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