS ----------------------//
     /*
      * Private utility functions for configuring digester rule base for SCXML.
      */
     /**
      * Initialize the Digester rules for the current document.
      *
      * @param scxml The parent SCXML document (or null)
      * @param pr The PathResolver
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      *
      * @return scxmlRules The rule set to be used for digestion
      */
     private static ExtendedBaseRules initRules(final SCXML scxml,
             final PathResolver pr, final List customActions) {
 
         ExtendedBaseRules scxmlRules = new ExtendedBaseRules();
         scxmlRules.setNamespaceURI(NAMESPACE_SCXML);
 
         //// SCXML
         scxmlRules.add(XP_SM, new ObjectCreateRule(SCXML.class));
         scxmlRules.add(XP_SM, new SetPropertiesRule());
         scxmlRules.add(XP_SM, new SetCurrentNamespacesRule());
 
         //// Datamodel at document root i.e. <scxml> datamodel
         addDatamodelRules(XP_SM + XPF_DM, scxmlRules, scxml, pr);
 
         //// States
         // Level one states
         addStateRules(XP_SM_ST, scxmlRules, customActions, scxml, pr);
 
         // Nested states
         addStateRules(XPU_ST_ST, scxmlRules, customActions, scxml, pr);
 
         // Orthogonal states
         addStateRules(XPU_PAR_ST, scxmlRules, customActions, scxml, pr);
 
         //// Parallels
         // Level one parallels
         addParallelRules(XP_SM_PAR, scxmlRules, customActions, scxml, pr);
 
         // Parallel children of composite states
         addParallelRules(XPU_ST_PAR, scxmlRules, customActions, scxml, pr);
 
         //// Finals
         // Level one finals
         addFinalRules(XP_SM_FIN, scxmlRules, customActions, scxml, pr);
 
         // Final children of composite states
         addFinalRules(XPU_ST_FIN, scxmlRules, customActions, scxml, pr);
 
         //// Ifs
         addIfRules(XPU_IF, scxmlRules, pr, customActions);
 
         //// Custom actions
         addCustomActionRules(XPU_ONEN, scxmlRules, customActions);
         addCustomActionRules(XPU_ONEX, scxmlRules, customActions);
         addCustomActionRules(XPU_TR, scxmlRules, customActions);
         addCustomActionRules(XPU_IF, scxmlRules, customActions);
         addCustomActionRules(XPU_FIN, scxmlRules, customActions);
 
         return scxmlRules;
 
     }
 
     /**
      * Add Digester rules for all &lt;state&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param scxml The parent SCXML document (or null)
      * @param pr The PathResolver
      */
     private static void addStateRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final SCXML scxml, final PathResolver pr) {
         scxmlRules.add(xp, new ObjectCreateRule(State.class));
         addStatePropertiesRules(xp, scxmlRules, customActions, pr, scxml);
         addDatamodelRules(xp + XPF_DM, scxmlRules, scxml, pr);
         addInvokeRules(xp + XPF_INV, scxmlRules, customActions, pr, scxml);
         addInitialRules(xp + XPF_INI, scxmlRules, customActions, pr, scxml);
         addHistoryRules(xp + XPF_HIST, scxmlRules, customActions, pr, scxml);
         addTransitionRules(xp + XPF_TR, scxmlRules, "addTransition",
             pr, customActions);
         addHandlerRules(xp, scxmlRules, pr, customActions);
         scxmlRules.add(xp, new UpdateModelRule(scxml));
         scxmlRules.add(xp, new SetNextRule("addChild"));
     }
 
     /**
      * Add Digester rules for all &lt;parallel&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param pr The {@link PathResolver} for this document
      * @param scxml The parent SCXML document (or null)
      */
     private static void addParallelRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final SCXML scxml, final PathResolver pr) {
         addSimpleRulesTuple(xp, scxmlRules, Parallel.class, null, null,
                 "addChild");
         addDatamodelRules(xp + XPF_DM, scxmlRules, scxml, pr);
         addTransitionRules(xp + XPF_TR, scxmlRules, "addTransition",
             pr, customActions);
         addHandlerRules(xp, scxmlRules, pr, customActions);
         scxmlRules.add(xp, new UpdateModelRule(scxml));
     }
 
