Java example source code file (MatchPatternIterator.java)

This example Java source code file (MatchPatternIterator.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

debug, dtmaxistraverser, locpathiterator, matchpatterniterator, object, steppattern, xobject, xpathcontext

The MatchPatternIterator.java Java example source code

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * Copyright 1999-2004 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: MatchPatternIterator.java,v 1.2.4.2 2005/09/14 19:45:22 jeffsuttor Exp $
 */
package com.sun.org.apache.xpath.internal.axes;

import com.sun.org.apache.xml.internal.dtm.Axis;
import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMAxisTraverser;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xpath.internal.XPathContext;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.compiler.OpMap;
import com.sun.org.apache.xpath.internal.objects.XObject;
import com.sun.org.apache.xpath.internal.patterns.NodeTest;
import com.sun.org.apache.xpath.internal.patterns.StepPattern;

/**
 * This class treats a
 * <a href="http://www.w3.org/TR/xpath#location-paths">LocationPath as a
 * filtered iteration over the tree, evaluating each node in a super axis
 * traversal against the LocationPath interpreted as a match pattern.  This
 * class is useful to find nodes in document order that are complex paths
 * whose steps probably criss-cross each other.
 */
public class MatchPatternIterator extends LocPathIterator
{
    static final long serialVersionUID = -5201153767396296474L;

  /** This is the select pattern, translated into a match pattern. */
  protected StepPattern m_pattern;

  /** The traversal axis from where the nodes will be filtered. */
  protected int m_superAxis = -1;

  /** The DTM inner traversal class, that corresponds to the super axis. */
  protected DTMAxisTraverser m_traverser;

  /** DEBUG flag for diagnostic dumps. */
  private static final boolean DEBUG = false;

//  protected int m_nsElemBase = DTM.NULL;

  /**
   * Create a LocPathIterator object, including creation
   * of step walkers from the opcode list, and call back
   * into the Compiler to create predicate expressions.
   *
   * @param compiler The Compiler which is creating
   * this expression.
   * @param opPos The position of this iterator in the
   * opcode list from the compiler.
   * @param analysis Analysis bits that give general information about the
   * LocationPath.
   *
   * @throws javax.xml.transform.TransformerException
   */
  MatchPatternIterator(Compiler compiler, int opPos, int analysis)
          throws javax.xml.transform.TransformerException
  {

    super(compiler, opPos, analysis, false);

    int firstStepPos = OpMap.getFirstChildPos(opPos);

    m_pattern = WalkerFactory.loadSteps(this, compiler, firstStepPos, 0);

    boolean fromRoot = false;
    boolean walkBack = false;
    boolean walkDescendants = false;
    boolean walkAttributes = false;

    if (0 != (analysis & (WalkerFactory.BIT_ROOT |
                          WalkerFactory.BIT_ANY_DESCENDANT_FROM_ROOT)))
      fromRoot = true;

    if (0 != (analysis
              & (WalkerFactory.BIT_ANCESTOR
                 | WalkerFactory.BIT_ANCESTOR_OR_SELF
                 | WalkerFactory.BIT_PRECEDING
                 | WalkerFactory.BIT_PRECEDING_SIBLING
                 | WalkerFactory.BIT_FOLLOWING
                 | WalkerFactory.BIT_FOLLOWING_SIBLING
                 | WalkerFactory.BIT_PARENT | WalkerFactory.BIT_FILTER)))
      walkBack = true;

    if (0 != (analysis
              & (WalkerFactory.BIT_DESCENDANT_OR_SELF
                 | WalkerFactory.BIT_DESCENDANT
                 | WalkerFactory.BIT_CHILD)))
      walkDescendants = true;

    if (0 != (analysis
              & (WalkerFactory.BIT_ATTRIBUTE | WalkerFactory.BIT_NAMESPACE)))
      walkAttributes = true;

    if(false || DEBUG)
    {
      System.out.print("analysis: "+Integer.toBinaryString(analysis));
      System.out.println(", "+WalkerFactory.getAnalysisString(analysis));
    }

    if(fromRoot || walkBack)
    {
      if(walkAttributes)
      {
        m_superAxis = Axis.ALL;
      }
      else
      {
        m_superAxis = Axis.DESCENDANTSFROMROOT;
      }
    }
    else if(walkDescendants)
    {
      if(walkAttributes)
      {
        m_superAxis = Axis.ALLFROMNODE;
      }
      else
      {
        m_superAxis = Axis.DESCENDANTORSELF;
      }
    }
    else
    {
      m_superAxis = Axis.ALL;
    }
    if(false || DEBUG)
    {
      System.out.println("axis: "+Axis.getNames(m_superAxis));
    }

