| 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; |
| } |
| |
| } |
| |