     /**
      * Add Digester rules for all &lt;final&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param scxml The parent SCXML document (or null)
      * @param pr The {@link PathResolver} for this document
      */
     private static void addFinalRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final SCXML scxml, final PathResolver pr) {
         addSimpleRulesTuple(xp, scxmlRules, Final.class, null, null,
             "addChild");
         addHandlerRules(xp, scxmlRules, pr, customActions);
         scxmlRules.add(xp, new UpdateModelRule(scxml));
     }
 
     /**
      * Add Digester rules for all &lt;state&gt; element attributes.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param pr The PathResolver
      * @param scxml The root document, if this one is src'ed in
      */
     private static void addStatePropertiesRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final PathResolver pr, final SCXML scxml) {
         scxmlRules.add(xp, new SetPropertiesRule(
                 new String[] {"id", "final", "initial"},
                 new String[] {"id", "final", "first"}));
         scxmlRules.add(xp, new DigestSrcAttributeRule(scxml,
             customActions, pr));
     }
 
     /**
      * Add Digester rules for all &lt;datamodel&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param pr The PathResolver
      * @param scxml The parent SCXML document (or null)
      */
     private static void addDatamodelRules(final String xp,
             final ExtendedBaseRules scxmlRules, final SCXML scxml,
             final PathResolver pr) {
         scxmlRules.add(xp, new ObjectCreateRule(Datamodel.class));
         scxmlRules.add(xp + XPF_DATA, new ObjectCreateRule(Data.class));
         scxmlRules.add(xp + XPF_DATA, new SetPropertiesRule());
         scxmlRules.add(xp + XPF_DATA, new SetCurrentNamespacesRule());
         scxmlRules.add(xp + XPF_DATA, new SetNextRule("addData"));
         try {
             scxmlRules.add(xp + XPF_DATA, new ParseDataRule(pr));
         } catch (ParserConfigurationException pce) {
             org.apache.commons.logging.Log log = LogFactory.
                 getLog(SCXMLParser.class);
             log.error(ERR_PARSER_CFG_DATA, pce);
         }
         scxmlRules.add(xp, new SetNextRule("setDatamodel"));
     }
 
     /**
      * Add Digester rules for all &lt;invoke&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of {@link CustomAction}s this digester
      *              instance will process, can be null or empty
      * @param pr The PathResolver
      * @param scxml The parent SCXML document (or null)
      */
     private static void addInvokeRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final PathResolver pr, final SCXML scxml) {
         scxmlRules.add(xp, new ObjectCreateRule(Invoke.class));
         scxmlRules.add(xp, new SetPropertiesRule());
         scxmlRules.add(xp, new SetCurrentNamespacesRule());
         scxmlRules.add(xp, new SetPathResolverRule(pr));
         scxmlRules.add(xp + XPF_PRM, new ObjectCreateRule(Param.class));
         scxmlRules.add(xp + XPF_PRM, new SetPropertiesRule());
         scxmlRules.add(xp + XPF_PRM, new SetCurrentNamespacesRule());
         scxmlRules.add(xp + XPF_PRM, new SetNextRule("addParam"));
         scxmlRules.add(xp + XPF_FIN, new ObjectCreateRule(Finalize.class));
         scxmlRules.add(xp + XPF_FIN, new UpdateFinalizeRule());
         addActionRules(xp + XPF_FIN, scxmlRules, pr, customActions);
         scxmlRules.add(xp + XPF_FIN, new SetNextRule("setFinalize"));
         scxmlRules.add(xp, new SetNextRule("setInvoke"));
     }
 
     /**
      * Add Digester rules for all &lt;initial&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param pr The PathResolver
      * @param scxml The parent SCXML document (or null)
      */
     private static void addInitialRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final PathResolver pr, final SCXML scxml) {
         scxmlRules.add(xp, new ObjectCreateRule(Initial.class));
         addPseudoStatePropertiesRules(xp, scxmlRules, customActions, pr,
             scxml);
         scxmlRules.add(xp, new UpdateModelRule(scxml));
         addTransitionRules(xp + XPF_TR, scxmlRules, "setTransition",
             pr, customActions);
         scxmlRules.add(xp, new SetNextRule("setInitial"));
     }
 
