Java example source code file (TreeWalker.java)

This example Java source code file (TreeWalker.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

contenthandler, dom, dom2helper, element, entityreference, lexicalhandler, locator, locatorimpl, namednodemap, node, processinginstruction, sax, securityexception, serializationhandler, string, treewalker

The TreeWalker.java Java example source code

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * Copyright 1999-2005 The Apache Software Foundation.
 *
 * Licensed 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: TreeWalker.java,v 1.1.4.1 2005/09/08 10:58:44 suresh_emailid Exp $
 */
package com.sun.org.apache.xml.internal.serializer;

import com.sun.org.apache.xalan.internal.utils.SecuritySupport;
import java.io.File;

import com.sun.org.apache.xml.internal.serializer.utils.AttList;
import com.sun.org.apache.xml.internal.serializer.utils.DOM2Helper;
import org.w3c.dom.Comment;
import org.w3c.dom.Element;
import org.w3c.dom.EntityReference;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.ProcessingInstruction;
import org.w3c.dom.Text;

import org.xml.sax.ContentHandler;
import org.xml.sax.Locator;
import org.xml.sax.ext.LexicalHandler;
import org.xml.sax.helpers.LocatorImpl;

/**
 * This class does a pre-order walk of the DOM tree, calling a ContentHandler
 * interface as it goes.
 *
 * This class is a copy of the one in com.sun.org.apache.xml.internal.utils.
 * It exists to cut the serializers dependancy on that package.
 *
 * @xsl.usage internal
 */

public final class TreeWalker
{

  /** Local reference to a ContentHandler          */
  final private ContentHandler m_contentHandler;
  /**
   * If m_contentHandler is a SerializationHandler, then this is
   * a reference to the same object.
   */
  final private SerializationHandler m_Serializer;

  // ARGHH!!  JAXP Uses Xerces without setting the namespace processing to ON!
  // DOM2Helper m_dh = new DOM2Helper();

  /** DomHelper for this TreeWalker          */
  final protected DOM2Helper m_dh;

  /** Locator object for this TreeWalker          */
  final private LocatorImpl m_locator = new LocatorImpl();

  /**
   * Get the ContentHandler used for the tree walk.
   *
   * @return the ContentHandler used for the tree walk
   */
  public ContentHandler getContentHandler()
  {
    return m_contentHandler;
  }

  public TreeWalker(ContentHandler ch) {
      this(ch,null);
  }
  /**
   * Constructor.
   * @param   contentHandler The implemention of the
   * contentHandler operation (toXMLString, digest, ...)
   */
  public TreeWalker(ContentHandler contentHandler, String systemId)
  {
      // Set the content handler
      m_contentHandler = contentHandler;
      if (m_contentHandler instanceof SerializationHandler) {
          m_Serializer = (SerializationHandler) m_contentHandler;
      }
      else
          m_Serializer = null;

      // Set the system ID, if it is given
      m_contentHandler.setDocumentLocator(m_locator);
      if (systemId != null)
          m_locator.setSystemId(systemId);
      else {
          try {
            // Bug see Bugzilla  26741
            m_locator.setSystemId(SecuritySupport.getSystemProperty("user.dir") + File.separator + "dummy.xsl");
           }
           catch (SecurityException se) {// user.dir not accessible from applet
           }
      }

      // Set the document locator
                if (m_contentHandler != null)
                        m_contentHandler.setDocumentLocator(m_locator);
                try {
                   // Bug see Bugzilla  26741
                  m_locator.setSystemId(SecuritySupport.getSystemProperty("user.dir") + File.separator + "dummy.xsl");
                }
                catch (SecurityException se){// user.dir not accessible from applet

    }
    m_dh = new DOM2Helper();
  }

  /**
   * Perform a pre-order traversal non-recursive style.
   *
   * Note that TreeWalker assumes that the subtree is intended to represent
   * a complete (though not necessarily well-formed) document and, during a
   * traversal, startDocument and endDocument will always be issued to the
   * SAX listener.
   *
   * @param pos Node in the tree where to start traversal
   *
   * @throws TransformerException
   */
  public void traverse(Node pos) throws org.xml.sax.SAXException
  {

    this.m_contentHandler.startDocument();

    Node top = pos;

    while (null != pos)
    {
      startNode(pos);

      Node nextNode = pos.getFirstChild();

      while (null == nextNode)
      {
        endNode(pos);

        if (top.equals(pos))
          break;

        nextNode = pos.getNextSibling();

        if (null == nextNode)
        {
          pos = pos.getParentNode();

          if ((null == pos) || (top.equals(pos)))
          {
            if (null != pos)
              endNode(pos);

            nextNode = null;

            break;
          }
        }
      }

      pos = nextNode;
    }
    this.m_contentHandler.endDocument();
  }

  /**
   * Perform a pre-order traversal non-recursive style.

