locpathiterator.java

java1.6众多例子参考

/*
 * 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: LocPathIterator.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.xalan.internal.res.XSLMessages;
import com.sun.org.apache.xml.internal.dtm.DTM;
import com.sun.org.apache.xml.internal.dtm.DTMFilter;
import com.sun.org.apache.xml.internal.dtm.DTMIterator;
import com.sun.org.apache.xml.internal.dtm.DTMManager;
import com.sun.org.apache.xml.internal.utils.PrefixResolver;
import com.sun.org.apache.xpath.internal.ExpressionOwner;
import com.sun.org.apache.xpath.internal.XPathContext;
import com.sun.org.apache.xpath.internal.XPathVisitor;
import com.sun.org.apache.xpath.internal.compiler.Compiler;
import com.sun.org.apache.xpath.internal.objects.XNodeSet;
import com.sun.org.apache.xpath.internal.objects.XObject;
import com.sun.org.apache.xpath.internal.res.XPATHErrorResources;

/**
 * This class extends NodeSetDTM, which implements NodeIterator,
 * and fetches nodes one at a time in document order based on a XPath
 * <a href="http://www.w3.org/TR/xpath#NT-LocationPath>LocationPath</a>.
 *
 * <p>If setShouldCacheNodes(true) is called,
 * as each node is iterated via nextNode(), the node is also stored
 * in the NodeVector, so that previousNode() can easily be done, except in
 * the case where the LocPathIterator is "owned" by a UnionPathIterator,
 * in which case the UnionPathIterator will cache the nodes.</p>
 * @xsl.usage advanced
 */
public abstract class LocPathIterator extends PredicatedNodeTest
        implements Cloneable, DTMIterator, java.io.Serializable, PathComponent
{
    static final long serialVersionUID = -4602476357268405754L;
	
  /**
   * Create a LocPathIterator object.
   *
   */
  protected LocPathIterator()
  {
  }


  /**
   * Create a LocPathIterator object.
   *
   * @param nscontext The namespace context for this iterator,
   * should be OK if null.
   */
  protected LocPathIterator(PrefixResolver nscontext)
  {

    setLocPathIterator(this);
    m_prefixResolver = nscontext;
  }

  /**
   * 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.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected LocPathIterator(Compiler compiler, int opPos, int analysis)
          throws javax.xml.transform.TransformerException
  {
    this(compiler, opPos, analysis, true);
  }

  /**
   * 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 shouldLoadWalkers True if walkers should be
   * loaded, or false if this is a derived iterator and
   * it doesn't wish to load child walkers.
   *
   * @throws javax.xml.transform.TransformerException
   */
  protected LocPathIterator(
          Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers)
            throws javax.xml.transform.TransformerException
  {
    setLocPathIterator(this);
  }
  
  /** 
   * Get the analysis bits for this walker, as defined in the WalkerFactory.
   * @return One of WalkerFactory#BIT_DESCENDANT, etc.
   */
  public int getAnalysisBits()
  {
  	int axis = getAxis();
  	int bit = WalkerFactory.getAnalysisBitFromAxes(axis);
  	return bit;
  }
  
  /**
   * Read the object from a serialization stream.
   *
   * @param stream Input stream to read from
   *
   * @throws java.io.IOException
   * @throws javax.xml.transform.TransformerException
   */
  private void readObject(java.io.ObjectInputStream stream)
          throws java.io.IOException, javax.xml.transform.TransformerException
  {
    try
    {
      stream.defaultReadObject();
      m_clones =  new IteratorPool(this);
    }
    catch (ClassNotFoundException cnfe)
    {
      throw new javax.xml.transform.TransformerException(cnfe);
    }
  }
  
  /**
   * Set the environment in which this iterator operates, which should provide:
   * a node (the context node... same value as "root" defined below) 
   * a pair of non-zero positive integers (the context position and the context size) 
   * a set of variable bindings 
   * a function library 
   * the set of namespace declarations in scope for the expression.
   * 
   * <p>At this time the exact implementation of this environment is application 
   * dependent.  Probably a proper interface will be created fairly soon.</p>
   * 
   * @param environment The environment object.
   */
  public void setEnvironment(Object environment)
  {
    // no-op for now.
  }
  
  /**
   * Get an instance of a DTM that "owns" a node handle.  Since a node 
   * iterator may be passed without a DTMManager, this allows the 
   * caller to easily get the DTM using just the iterator.
   *
   * @param nodeHandle the nodeHandle.
   *
   * @return a non-null DTM reference.
   */
  public DTM getDTM(int nodeHandle)
  {
    // %OPT%
    return m_execContext.getDTM(nodeHandle);
  }
  
