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.xml.utils;
  
  import org.w3c.dom.NamedNodeMap;
  import org.w3c.dom.Node;
  
  /**
   * This class implements a generic PrefixResolver that
   * can be used to perform prefix-to-namespace lookup
   * for the XPath object.
   * @xsl.usage general
   */
  public class PrefixResolverDefault implements PrefixResolver
  {
  
    /**
     * The context to resolve the prefix from, if the context
     * is not given.
     */
    Node m_context;
  
    /**
     * Construct a PrefixResolverDefault object.
     * @param xpathExpressionContext The context from
     * which XPath expression prefixes will be resolved.
     * Warning: This will not work correctly if xpathExpressionContext
     * is an attribute node.
     */
    public PrefixResolverDefault(Node xpathExpressionContext)
    {
      m_context = xpathExpressionContext;
    }
  
    /**
     * Given a namespace, get the corrisponding prefix.  This assumes that
     * the PrevixResolver hold's it's own namespace context, or is a namespace
     * context itself.
     * @param prefix Prefix to resolve.
     * @return Namespace that prefix resolves to, or null if prefix
     * is not bound.
     */
    public String getNamespaceForPrefix(String prefix)
    {
      return getNamespaceForPrefix(prefix, m_context);
    }
  
    /**
     * Given a namespace, get the corrisponding prefix.
     * 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 = Constants.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)
          {
                  if (parent.getNodeName().indexOf(prefix+":") == 0) 
                          return parent.getNamespaceURI();                
            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;
    }
  
    /**
     * Return the base identifier.
     *
     * @return null
     */
    public String getBaseIdentifier()
    {
      return null;
    }
  	/**
  	 * @see PrefixResolver#handlesNullPrefixes()
  	 */
  	public boolean handlesNullPrefixes() {
  		return false;
  	}
  
  }
  