   * Note that TreeWalker assumes that the subtree is intended to represent
   * a complete (though not necessarily well-formed) document and, during a
   * traversal, startDocument and endDocument will always be issued to the
   * SAX listener.
   *
   * @param pos Node in the tree where to start traversal
   * @param top Node in the tree where to end traversal
   *
   * @throws TransformerException
   */
  public void traverse(Node pos, Node top) throws org.xml.sax.SAXException
  {

    this.m_contentHandler.startDocument();

    while (null != pos)
    {
      startNode(pos);

      Node nextNode = pos.getFirstChild();

      while (null == nextNode)
      {
        endNode(pos);

        if ((null != top) && top.equals(pos))
          break;

        nextNode = pos.getNextSibling();

        if (null == nextNode)
        {
          pos = pos.getParentNode();

          if ((null == pos) || ((null != top) && top.equals(pos)))
          {
            nextNode = null;

            break;
          }
        }
      }

      pos = nextNode;
    }
    this.m_contentHandler.endDocument();
  }

  /** Flag indicating whether following text to be processed is raw text          */
  boolean nextIsRaw = false;

  /**
   * Optimized dispatch of characters.
   */
  private final void dispatachChars(Node node)
     throws org.xml.sax.SAXException
  {
    if(m_Serializer != null)
    {
      this.m_Serializer.characters(node);
    }
    else
    {
      String data = ((Text) node).getData();
      this.m_contentHandler.characters(data.toCharArray(), 0, data.length());
    }
  }

  /**
   * Start processing given node
   *
   *
   * @param node Node to process
   *
   * @throws org.xml.sax.SAXException
   */
  protected void startNode(Node node) throws org.xml.sax.SAXException
  {

//   TODO: <REVIEW>
//    A Serializer implements ContentHandler, but not NodeConsumer
//    so drop this reference to NodeConsumer which would otherwise
//    pull in all sorts of things
//    if (m_contentHandler instanceof NodeConsumer)
//    {
//      ((NodeConsumer) m_contentHandler).setOriginatingNode(node);
//    }
//    TODO: </REVIEW>

                if (node instanceof Locator)
                {
                        Locator loc = (Locator)node;
                        m_locator.setColumnNumber(loc.getColumnNumber());
                        m_locator.setLineNumber(loc.getLineNumber());
                        m_locator.setPublicId(loc.getPublicId());
                        m_locator.setSystemId(loc.getSystemId());
                }
                else
                {
                        m_locator.setColumnNumber(0);
      m_locator.setLineNumber(0);
                }

    switch (node.getNodeType())
    {
    case Node.COMMENT_NODE :
    {
      String data = ((Comment) node).getData();

      if (m_contentHandler instanceof LexicalHandler)
      {
        LexicalHandler lh = ((LexicalHandler) this.m_contentHandler);

        lh.comment(data.toCharArray(), 0, data.length());
      }
    }
    break;
    case Node.DOCUMENT_FRAGMENT_NODE :

      // ??;
      break;
    case Node.DOCUMENT_NODE :

      break;
    case Node.ELEMENT_NODE :
      Element elem_node = (Element) node;
      {
          // Make sure the namespace node
          // for the element itself is declared
          // to the ContentHandler
          String uri = elem_node.getNamespaceURI();
          if (uri != null) {
              String prefix = elem_node.getPrefix();
              if (prefix==null)
                prefix="";
              this.m_contentHandler.startPrefixMapping(prefix,uri);
          }
      }
      NamedNodeMap atts = elem_node.getAttributes();
      int nAttrs = atts.getLength();
      // System.out.println("TreeWalker#startNode: "+node.getNodeName());


      // Make sure the namespace node of
      // each attribute is declared to the ContentHandler
      for (int i = 0; i < nAttrs; i++)
      {
        final Node attr = atts.item(i);
        final String attrName = attr.getNodeName();
        final int colon = attrName.indexOf(':');
        final String prefix;

        // System.out.println("TreeWalker#startNode: attr["+i+"] = "+attrName+", "+attr.getNodeValue());
        if (attrName.equals("xmlns") || attrName.startsWith("xmlns:"))
        {
          // Use "" instead of null, as Xerces likes "" for the
          // name of the default namespace.  Fix attributed
          // to "Steven Murray" <smurray@ebt.com>.
          if (colon < 0)
            prefix = "";
          else
            prefix = attrName.substring(colon + 1);

          this.m_contentHandler.startPrefixMapping(prefix,
                                                   attr.getNodeValue());
        }
        else if (colon > 0) {
            prefix = attrName.substring(0,colon);
            String uri = attr.getNamespaceURI();
            if (uri != null)
                this.m_contentHandler.startPrefixMapping(prefix,uri);
        }
      }

