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Java > Open Source Codes > org > apache > xalan > extensions > ExpressionContext


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 /*
17  * $Id: ExpressionContext.java,v 1.8 2004/02/11 05:26:23 minchau Exp $
18  */
19 package org.apache.xalan.extensions;
20
21 import javax.xml.transform.ErrorListener JavaDoc;
22
23 import org.apache.xpath.objects.XObject;
24 import org.w3c.dom.Node JavaDoc;
25 import org.w3c.dom.traversal.NodeIterator;
26
27 /**
28  * An object that implements this interface can supply
29  * information about the current XPath expression context.
30  */
31 public interface ExpressionContext
32 {
33
34   /**
35    * Get the current context node.
36    * @return The current context node.
37    */
38   public Node JavaDoc getContextNode();
39
40   /**
41    * Get the current context node list.
42    * @return An iterator for the current context list, as
43    * defined in XSLT.
44    */
45   public NodeIterator getContextNodes();
46   
47   /**
48    * Get the error listener.
49    * @return The registered error listener.
50    */
51   public ErrorListener JavaDoc getErrorListener();
52
53   /**
54    * Get the value of a node as a number.
55    * @param n Node to be converted to a number. May be null.
56    * @return value of n as a number.
57    */
58   public double toNumber(Node JavaDoc n);
59
60   /**
61    * Get the value of a node as a string.
62    * @param n Node to be converted to a string. May be null.
63    * @return value of n as a string, or an empty string if n is null.
64    */
65   public String JavaDoc toString(Node JavaDoc n);
66
67   /**
68    * Get a variable based on it's qualified name.
69    *
70    * @param qname The qualified name of the variable.
71    *
72    * @return The evaluated value of the variable.
73    *
74    * @throws javax.xml.transform.TransformerException
75    */
76   public XObject getVariableOrParam(org.apache.xml.utils.QName qname)
77             throws javax.xml.transform.TransformerException JavaDoc;
78   
79   /**
80    * Get the XPathContext that owns this ExpressionContext.
81    *
82    * Note: exslt:function requires the XPathContext to access
83    * the variable stack and TransformerImpl.
84    *
85    * @return The current XPathContext.
86    * @throws javax.xml.transform.TransformerException
87    */
88   public org.apache.xpath.XPathContext getXPathContext()
89             throws javax.xml.transform.TransformerException JavaDoc;
90
91 }
92
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