     /**
      * Add Digester rules for all &lt;history&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param pr The PathResolver
      * @param scxml The parent SCXML document (or null)
      */
     private static void addHistoryRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final PathResolver pr, final SCXML scxml) {
         scxmlRules.add(xp, new ObjectCreateRule(History.class));
         addPseudoStatePropertiesRules(xp, scxmlRules, customActions, pr,
             scxml);
         scxmlRules.add(xp, new UpdateModelRule(scxml));
         scxmlRules.add(xp, new SetPropertiesRule(new String[] {"type"},
             new String[] {"type"}));
         addTransitionRules(xp + XPF_TR, scxmlRules, "setTransition",
             pr, customActions);
         scxmlRules.add(xp, new SetNextRule("addHistory"));
     }
 
     /**
      * Add Digester rules for all pseudo state (initial, history) element
      * attributes.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      * @param pr The PathResolver
      * @param scxml The root document, if this one is src'ed in
      */
     private static void addPseudoStatePropertiesRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions,
             final PathResolver pr, final SCXML scxml) {
         scxmlRules.add(xp, new SetPropertiesRule(new String[] {"id"},
             new String[] {"id"}));
         scxmlRules.add(xp, new DigestSrcAttributeRule(scxml, customActions,
             pr));
     }
 
     /**
      * Add Digester rules for all &lt;transition&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param setNextMethod The method name for adding this transition
      *             to its parent (defined by the SCXML Java object model).
      * @param pr The {@link PathResolver} for this document
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      */
     private static void addTransitionRules(final String xp,
             final ExtendedBaseRules scxmlRules, final String setNextMethod,
             final PathResolver pr, final List customActions) {
         scxmlRules.add(xp, new ObjectCreateRule(Transition.class));
         scxmlRules.add(xp, new SetPropertiesRule(
             new String[] {"event", "cond", "target"},
             new String[] {"event", "cond", "next"}));
         scxmlRules.add(xp, new SetCurrentNamespacesRule());
         addActionRules(xp, scxmlRules, pr, customActions);
 
         // Add <exit> custom action rule in Commons SCXML namespace
         scxmlRules.setNamespaceURI(NAMESPACE_COMMONS_SCXML);
         scxmlRules.add(xp + XPF_EXT, new Rule() {
             public void end(final String namespace, final String name) {
                 Transition t = (Transition) getDigester().peek(1);
                 TransitionTarget tt = (TransitionTarget) getDigester().
                     peek(2);
                 if (tt instanceof Initial) {
                     org.apache.commons.logging.Log log = LogFactory.
                         getLog(SCXMLParser.class);
                     log.warn("Ignored <exit> action in <initial>");
                 } else {
                     State exitState = new State();
                     exitState.setFinal(true);
                     t.getTargets().add(exitState);
                 }
             }
         });
         scxmlRules.setNamespaceURI(NAMESPACE_SCXML);
 
         scxmlRules.add(xp, new SetNextRule(setNextMethod));
     }
 
     /**
      * Add Digester rules for all &lt;onentry&gt; and &lt;onexit&gt;
      * elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param pr The {@link PathResolver} for this document
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      */
     private static void addHandlerRules(final String xp,
             final ExtendedBaseRules scxmlRules, final PathResolver pr,
             final List customActions) {
         scxmlRules.add(xp + XPF_ONEN, new ObjectCreateRule(OnEntry.class));
         addActionRules(xp + XPF_ONEN, scxmlRules, pr, customActions);
         scxmlRules.add(xp + XPF_ONEN, new SetNextRule("setOnEntry"));
         scxmlRules.add(xp + XPF_ONEX, new ObjectCreateRule(OnExit.class));
         addActionRules(xp + XPF_ONEX, scxmlRules, pr, customActions);
         scxmlRules.add(xp + XPF_ONEX, new SetNextRule("setOnExit"));
     }
 
