org.apache.xpath.operations.VariableSafeAbsRef Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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: VariableSafeAbsRef.java 468655 2006-10-28 07:12:06Z minchau $
*/
package org.apache.xpath.operations;
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
{
static final long serialVersionUID = -9174661990819967452L;
/**
* 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;
}
}