  /**
   * Get an instance of the DTMManager.  Since a node 
   * iterator may be passed without a DTMManager, this allows the 
   * caller to easily get the DTMManager using just the iterator.
   *
   * @return a non-null DTMManager reference.
   */
  public DTMManager getDTMManager()
  {
    return m_execContext.getDTMManager();
  }
  
  /**
   * Execute this iterator, meaning create a clone that can
   * store state, and initialize it for fast execution from
   * the current runtime state.  When this is called, no actual
   * query from the current context node is performed.
   *
   * @param xctxt The XPath execution context.
   *
   * @return An XNodeSet reference that holds this iterator.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public XObject execute(XPathContext xctxt)
          throws javax.xml.transform.TransformerException
  {

    XNodeSet iter = new XNodeSet((LocPathIterator)m_clones.getInstance());

    iter.setRoot(xctxt.getCurrentNode(), xctxt);

    return iter;
  }
    
  /**
   * Execute an expression in the XPath runtime context, and return the
   * result of the expression.
   *
   *
   * @param xctxt The XPath runtime context.
   * @param handler The target content handler.
   *
   * @return The result of the expression in the form of a <code>XObject</code>.
   *
   * @throws javax.xml.transform.TransformerException if a runtime exception
   *         occurs.
   * @throws org.xml.sax.SAXException
   */
  public void executeCharsToContentHandler(
          XPathContext xctxt, org.xml.sax.ContentHandler handler)
            throws javax.xml.transform.TransformerException,
                   org.xml.sax.SAXException
  {
    LocPathIterator clone = (LocPathIterator)m_clones.getInstance();

    int current = xctxt.getCurrentNode();
    clone.setRoot(current, xctxt);
    
    int node = clone.nextNode();
    DTM dtm = clone.getDTM(node);
    clone.detach();
	
    if(node != DTM.NULL)
    {
      dtm.dispatchCharactersEvents(node, handler, false);
    }
  }
  
  /**
   * Given an select expression and a context, evaluate the XPath
   * and return the resulting iterator.
   * 
   * @param xctxt The execution context.
   * @param contextNode The node that "." expresses.
   * @throws TransformerException thrown if the active ProblemListener decides
   * the error condition is severe enough to halt processing.
   *
   * @throws javax.xml.transform.TransformerException
   * @xsl.usage experimental
   */
  public DTMIterator asIterator(
          XPathContext xctxt, int contextNode)
            throws javax.xml.transform.TransformerException
  {
    XNodeSet iter = new XNodeSet((LocPathIterator)m_clones.getInstance());

    iter.setRoot(contextNode, xctxt);

    return iter;
  }

  
  /**
   * Tell if the expression is a nodeset expression.
   * 
   * @return true if the expression can be represented as a nodeset.
   */
  public boolean isNodesetExpr()
  {
    return true;
  }
  
  /**
   * Return the first node out of the nodeset, if this expression is 
   * a nodeset expression.  This is the default implementation for 
   * nodesets.  Derived classes should try and override this and return a 
   * value without having to do a clone operation.
   * @param xctxt The XPath runtime context.
   * @return the first node out of the nodeset, or DTM.NULL.
   */
  public int asNode(XPathContext xctxt)
    throws javax.xml.transform.TransformerException
  {
    DTMIterator iter = (DTMIterator)m_clones.getInstance();
    
    int current = xctxt.getCurrentNode();
    
    iter.setRoot(current, xctxt);

    int next = iter.nextNode();
    // m_clones.freeInstance(iter);
    iter.detach();
    return next;
  }
  
  /**
   * Evaluate this operation directly to a boolean.
   *
   * @param xctxt The runtime execution context.
   *
   * @return The result of the operation as a boolean.
   *
   * @throws javax.xml.transform.TransformerException
   */
  public boolean bool(XPathContext xctxt)
          throws javax.xml.transform.TransformerException
  {
    return (asNode(xctxt) != DTM.NULL);
  }


  /**
   * Set if this is an iterator at the upper level of
   * the XPath.
   *
   * @param b true if this location path is at the top level of the
   *          expression.
   * @xsl.usage advanced
   */
  public void setIsTopLevel(boolean b)
  {
    m_isTopLevel = b;
  }

  /**
   * Get if this is an iterator at the upper level of
   * the XPath.
   *
   * @return true if this location path is at the top level of the
   *          expression.
   * @xsl.usage advanced
   */
  public boolean getIsTopLevel()
  {
    return m_isTopLevel;
  }
  
  /**
   * 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)
  {

    m_context = context;
    
    XPathContext xctxt = (XPathContext)environment;
    m_execContext = xctxt;
    m_cdtm = xctxt.getDTM(context);
    
    m_currentContextNode = context; // only if top level?
    
