- package org.apache.xpath.operations;
-
- import javax.xml.transform.TransformerException;
- import org.apache.xml.dtm.DTM;
- import org.apache.xml.dtm.DTMIterator;
- import org.apache.xml.dtm.DTMManager;
- import org.apache.xpath.Expression;
- import org.apache.xpath.XPathContext;
- import org.apache.xpath.objects.XNodeSet;
- import org.apache.xpath.objects.XObject;
-
-
- /**
- * This is a "smart" variable reference that is used in situations where
- * an absolute path is optimized into a variable reference, but may
- * be used in some situations where the document context may have changed.
- * For instance, in select="document(doc/@href)//name[//salary > 7250]", the
- * root in the predicate will be different for each node in the set. While
- * this is easy to detect statically in this case, in other cases static
- * detection would be very hard or impossible. So, this class does a dynamic check
- * to make sure the document context of the referenced variable is the same as
- * the current document context, and, if it is not, execute the referenced variable's
- * expression with the current context instead.
- */
- public class VariableSafeAbsRef extends Variable
- {
-
- /**
- * Dereference the variable, and return the reference value. Note that lazy
- * evaluation will occur. If a variable within scope is not found, a warning
- * will be sent to the error listener, and an empty nodeset will be returned.
- *
- *
- * @param xctxt The runtime execution context.
- *
- * @return The evaluated variable, or an empty nodeset if not found.
- *
- * @throws javax.xml.transform.TransformerException
- */
- public XObject execute(XPathContext xctxt, boolean destructiveOK)
- throws javax.xml.transform.TransformerException
- {
- XNodeSet xns = (XNodeSet)super.execute(xctxt, destructiveOK);
- DTMManager dtmMgr = xctxt.getDTMManager();
- int context = xctxt.getContextNode();
- if(dtmMgr.getDTM(xns.getRoot()).getDocument() !=
- dtmMgr.getDTM(context).getDocument())
- {
- Expression expr = (Expression)xns.getContainedIter();
- xns = (XNodeSet)expr.asIterator(xctxt, context);
- }
- return xns;
- }
-
- }
-