      String ns = m_dh.getNamespaceOfNode(node);
      if(null == ns)
        ns = "";
      this.m_contentHandler.startElement(ns,
                                         m_dh.getLocalNameOfNode(node),
                                         node.getNodeName(),
                                         new AttList(atts, m_dh));
      break;
    case Node.PROCESSING_INSTRUCTION_NODE :
    {
      ProcessingInstruction pi = (ProcessingInstruction) node;
      String name = pi.getNodeName();

      // String data = pi.getData();
      if (name.equals("xslt-next-is-raw"))
      {
        nextIsRaw = true;
      }
      else
      {
        this.m_contentHandler.processingInstruction(pi.getNodeName(),
                                                    pi.getData());
      }
    }
    break;
    case Node.CDATA_SECTION_NODE :
    {
      boolean isLexH = (m_contentHandler instanceof LexicalHandler);
      LexicalHandler lh = isLexH
                          ? ((LexicalHandler) this.m_contentHandler) : null;

      if (isLexH)
      {
        lh.startCDATA();
      }

      dispatachChars(node);

      {
        if (isLexH)
        {
          lh.endCDATA();
        }
      }
    }
    break;
    case Node.TEXT_NODE :
    {
      //String data = ((Text) node).getData();

      if (nextIsRaw)
      {
        nextIsRaw = false;

        m_contentHandler.processingInstruction(javax.xml.transform.Result.PI_DISABLE_OUTPUT_ESCAPING, "");
        dispatachChars(node);
        m_contentHandler.processingInstruction(javax.xml.transform.Result.PI_ENABLE_OUTPUT_ESCAPING, "");
      }
      else
      {
        dispatachChars(node);
      }
    }
    break;
    case Node.ENTITY_REFERENCE_NODE :
    {
      EntityReference eref = (EntityReference) node;

      if (m_contentHandler instanceof LexicalHandler)
      {
        ((LexicalHandler) this.m_contentHandler).startEntity(
          eref.getNodeName());
      }
      else
      {

        // warning("Can not output entity to a pure SAX ContentHandler");
      }
    }
    break;
    default :
    }
  }

  /**
   * End processing of given node
   *
   *
   * @param node Node we just finished processing
   *
   * @throws org.xml.sax.SAXException
   */
  protected void endNode(Node node) throws org.xml.sax.SAXException
  {

    switch (node.getNodeType())
    {
    case Node.DOCUMENT_NODE :
      break;

    case Node.ELEMENT_NODE :
      String ns = m_dh.getNamespaceOfNode(node);
      if(null == ns)
        ns = "";
      this.m_contentHandler.endElement(ns,
                                         m_dh.getLocalNameOfNode(node),
                                         node.getNodeName());

      if (m_Serializer == null) {
      // Don't bother with endPrefixMapping calls if the ContentHandler is a
      // SerializationHandler because SerializationHandler's ignore the
      // endPrefixMapping() calls anyways. . . .  This is an optimization.
      Element elem_node = (Element) node;
      NamedNodeMap atts = elem_node.getAttributes();
      int nAttrs = atts.getLength();

      // do the endPrefixMapping calls in reverse order
      // of the startPrefixMapping calls
      for (int i = (nAttrs-1); 0 <= i; i--)
      {
        final Node attr = atts.item(i);
        final String attrName = attr.getNodeName();
        final int colon = attrName.indexOf(':');
        final String prefix;

        if (attrName.equals("xmlns") || attrName.startsWith("xmlns:"))
        {
          // Use "" instead of null, as Xerces likes "" for the
          // name of the default namespace.  Fix attributed
          // to "Steven Murray" <smurray@ebt.com>.
          if (colon < 0)
            prefix = "";
          else
            prefix = attrName.substring(colon + 1);

          this.m_contentHandler.endPrefixMapping(prefix);
        }
        else if (colon > 0) {
            prefix = attrName.substring(0, colon);
            this.m_contentHandler.endPrefixMapping(prefix);
        }
      }
      {
          String uri = elem_node.getNamespaceURI();
          if (uri != null) {
              String prefix = elem_node.getPrefix();
              if (prefix==null)
                prefix="";
              this.m_contentHandler.endPrefixMapping(prefix);
          }
      }
      }
      break;
    case Node.CDATA_SECTION_NODE :
      break;
    case Node.ENTITY_REFERENCE_NODE :
    {
      EntityReference eref = (EntityReference) node;

      if (m_contentHandler instanceof LexicalHandler)
      {
        LexicalHandler lh = ((LexicalHandler) this.m_contentHandler);

        lh.endEntity(eref.getNodeName());
      }
    }
    break;
    default :
    }
  }
}  //TreeWalker