     /**
      * Add Digester rules for all actions (&quot;executable&quot; elements).
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param pr The {@link PathResolver} for this document
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      */
     private static void addActionRules(final String xp,
             final ExtendedBaseRules scxmlRules, final PathResolver pr,
             final List customActions) {
         // Actions in SCXML namespace
         addActionRulesTuple(xp + XPF_ASN, scxmlRules, Assign.class);
         scxmlRules.add(xp + XPF_ASN, new SetPathResolverRule(pr));
         addActionRulesTuple(xp + XPF_EVT, scxmlRules, Event.class);
         addSendRulesTuple(xp + XPF_SND, scxmlRules);
         addActionRulesTuple(xp + XPF_CAN, scxmlRules, Cancel.class);
         addActionRulesTuple(xp + XPF_LOG, scxmlRules, Log.class);
 
         // Actions in Commons SCXML namespace
         scxmlRules.setNamespaceURI(NAMESPACE_COMMONS_SCXML);
 
         addActionRulesTuple(xp + XPF_VAR, scxmlRules, Var.class);
         addActionRulesTuple(xp + XPF_EXT, scxmlRules, Exit.class);
 
         // Reset namespace
         scxmlRules.setNamespaceURI(NAMESPACE_SCXML);
     }
 
     /**
      * Add custom action rules, if any custom actions are provided.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      */
     private static void addCustomActionRules(final String xp,
             final ExtendedBaseRules scxmlRules, final List customActions) {
         if (customActions == null || customActions.size() == 0) {
             return;
         }
         for (int i = 0; i < customActions.size(); i++) {
             Object item = customActions.get(i);
             if (item == null || !(item instanceof CustomAction)) {
                 org.apache.commons.logging.Log log = LogFactory.
                     getLog(SCXMLParser.class);
                 log.warn(ERR_CUSTOM_ACTION_TYPE);
             } else {
                 CustomAction ca = (CustomAction) item;
                 scxmlRules.setNamespaceURI(ca.getNamespaceURI());
                 String xpfLocalName = STR_SLASH + ca.getLocalName();
                 Class klass = ca.getActionClass();
                 if (SCXMLHelper.implementationOf(klass,
                         ExternalContent.class)) {
                     addCustomActionRulesTuple(xp + xpfLocalName, scxmlRules,
                         klass, true);
                 } else {
                     addCustomActionRulesTuple(xp + xpfLocalName, scxmlRules,
                         klass, false);
                 }
             }
         }
         scxmlRules.setNamespaceURI(NAMESPACE_SCXML);
     }
 
     /**
      * Add Digester rules that are specific to the &lt;send&gt; action
      * element.
      *
      * @param xp The Digester style XPath expression of &lt;send&gt; element
      * @param scxmlRules The rule set to be used for digestion
      */
     private static void addSendRulesTuple(final String xp,
             final ExtendedBaseRules scxmlRules) {
         addActionRulesTuple(xp, scxmlRules, Send.class);
         try {
             scxmlRules.add(xp, new ParseExternalContentRule());
         } catch (ParserConfigurationException pce) {
             org.apache.commons.logging.Log log = LogFactory.
                 getLog(SCXMLParser.class);
             log.error(ERR_PARSER_CFG_SEND, pce);
         }
     }
 
     /**
      * Add Digester rules for a simple custom action (no body content).
      *
      * @param xp The path to the custom action element
      * @param scxmlRules The rule set to be used for digestion
      * @param klass The <code>Action</code> class implementing the custom
      *              action.
      * @param bodyContent Whether the custom rule has body content
      *              that should be parsed using
      *              <code>NodeCreateRule</code>
      */
     private static void addCustomActionRulesTuple(final String xp,
             final ExtendedBaseRules scxmlRules, final Class klass,
             final boolean bodyContent) {
         addActionRulesTuple(xp, scxmlRules, klass);
         if (bodyContent) {
             try {
                 scxmlRules.add(xp, new ParseExternalContentRule());
             } catch (ParserConfigurationException pce) {
                 org.apache.commons.logging.Log log = LogFactory.
                     getLog(SCXMLParser.class);
                 log.error(ERR_PARSER_CFG_CUSTOM, pce);
             }
         }
     }
 
