code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the  "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  // $Id$
  
  package org.apache.xpath.jaxp;
  
  import org.w3c.dom.Node;
  import org.w3c.dom.NamedNodeMap;
  import org.apache.xml.utils.PrefixResolver;
  
  import javax.xml.namespace.NamespaceContext;
  
  /**
   * <meta name="usage" content="general"/>
   * This class implements a Default PrefixResolver which
   * can be used to perform prefix-to-namespace lookup
   * for the XPath object.
   * This class delegates the resolution to the passed NamespaceContext
   */
  public class JAXPPrefixResolver implements PrefixResolver
  {
  
      private NamespaceContext namespaceContext;
      
  
      public JAXPPrefixResolver ( NamespaceContext nsContext ) {
          this.namespaceContext = nsContext;
      } 
  
  
      public String getNamespaceForPrefix( String prefix ) {
          return namespaceContext.getNamespaceURI( prefix );
      }
  
      /**
       * Return the base identifier.
       *
       * @return null
       */
      public String getBaseIdentifier() {
          return null;
      }
  
      /**
       * @see PrefixResolver#handlesNullPrefixes() 
       */
      public boolean handlesNullPrefixes() {
          return false;
      }
  
  
      /**
       * The URI for the XML namespace.
       * (Duplicate of that found in org.apache.xpath.XPathContext). 
       */
       
      public static final String S_XMLNAMESPACEURI =
          "http://www.w3.org/XML/1998/namespace";
  
  
      /**
       * Given a prefix and a Context Node, get the corresponding namespace.
       * Warning: This will not work correctly if namespaceContext
       * is an attribute node.
       * @param prefix Prefix to resolve.
       * @param namespaceContext Node from which to start searching for a
       * xmlns attribute that binds a prefix to a namespace.
       * @return Namespace that prefix resolves to, or null if prefix
       * is not bound.
       */
      public String getNamespaceForPrefix(String prefix,
                                        org.w3c.dom.Node namespaceContext) {
          Node parent = namespaceContext;
          String namespace = null;
  
          if (prefix.equals("xml")) {
              namespace = S_XMLNAMESPACEURI;
          } else {
              int type;
  
              while ((null != parent) && (null == namespace)
                  && (((type = parent.getNodeType()) == Node.ELEMENT_NODE)
                      || (type == Node.ENTITY_REFERENCE_NODE))) {
  
                  if (type == Node.ELEMENT_NODE) {
                      NamedNodeMap nnm = parent.getAttributes();
  
                      for (int i = 0; i < nnm.getLength(); i++) {
                          Node attr = nnm.item(i);
                          String aname = attr.getNodeName();
                          boolean isPrefix = aname.startsWith("xmlns:");
  
                          if (isPrefix || aname.equals("xmlns")) {
                              int index = aname.indexOf(':');
                              String p =isPrefix ?aname.substring(index + 1) :"";
  
                              if (p.equals(prefix)) {
                                  namespace = attr.getNodeValue();
                                  break;
                              }
                          }
                      }
                  }
  
                  parent = parent.getParentNode();
              }
          }
          return namespace;
      }
  
  }
  
  