1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one 3 * or more contributor license agreements. See the NOTICE file 4 * distributed with this work for additional information 5 * regarding copyright ownership. The ASF licenses this file 6 * to you under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 /* 19 * $Id: VariableSafeAbsRef.java 468655 2006-10-28 07:12:06Z minchau $ 20 */ 21 package org.apache.xpath.operations; 22 23 import org.apache.xml.dtm.DTMManager; 24 import org.apache.xpath.Expression; 25 import org.apache.xpath.XPathContext; 26 import org.apache.xpath.objects.XNodeSet; 27 import org.apache.xpath.objects.XObject; 28 29 30 /** 31 * This is a "smart" variable reference that is used in situations where 32 * an absolute path is optimized into a variable reference, but may 33 * be used in some situations where the document context may have changed. 34 * For instance, in select="document(doc/@href)//name[//salary > 7250]", the 35 * root in the predicate will be different for each node in the set. While 36 * this is easy to detect statically in this case, in other cases static 37 * detection would be very hard or impossible. So, this class does a dynamic check 38 * to make sure the document context of the referenced variable is the same as 39 * the current document context, and, if it is not, execute the referenced variable's 40 * expression with the current context instead. 41 */ 42 public class VariableSafeAbsRef extends Variable 43 { 44 static final long serialVersionUID = -9174661990819967452L; 45 46 /** 47 * Dereference the variable, and return the reference value. Note that lazy 48 * evaluation will occur. If a variable within scope is not found, a warning 49 * will be sent to the error listener, and an empty nodeset will be returned. 50 * 51 * 52 * @param xctxt The runtime execution context. 53 * 54 * @return The evaluated variable, or an empty nodeset if not found. 55 * 56 * @throws javax.xml.transform.TransformerException 57 */ 58 public XObject execute(XPathContext xctxt, boolean destructiveOK) 59 throws javax.xml.transform.TransformerException 60 { 61 XNodeSet xns = (XNodeSet)super.execute(xctxt, destructiveOK); 62 DTMManager dtmMgr = xctxt.getDTMManager(); 63 int context = xctxt.getContextNode(); 64 if(dtmMgr.getDTM(xns.getRoot()).getDocument() != 65 dtmMgr.getDTM(context).getDocument()) 66 { 67 Expression expr = (Expression)xns.getContainedIter(); 68 xns = (XNodeSet)expr.asIterator(xctxt, context); 69 } 70 return xns; 71 } 72 73 } 74 75
