# Interface XPathNSResolver

public interface XPathNSResolver
The `XPathNSResolver` interface permit `prefix` strings in the expression to be properly bound to `namespaceURI` strings. `XPathEvaluator` can construct an implementation of `XPathNSResolver` from a node, or the interface may be implemented by any application.

See also the Document Object Model (DOM) Level 3 XPath Specification.

Since:
  1.4, DOM Level 3

- ## Method Summary

  Modifier and Type
  Method
  Description
  `String`
  `lookupNamespaceURI(String prefix)`
  Look up the namespace URI associated to the given namespace prefix.

- ## Method Details

  - ### lookupNamespaceURI

    String lookupNamespaceURI(String prefix)
    Look up the namespace URI associated to the given namespace prefix. The XPath evaluator must never call this with a `null` or empty argument, because the result of doing this is undefined.
    Parameters:
      `prefix` - The prefix to look for.
    Returns:
      Returns the associated namespace URI or `null` if none is found.