    // Yech, shouldn't have to do this.  -sb
    if(null == m_prefixResolver)
    	m_prefixResolver = xctxt.getNamespaceContext();
        
    m_lastFetched = DTM.NULL;
    m_foundLast = false;
    m_pos = 0;
    m_length = -1;

    if (m_isTopLevel)
      this.m_stackFrame = xctxt.getVarStack().getStackFrame();
      
    // reset();
  }

  /**
   * Set the next position index of this iterator.
   *
   * @param next A value greater than or equal to zero that indicates the next
   * node position to fetch.
   */
  protected void setNextPosition(int next)
  {
    assertion(false, "setNextPosition not supported in this iterator!");
  }

  /**
   * Get the current position, which is one less than
   * the next nextNode() call will retrieve.  i.e. if
   * you call getCurrentPos() and the return is 0, the next
   * fetch will take place at index 1.
   *
   * @return A value greater than or equal to zero that indicates the next
   * node position to fetch.
   */
  public final int getCurrentPos()
  {
    return m_pos;
  }


  /**
   * If setShouldCacheNodes(true) is called, then nodes will
   * be cached.  They are not cached by default.
   *
   * @param b True if this iterator should cache nodes.
   */
  public void setShouldCacheNodes(boolean b)
  {

    assertion(false, "setShouldCacheNodes not supported by this iterater!");
  }
  
  /**
   * Tells if this iterator can have nodes added to it or set via 
   * the <code>setItem(int node, int index)</code> method.
   * 
   * @return True if the nodelist can be mutated.
   */
  public boolean isMutable()
  {
    return false;
  }

  /**
   * Set the current position in the node set.
   *
   * @param i Must be a valid index greater
   * than or equal to zero and less than m_cachedNodes.size().
   */
  public void setCurrentPos(int i)
  {
  	assertion(false, "setCurrentPos not supported by this iterator!");
  }
  
  /**
   * Increment the current position in the node set.
   */
  public void incrementCurrentPos()
  {
  	m_pos++;
  }


  /**
   * Get the length of the cached nodes.
   *
   * <p>Note: for the moment at least, this only returns
   * the size of the nodes that have been fetched to date,
   * it doesn't attempt to run to the end to make sure we
   * have found everything.  This should be reviewed.</p>
   *
   * @return The size of the current cache list.
   */
  public int size()
  {
	assertion(false, "size() not supported by this iterator!");
	return 0;
  }

  /**
   *  Returns the <code>index</code> th item in the collection. If
   * <code>index</code> is greater than or equal to the number of nodes in
   * the list, this returns <code>null</code> .
   * @param index  Index into the collection.
   * @return  The node at the <code>index</code> th position in the
   *   <code>NodeList</code> , or <code>null</code> if that is not a valid
   *   index.
   */
  public int item(int index)
  {
	assertion(false, "item(int index) not supported by this iterator!");
	return 0;
  }
  
  /**
   * Sets the node at the specified index of this vector to be the
   * specified node. The previous component at that position is discarded.
   *
   * <p>The index must be a value greater than or equal to 0 and less
   * than the current size of the vector.  
   * The iterator must be in cached mode.</p>
   * 
   * <p>Meant to be used for sorted iterators.</p>
   *
   * @param node Node to set
   * @param index Index of where to set the node
   */
  public void setItem(int node, int index)
  {
	assertion(false, "setItem not supported by this iterator!");
  }

  /**
   *  The number of nodes in the list. The range of valid child node indices
   * is 0 to <code>length-1</code> inclusive.
   *
   * @return The number of nodes in the list, always greater or equal to zero.
   */
  public int getLength()
  {      
    // Tell if this is being called from within a predicate.
  	boolean isPredicateTest = (this == m_execContext.getSubContextList());

    // And get how many total predicates are part of this step.
  	int predCount = getPredicateCount();
  	
    // If we have already calculated the length, and the current predicate 
    // is the first predicate, then return the length.  We don't cache 
    // the anything but the length of the list to the first predicate.
    if (-1 != m_length && isPredicateTest && m_predicateIndex < 1)