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: ExpressionContext.java 468637 2006-10-28 06:51:02Z minchau $
20 */
21package org.apache.xalan.extensions;
22
23import javax.xml.transform.ErrorListener;
24
25import org.apache.xpath.objects.XObject;
26import org.w3c.dom.Node;
27import org.w3c.dom.traversal.NodeIterator;
28
29/**
30 * An object that implements this interface can supply
31 * information about the current XPath expression context.
32 */
33public interface ExpressionContext
34{
35
36  /**
37   * Get the current context node.
38   * @return The current context node.
39   */
40  public Node getContextNode();
41
42  /**
43   * Get the current context node list.
44   * @return An iterator for the current context list, as
45   * defined in XSLT.
46   */
47  public NodeIterator getContextNodes();
48
49  /**
50   * Get the error listener.
51   * @return The registered error listener.
52   */
53  public ErrorListener getErrorListener();
54
55  /**
56   * Get the value of a node as a number.
57   * @param n Node to be converted to a number.  May be null.
58   * @return value of n as a number.
59   */
60  public double toNumber(Node n);
61
62  /**
63   * Get the value of a node as a string.
64   * @param n Node to be converted to a string.  May be null.
65   * @return value of n as a string, or an empty string if n is null.
66   */
67  public String toString(Node n);
68
69  /**
70   * Get a variable based on it's qualified name.
71   *
72   * @param qname The qualified name of the variable.
73   *
74   * @return The evaluated value of the variable.
75   *
76   * @throws javax.xml.transform.TransformerException
77   */
78  public XObject getVariableOrParam(org.apache.xml.utils.QName qname)
79            throws javax.xml.transform.TransformerException;
80
81  /**
82   * Get the XPathContext that owns this ExpressionContext.
83   *
84   * Note: exslt:function requires the XPathContext to access
85   * the variable stack and TransformerImpl.
86   *
87   * @return The current XPathContext.
88   * @throws javax.xml.transform.TransformerException
89   */
90  public org.apache.xpath.XPathContext getXPathContext()
91            throws javax.xml.transform.TransformerException;
92
93}
94