     /**
      * Add Digester rules for all &lt;if&gt; elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param pr The {@link PathResolver} for this document
      * @param customActions The list of custom actions this digester needs
      *                      to be able to process
      */
     private static void addIfRules(final String xp,
             final ExtendedBaseRules scxmlRules, final PathResolver pr,
             final List customActions) {
         addActionRulesTuple(xp, scxmlRules, If.class);
         addActionRules(xp, scxmlRules, pr, customActions);
         addActionRulesTuple(xp + XPF_EIF, scxmlRules, ElseIf.class);
         addActionRulesTuple(xp + XPF_ELS, scxmlRules, Else.class);
     }
 
     /**
      * Add Digester rules that are common across all actions elements.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param klass The class in the Java object model to be instantiated
      *              in the ObjectCreateRule for this action
      */
     private static void addActionRulesTuple(final String xp,
             final ExtendedBaseRules scxmlRules, final Class klass) {
         addSimpleRulesTuple(xp, scxmlRules, klass, null, null, "addAction");
         scxmlRules.add(xp, new SetExecutableParentRule());
         scxmlRules.add(xp, new SetCurrentNamespacesRule());
     }
 
     /**
      * Add the run of the mill Digester rules for any element.
      *
      * @param xp The Digester style XPath expression of the parent
      *           XML element
      * @param scxmlRules The rule set to be used for digestion
      * @param klass The class in the Java object model to be instantiated
      *              in the ObjectCreateRule for this action
      * @param args The attributes to be mapped into the object model
      * @param props The properties that args get mapped to
      * @param addMethod The method that the SetNextRule should call
      */
     private static void addSimpleRulesTuple(final String xp,
             final ExtendedBaseRules scxmlRules, final Class klass,
             final String[] args, final String[] props,
             final String addMethod) {
         scxmlRules.add(xp, new ObjectCreateRule(klass));
         if (args == null) {
             scxmlRules.add(xp, new SetPropertiesRule());
         } else {
             scxmlRules.add(xp, new SetPropertiesRule(args, props));
         }
         scxmlRules.add(xp, new SetNextRule(addMethod));
     }
 
     /**
      * Discourage instantiation since this is a utility class.
      */
     private SCXMLParser() {
         super();
     }
 
     /**
      * Custom digestion rule for establishing necessary associations of this
      * TransitionTarget with the root SCXML object.
      * These include: <br>
      * 1) Updation of the SCXML object's global targets Map <br>
      * 2) Obtaining a handle to the SCXML object's NotificationRegistry <br>
      */
     private static class UpdateModelRule extends Rule {
 
         /**
          * The root SCXML object.
          */
         private SCXML scxml;
 
         /**
          * Constructor.
          * @param scxml The root SCXML object
          */
         UpdateModelRule(final SCXML scxml) {
             super();
             this.scxml = scxml;
         }
 
         /**
          * @see Rule#end(String, String)
          */
         public final void end(final String namespace, final String name) {
             if (scxml == null) {
                 scxml = (SCXML) getDigester()
                         .peek(getDigester().getCount() - 1);
             }
             TransitionTarget tt = (TransitionTarget) getDigester().peek();
             scxml.addTarget(tt);
         }
     }
 
     /**
      * Custom digestion rule for setting Executable parent of Action elements.
      */
     private static class SetExecutableParentRule extends Rule {
 
         /**
          * Constructor.
          */
         SetExecutableParentRule() {
             super();
         }
 
         /**
          * @see Rule#end(String, String)
          */
         public final void end(final String namespace, final String name) {
             Action child = (Action) getDigester().peek();
             for (int i = 1; i < getDigester().getCount() - 1; i++) {
                 Object ancestor = getDigester().peek(i);
                 if (ancestor instanceof Executable) {
                     child.setParent((Executable) ancestor);
                     return;
                 }
             }
         }
     }
 
