import com.sun.org.apache.xpath.internal.axes.LocPathIterator; //导入依赖的package包/类
/**
 * Execute the function.  The function must return
 * a valid object.
 * @param xctxt The current execution context.
 * @return A valid XObject.
 *
 * @throws javax.xml.transform.TransformerException
 */
public XObject execute(XPathContext xctxt) throws javax.xml.transform.TransformerException
{

  SubContextList subContextList = xctxt.getCurrentNodeList();
  int currentNode = DTM.NULL;

  if (null != subContextList) {
      if (subContextList instanceof PredicatedNodeTest) {
          LocPathIterator iter = ((PredicatedNodeTest)subContextList)
                                                        .getLocPathIterator();
          currentNode = iter.getCurrentContextNode();
       } else if(subContextList instanceof StepPattern) {
         throw new RuntimeException(XSLMessages.createMessage(
            XSLTErrorResources.ER_PROCESSOR_ERROR,null));
       }
  } else {
      // not predicate => ContextNode == CurrentNode
      currentNode = xctxt.getContextNode();
  }
  return new XNodeSet(currentNode, xctxt.getDTMManager());
}
 

import com.sun.org.apache.xpath.internal.axes.LocPathIterator; //导入依赖的package包/类
/**
 * Evaluate an XPath context using the internal XPath engine
 * @param contextItem The XPath context
 * @param xpath The internal XPath engine
 * @return an XObject
 * @throws javax.xml.transform.TransformerException If the expression cannot be evaluated.
 */
XObject eval(Object contextItem, com.sun.org.apache.xpath.internal.XPath xpath)
        throws javax.xml.transform.TransformerException {
    com.sun.org.apache.xpath.internal.XPathContext xpathSupport;
    if (contextItem == null && xpath.getExpression() instanceof LocPathIterator) {
        // the operation must have no dependency on the context that is null
        throw new TransformerException(XSLMessages.createXPATHMessage(
                XPATHErrorResources.ER_CONTEXT_CAN_NOT_BE_NULL,
                new Object[] {}));
    }
    if (functionResolver != null) {
        JAXPExtensionsProvider jep = new JAXPExtensionsProvider(
                functionResolver, featureSecureProcessing, featureManager);
        xpathSupport = new com.sun.org.apache.xpath.internal.XPathContext(jep);
    } else {
        xpathSupport = new com.sun.org.apache.xpath.internal.XPathContext();
    }

    xpathSupport.setVarStack(new JAXPVariableStack(variableResolver));
    XObject xobj;

    Node contextNode = (Node)contextItem;
    // We always need to have a ContextNode with Xalan XPath implementation
    // To allow simple expression evaluation like 1+1 we are setting
    // dummy Document as Context Node
    if (contextNode == null) {
        xobj = xpath.execute(xpathSupport, DTM.NULL, prefixResolver);
    } else {
        xobj = xpath.execute(xpathSupport, contextNode, prefixResolver);
    }

    return xobj;
}
 

import com.sun.org.apache.xpath.internal.axes.LocPathIterator; //导入依赖的package包/类
/**
 * Visit a LocationPath.
 * @param owner The owner of the expression, to which the expression can
 *              be reset if rewriting takes place.
 * @param path The LocationPath object.
 * @return true if the sub expressions should be traversed.
 */
public boolean visitLocationPath(ExpressionOwner owner, LocPathIterator path)
{
        return true;
}