RE: XPathAPI help needed

[Scott Moore]

Paul,

I've tried what you suggested, but it won't compile because the
namespaceNode (3rd parameter) must be of type Node.  For instance,

    Node n = XPathAPI.selectSingleNode(currentNode, xpath, 
            new org.apache.xml.utils.PrefixResolverDefault(contextNode));

doesn't compile.

What am I missing here?

Thanks,
Scott

-----Original Message-----
From: Paul Brown [mailto:[EMAIL PROTECTED]]
Sent: Monday, December 03, 2001 11:10 AM
To: [EMAIL PROTECTED]
Subject: RE: XPathAPI help needed



> [Scott.Moore at netDecide.com]
> Subject: XPathAPI help needed
> Everything works fine unless the XML has namespaces and I try to
> reference them in my XPath expression.

You have two choices:

1) You need to create a dummy prefix resolver that knows about your
namespaces; you can do this by implementing the relevant interface
(org.apache.xml.utils.PrefixResolver).

2) You can use a PrefixResolverDefault
(org.apache.xml.utils.PrefixResolverDefault) constructed for the context
node in your expression.  (It only has one constructor.)

Choice #1 is much better than choice #2 because choice #2 means that you're
dependent on the prefixes declared in the document.  Choice #1 means that
you're dependent on the URIs.

Tell you what, I'll contribute some code...  It follows:

import java.util.HashMap;
import java.util.Map;
import org.w3c.dom.Node;
import org.apache.xml.utils.PrefixResolver;

/**
 * This class implements the org.apache.xml.utils.PrefixResolver
 * interface to support execution of XPath expressions without
 * dependence on document-delcared namespace prefixes.
 */
public class StaticPrefixResolverImpl implements PrefixResolver
{

  /**
   * Runtime storage for prefixes and URIs.
   */
  private HashMap _prefixes;

  private static final String EMPTY_STRING = "";

  /**
   * The URI for the "xml" namespace.
   */
  public static final String S_XMLNAMESPACEURI =
    "http://www.w3.org/XML/1998/namespace";;
  public static final String XML_PREFIX = "xml";

  /**
   * The URI for namespace declarations.
   */
  public static final String S_XMLNSNAMESPACEURI =
    "http://www.w3.org/2000/xmlns/";;
  public static final String XMLNS_PREFIX = "xmlns";

  /**
   * Create a new StaticPrefixResolverImpl using the supplied map of
prefixes
   * and URIs.  The constructor creates a copy of the supplied map.
   *
   * @param prefixMap a map of the prefixes and URIs to be used by the
instance.
   */
  public StaticPrefixResolverImpl(Map prefixMap)
  {
    if (prefixMap != null) {
      _prefixes = new HashMap(prefixMap);
    } else {
      _prefixes = new HashMap();
    }
    _prefixes.put(XML_PREFIX,S_XMLNAMESPACEURI);
    _prefixes.put(XMLNS_PREFIX,S_XMLNSNAMESPACEURI);
  }

  /**
   * Return the base identifier for the document.
   */
  public String getBaseIdentifier()
  {
    return (String) _prefixes.get(EMPTY_STRING);
  }

  /**
   * Retrieve the URI corresponding to the supplied prefix.
   *
   * @param prefix the prefix to match to a URI.
   */
  public String getNamespaceForPrefix(String prefix)
  {
    return (String) _prefixes.get(prefix);
  }

  /**
   * Retrieve a namespace in context.  Note that this is meaningless for our
   * implementation, as the prefixes are static for the entire document and
   * independent of any local declarations.
   *
   * @param prefix the prefix to query
   * @param n the context Node (ignored)
   */
  public String getNamespaceForPrefix(String prefix, Node n)
  {
    return getNamespaceForPrefix(prefix);
  }

}

        -- Paul