     /**
      * Custom digestion rule for parsing bodies of
      * <code>ExternalContent</code> elements.
      *
      * @see ExternalContent
      */
     private static class ParseExternalContentRule extends NodeCreateRule {
         /**
          * Constructor.
          * @throws ParserConfigurationException A JAXP configuration error
          */
         ParseExternalContentRule()
         throws ParserConfigurationException {
             super();
         }
         /**
          * @see Rule#end(String, String)
          */
         public final void end(final String namespace, final String name) {
             Element bodyElement = (Element) getDigester().pop();
             NodeList childNodes = bodyElement.getChildNodes();
             List externalNodes = ((ExternalContent) getDigester().
                 peek()).getExternalNodes();
             for (int i = 0; i < childNodes.getLength(); i++) {
                 externalNodes.add(childNodes.item(i));
             }
         }
     }
 
     /**
      * Custom digestion rule for parsing bodies of &lt;data&gt; elements.
      */
     private static class ParseDataRule extends NodeCreateRule {
 
         /**
          * The PathResolver used to resolve the src attribute to the
          * SCXML document it points to.
          * @see PathResolver
          */
         private PathResolver pr;
 
         /**
          * The "src" attribute, retained to check if body content is legal.
          */
         private String src;
 
         /**
          * The "expr" attribute, retained to check if body content is legal.
          */
         private String expr;
 
         /**
          * The XML tree for this data, parse as a Node, obtained from
          * either the "src" or the "expr" attributes.
          */
         private Node attrNode;
 
         /**
          * Constructor.
          *
          * @param pr The <code>PathResolver</code>
          * @throws ParserConfigurationException A JAXP configuration error
          */
         ParseDataRule(final PathResolver pr)
         throws ParserConfigurationException {
             super();
             this.pr = pr;
         }
 
         /**
          * @see Rule#begin(String, String, Attributes)
          */
         public final void begin(final String namespace, final String name,
                 final Attributes attributes) throws Exception {
             super.begin(namespace, name, attributes);
             src = attributes.getValue("src");
             expr = attributes.getValue("expr");
             if (!SCXMLHelper.isStringEmpty(src)) {
                 String path = null;
                 if (pr == null) {
                     path = src;
                 } else {
                     path = pr.resolvePath(src);
                 }
                 try {
                     DocumentBuilderFactory dbFactory = DocumentBuilderFactory.
                         newInstance();
                     DocumentBuilder db = dbFactory.newDocumentBuilder();
                     attrNode = db.parse(path);
                 } catch (FactoryConfigurationError t) {
                     logError(t);
                 } catch (ParserConfigurationException t) {
                     logError(t);
                 } catch (SAXException t) {
                     logError(t);
                 } catch (IOException t) {
                     logError(t);
                 }
                 return;
             }
         }
 
         /**
          * @param throwable
          */
         private void logError(Throwable throwable) {
             org.apache.commons.logging.Log log = LogFactory.getLog(SCXMLParser.class);
             log.error(throwable.getMessage(), throwable);
         }
 
         /**
          * @see Rule#end(String, String)
          */
         public final void end(final String namespace, final String name) {
             Node bodyNode = (Node) getDigester().pop();
             Data data = ((Data) getDigester().peek());
             // Prefer "src" over "expr", "expr" over child nodes
             // "expr" can only be evaluated at execution time
             if (!SCXMLHelper.isStringEmpty(src)) {
                 data.setNode(attrNode);
             } else  if (SCXMLHelper.isStringEmpty(expr)) {
                 // both "src" and "expr" are empty
                 data.setNode(bodyNode);
             }
         }
     }
 
     /**
      * Custom digestion rule for external sources, that is, the src attribute of
      * the &lt;state&gt; element.
      */
     private static class DigestSrcAttributeRule extends Rule {
 
         /**
          * The PathResolver used to resolve the src attribute to the
          * SCXML document it points to.
          * @see PathResolver
          */
         private PathResolver pr;
 
         /**
          * The root document.
          */
         private SCXML root;
 
         /**
          * The list of custom actions the parent document is capable of
          * processing (and hence, the child should be, by transitivity).
          * @see CustomAction
          */
         private List customActions;
 
         /**
          * Constructor.
          * @param pr The PathResolver
          * @param customActions The list of custom actions this digester needs
          *                      to be able to process
          *
          * @see PathResolver
          * @see CustomAction
          */
         DigestSrcAttributeRule(final List customActions,
                 final PathResolver pr) {
             super();
             this.customActions = customActions;
             this.pr = pr;
         }
 
