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: PrefixResolverDefault.java 468655 2006-10-28 07:12:06Z minchau $
20 */
21package org.apache.xml.utils;
22
23import org.w3c.dom.NamedNodeMap;
24import org.w3c.dom.Node;
25
26/**
27 * This class implements a generic PrefixResolver that
28 * can be used to perform prefix-to-namespace lookup
29 * for the XPath object.
30 * @xsl.usage general
31 */
32public class PrefixResolverDefault implements PrefixResolver
33{
34
35  /**
36   * The context to resolve the prefix from, if the context
37   * is not given.
38   */
39  Node m_context;
40
41  /**
42   * Construct a PrefixResolverDefault object.
43   * @param xpathExpressionContext The context from
44   * which XPath expression prefixes will be resolved.
45   * Warning: This will not work correctly if xpathExpressionContext
46   * is an attribute node.
47   */
48  public PrefixResolverDefault(Node xpathExpressionContext)
49  {
50    m_context = xpathExpressionContext;
51  }
52
53  /**
54   * Given a namespace, get the corrisponding prefix.  This assumes that
55   * the PrevixResolver hold's it's own namespace context, or is a namespace
56   * context itself.
57   * @param prefix Prefix to resolve.
58   * @return Namespace that prefix resolves to, or null if prefix
59   * is not bound.
60   */
61  public String getNamespaceForPrefix(String prefix)
62  {
63    return getNamespaceForPrefix(prefix, m_context);
64  }
65
66  /**
67   * Given a namespace, get the corrisponding prefix.
68   * Warning: This will not work correctly if namespaceContext
69   * is an attribute node.
70   * @param prefix Prefix to resolve.
71   * @param namespaceContext Node from which to start searching for a
72   * xmlns attribute that binds a prefix to a namespace.
73   * @return Namespace that prefix resolves to, or null if prefix
74   * is not bound.
75   */
76  public String getNamespaceForPrefix(String prefix,
77                                      org.w3c.dom.Node namespaceContext)
78  {
79
80    Node parent = namespaceContext;
81    String namespace = null;
82
83    if (prefix.equals("xml"))
84    {
85      namespace = Constants.S_XMLNAMESPACEURI;
86    }
87    else
88    {
89      int type;
90
91      while ((null != parent) && (null == namespace)
92             && (((type = parent.getNodeType()) == Node.ELEMENT_NODE)
93                 || (type == Node.ENTITY_REFERENCE_NODE)))
94      {
95        if (type == Node.ELEMENT_NODE)
96        {
97                if (parent.getNodeName().indexOf(prefix+":") == 0)
98                        return parent.getNamespaceURI();
99          NamedNodeMap nnm = parent.getAttributes();
100
101          for (int i = 0; i < nnm.getLength(); i++)
102          {
103            Node attr = nnm.item(i);
104            String aname = attr.getNodeName();
105            boolean isPrefix = aname.startsWith("xmlns:");
106
107            if (isPrefix || aname.equals("xmlns"))
108            {
109              int index = aname.indexOf(':');
110              String p = isPrefix ? aname.substring(index + 1) : "";
111
112              if (p.equals(prefix))
113              {
114                namespace = attr.getNodeValue();
115
116                break;
117              }
118            }
119          }
120        }
121
122        parent = parent.getParentNode();
123      }
124    }
125
126    return namespace;
127  }
128
129  /**
130   * Return the base identifier.
131   *
132   * @return null
133   */
134  public String getBaseIdentifier()
135  {
136    return null;
137  }
138	/**
139	 * @see PrefixResolver#handlesNullPrefixes()
140	 */
141	public boolean handlesNullPrefixes() {
142		return false;
143	}
144
145}
146