  }


  /**
   * Initialize the context values for this expression
   * after it is cloned.
   *
   * @param context The XPath runtime context for this
   * transformation.
   */
  public void setRoot(int context, Object environment)
  {
    super.setRoot(context, environment);
    m_traverser = m_cdtm.getAxisTraverser(m_superAxis);
  }

  /**
   *  Detaches the iterator from the set which it iterated over, releasing
   * any computational resources and placing the iterator in the INVALID
   * state. After<code>detach has been invoked, calls to
   * <code>nextNode orpreviousNode will raise the
   * exception INVALID_STATE_ERR.
   */
  public void detach()
  {
    if(m_allowDetach)
    {
      m_traverser = null;

      // Always call the superclass detach last!
      super.detach();
    }
  }

  /**
   * Get the next node via getNextXXX.  Bottlenecked for derived class override.
   * @return The next node on the axis, or DTM.NULL.
   */
  protected int getNextNode()
  {
    m_lastFetched = (DTM.NULL == m_lastFetched)
                     ? m_traverser.first(m_context)
                     : m_traverser.next(m_context, m_lastFetched);
    return m_lastFetched;
  }

  /**
   *  Returns the next node in the set and advances the position of the
   * iterator in the set. After a NodeIterator is created, the first call
   * to nextNode() returns the first node in the set.
   * @return  The next <code>Node in the set being iterated over, or
   *   <code>null if there are no more members in that set.
   */
  public int nextNode()
  {
        if(m_foundLast)
                return DTM.NULL;

    int next;

    com.sun.org.apache.xpath.internal.VariableStack vars;
    int savedStart;
    if (-1 != m_stackFrame)
    {
      vars = m_execContext.getVarStack();

      // These three statements need to be combined into one operation.
      savedStart = vars.getStackFrame();

      vars.setStackFrame(m_stackFrame);
    }
    else
    {
      // Yuck.  Just to shut up the compiler!
      vars = null;
      savedStart = 0;
    }

    try
    {
      if(DEBUG)
        System.out.println("m_pattern"+m_pattern.toString());

      do
      {
        next = getNextNode();

        if (DTM.NULL != next)
        {
          if(DTMIterator.FILTER_ACCEPT == acceptNode(next, m_execContext))
            break;
          else
            continue;
        }
        else
          break;
      }
      while (next != DTM.NULL);

      if (DTM.NULL != next)
      {
        if(DEBUG)
        {
          System.out.println("next: "+next);
          System.out.println("name: "+m_cdtm.getNodeName(next));
        }
        incrementCurrentPos();

        return next;
      }
      else
      {
        m_foundLast = true;

        return DTM.NULL;
      }
    }
    finally
    {
      if (-1 != m_stackFrame)
      {
        // These two statements need to be combined into one operation.
        vars.setStackFrame(savedStart);
      }
    }

  }

  /**
   *  Test whether a specified node is visible in the logical view of a
   * TreeWalker or NodeIterator. This function will be called by the
   * implementation of TreeWalker and NodeIterator; it is not intended to
   * be called directly from user code.
   * @param n  The node to check to see if it passes the filter or not.
   * @return  a constant to determine whether the node is accepted,
   *   rejected, or skipped, as defined  above .
   */
  public short acceptNode(int n, XPathContext xctxt)
  {

    try
    {
      xctxt.pushCurrentNode(n);
      xctxt.pushIteratorRoot(m_context);
      if(DEBUG)
      {
        System.out.println("traverser: "+m_traverser);
        System.out.print("node: "+n);
        System.out.println(", "+m_cdtm.getNodeName(n));
        // if(m_cdtm.getNodeName(n).equals("near-east"))
        System.out.println("pattern: "+m_pattern.toString());
        m_pattern.debugWhatToShow(m_pattern.getWhatToShow());
      }

      XObject score = m_pattern.execute(xctxt);

      if(DEBUG)
      {
        // System.out.println("analysis: "+Integer.toBinaryString(m_analysis));
        System.out.println("score: "+score);
        System.out.println("skip: "+(score == NodeTest.SCORE_NONE));
      }

      // System.out.println("\n::acceptNode - score: "+score.num()+"::");
      return (score == NodeTest.SCORE_NONE) ? DTMIterator.FILTER_SKIP
                    : DTMIterator.FILTER_ACCEPT;
    }
    catch (javax.xml.transform.TransformerException se)
    {

      // TODO: Fix this.
      throw new RuntimeException(se.getMessage());
    }
    finally
    {
      xctxt.popCurrentNode();
      xctxt.popIteratorRoot();
    }

  }

}