         /**
          * Constructor.
          * @param root The root document, if this one is src'ed in
          * @param pr The PathResolver
          * @param customActions The list of custom actions this digester needs
          *                      to be able to process
          *
          * @see PathResolver
          * @see CustomAction
          */
         DigestSrcAttributeRule(final SCXML root,
                 final List customActions, final PathResolver pr) {
             super();
             this.root = root;
             this.customActions = customActions;
             this.pr = pr;
         }
 
         /**
          * @see Rule#begin(String, String, Attributes)
          */
         public final void begin(final String namespace, final String name,
                 final Attributes attributes) throws ModelException {
             String src = attributes.getValue("src");
             if (SCXMLHelper.isStringEmpty(src)) {
                 return;
             }
 
             // 1) Digest the external SCXML file
             Digester digester = getDigester();
             SCXML scxml = (SCXML) digester.peek(digester.getCount() - 1);
             SCXML parent = root;
             if (parent == null) {
                 parent = scxml;
             }
             String path;
             PathResolver nextpr = null;
             if (pr == null) {
                 path = src;
             } else {
                 path = pr.resolvePath(src);
                 nextpr = pr.getResolver(src);
             }
             String[] fragments = path.split("#", 2);
             String location = fragments[0];
             String fragment = null;
             if (fragments.length > 1) {
                 fragment = fragments[1];
             }
             Digester externalSrcDigester;
             if (fragment != null) {
                 // Cannot pull in all targets just yet, i.e. null parent
                 externalSrcDigester = newInstance(null, nextpr,
                     customActions);
             } else {
                 externalSrcDigester = newInstance(parent, nextpr,
                     customActions);
             }
             SCXML externalSCXML = null;
             try {
                 externalSCXML = (SCXML) externalSrcDigester.parse(location);
             } catch (Exception e) {
                 MessageFormat msgFormat =
                     new MessageFormat(ERR_STATE_SRC);
                 String errMsg = msgFormat.format(new Object[] {
                     path
                 });
                 throw new ModelException(errMsg + " : " + e.getMessage(), e);
             }
 
             // 2) Adopt the children and datamodel
             if (externalSCXML == null) {
                 return;
             }
             State s = (State) digester.peek();
             if (fragment == null) {
                 // All targets pulled in since its not a src fragment
                 Initial ini = new Initial();
                 Transition t = new Transition();
                 t.setNext(externalSCXML.getInitial());
                 ini.setTransition(t);
                 s.setInitial(ini);
                 Map children = externalSCXML.getChildren();
                 Iterator childIter = children.values().iterator();
                 while (childIter.hasNext()) {
                     s.addChild((TransitionTarget) childIter.next());
                 }
                 s.setDatamodel(externalSCXML.getDatamodel());
             } else {
                 // Need to pull in descendent targets
                 Object source = externalSCXML.getTargets().get(fragment);
                 if (source == null) {
                     MessageFormat msgFormat =
                         new MessageFormat(ERR_STATE_SRC_FRAGMENT);
                     String errMsg = msgFormat.format(new Object[] {
                         path
                     });
                     throw new ModelException(errMsg);
                 }
                 if (source instanceof State) {
                     State include = (State) source;
                     s.setOnEntry(include.getOnEntry());
                     s.setOnExit(include.getOnExit());
                     s.setDatamodel(include.getDatamodel());
                     List histories = include.getHistory();
                     for (int i = 0; i < histories.size(); i++) {
                         History h = (History) histories.get(i);
                         s.addHistory(h);
                         parent.addTarget(h);
                     }
                     Iterator childIter = include.getChildren().values().iterator();
                     while (childIter.hasNext()) {
                         TransitionTarget tt = (TransitionTarget) childIter.next();
                         s.addChild(tt);
                         parent.addTarget(tt);
                         addTargets(parent, tt);
                     }
                     s.setInvoke(include.getInvoke());
                     s.setFinal(include.isFinal());
                     if (include.getInitial() != null) {
                         s.setInitial(include.getInitial());
                     }
                     Iterator transIter = include.getTransitionsList().iterator();
                     while (transIter.hasNext()) {
                         s.addTransition((Transition) transIter.next());
                     }
                 } else {
                     MessageFormat msgFormat =
                         new MessageFormat(ERR_STATE_SRC_FRAGMENT_TARGET);
                     String errMsg = msgFormat.format(new Object[] {
                         path
                     });
                     throw new ModelException(errMsg);
                 }
             }
         }
 
         /**
          * Add all the nested targets from given target to given parent state machine.
          *
          * @param parent The state machine
          * @param tt The transition target to import
          */
         private static void addTargets(final SCXML parent, final TransitionTarget tt) {
             Iterator histIter = tt.getHistory().iterator();
             while (histIter.hasNext()) {
                 History h = (History) histIter.next();
                 parent.addTarget(h);
             }
             if (tt instanceof State) {
                 Iterator childIter = ((State) tt).getChildren().values().iterator();
                 while (childIter.hasNext()) {
                     TransitionTarget child = (TransitionTarget) childIter.next();
                     parent.addTarget(child);
                     addTargets(parent, child);
                 }
             } else if (tt instanceof Parallel) {
                 Iterator childIter = ((Parallel) tt).getChildren().iterator();
                 while (childIter.hasNext()) {
                     TransitionTarget child = (TransitionTarget) childIter.next();
                     parent.addTarget(child);
                     addTargets(parent, child);
                 }
             }
         }
     }
 
     /**
      * Custom digestion rule for setting PathResolver for runtime retrieval.
      */
     private static class SetPathResolverRule extends Rule {
 
         /**
          * The PathResolver to set.
          * @see PathResolver
          */
         private PathResolver pr;
 
         /**
          * Constructor.
          * @param pr The PathResolver
          *
          * @see PathResolver
          */
         SetPathResolverRule(final PathResolver pr) {
             super();
             this.pr = pr;
         }
 
         /**
          * @see Rule#begin(String, String, Attributes)
          */
         public final void begin(final String namespace, final String name,
                 final Attributes attributes) {
             PathResolverHolder prHolder = (PathResolverHolder) getDigester().
                 peek();
             prHolder.setPathResolver(pr);
         }
     }
 
     /**
      * Custom digestion rule for setting state parent of finalize.
      */
     private static class UpdateFinalizeRule extends Rule {
 
         /**
          * @see Rule#begin(String, String, Attributes)
          */
         public final void begin(final String namespace, final String name,
                 final Attributes attributes) {
             Finalize finalize = (Finalize) getDigester().peek();
             // state/invoke/finalize --> peek(2)
             TransitionTarget tt = (TransitionTarget) getDigester().peek(2);
             finalize.setParent(tt);
         }
     }
 
 
     /**
      * Custom digestion rule for attaching a snapshot of current namespaces
      * to SCXML actions for deferred XPath evaluation.
      */
     private static class SetCurrentNamespacesRule extends Rule {
 
         /**
          * @see Rule#begin(String, String, Attributes)
          */
         public final void begin(final String namespace, final String name,
                 final Attributes attributes) {
             NamespacePrefixesHolder nsHolder =
                 (NamespacePrefixesHolder) getDigester().peek();
             nsHolder.setNamespaces(getDigester().getCurrentNamespaces());
         }
     }
 
     /**
      * Custom digestion rule logging ignored elements.
      */
     private static class IgnoredElementRule extends Rule {
 
         /**
          * @see Rule#begin(String, String, Attributes)
          */
         public final void begin(final String namespace, final String name,
                 final Attributes attributes) {
             org.apache.commons.logging.Log log = LogFactory.
                 getLog(SCXMLParser.class);
             Locator l = digester.getDocumentLocator();
             String identifier = l.getSystemId();
             if (identifier == null) {
                 identifier = l.getPublicId();
             }
             StringBuffer sb = new StringBuffer();
             sb.append("Ignoring element <").append(name).
                 append("> in namespace \"").append(namespace).
                 append("\" at ").append(identifier).append(":").
                 append(l.getLineNumber()).append(":").
                 append(l.getColumnNumber()).append(" and digester match \"").
                 append(digester.getMatch()).append("\"");
             log.warn(sb.toString());
         }
     }
 
 }