http://xml.apache.org/commons/components/external/: xml-commons provides an Apache-hosted set of DOM, SAX, and JAXP interfaces for use in other xml-based projects. Our hope is that we can standardize on both a common version and packaging scheme for these critical XML standards interfaces to make the lives of both our developers and users easier. The External Components portion of xml-commons contains interfaces that are defined by external standards organizations. For DOM, that's the W3C; for SAX it's David Megginson and sax.sourceforge.net; for JAXP it's Sun. 
/*
 * Copyright (c) 2004 World Wide Web Consortium,
 *
 * (Massachusetts Institute of Technology, European Research Consortium for
 * Informatics and Mathematics, Keio University). All Rights Reserved. This
 * work is distributed under the W3C(r) Software License [1] in the hope that
 * it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * [1] http://www.w3.org/Consortium/Legal/2002/copyright-software-20021231
 */

package org.w3c.dom.xpath;

import org.w3c.dom.Node;
import org.w3c.dom.DOMException;


 The evaluation of XPath expressions is provided by 
XPathEvaluator. In a DOM implementation which supports the 
XPath 3.0 feature, as described above, the XPathEvaluator 
interface will be implemented on the same object which implements the 
Document interface permitting it to be obtained by the usual 
binding-specific method such as casting or by using the DOM Level 3 
getInterface method. In this case the implementation obtained from the 
Document supports the XPath DOM module and is compatible with the XPath 
1.0 specification. 

Evaluation of expressions with specialized extension functions or 
variables may not work in all implementations and is, therefore, not 
portable. XPathEvaluator implementations may be available 
from other sources that could provide specific support for specialized 
extension functions or variables as would be defined by other 
specifications. 

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

/**
 *  The evaluation of XPath expressions is provided by 
 * <code>XPathEvaluator</code>. In a DOM implementation which supports the 
 * XPath 3.0 feature, as described above, the <code>XPathEvaluator</code> 
 * interface will be implemented on the same object which implements the 
 * <code>Document</code> interface permitting it to be obtained by the usual 
 * binding-specific method such as casting or by using the DOM Level 3 
 * getInterface method. In this case the implementation obtained from the 
 * Document supports the XPath DOM module and is compatible with the XPath 
 * 1.0 specification. 
 * <p>Evaluation of expressions with specialized extension functions or 
 * variables may not work in all implementations and is, therefore, not 
 * portable. <code>XPathEvaluator</code> implementations may be available 
 * from other sources that could provide specific support for specialized 
 * extension functions or variables as would be defined by other 
 * specifications. 
 * <p>See also the <a href='http://www.w3.org/TR/2004/NOTE-DOM-Level-3-XPath-20040226'>Document Object Model (DOM) Level 3 XPath Specification</a>.
 */
public interface XPathEvaluator {
    
Creates a parsed XPath expression with resolved namespaces. This is 
useful when an expression will be reused in an application since it 
makes it possible to compile the expression string into a more 
efficient internal form and preresolve all namespace prefixes which 
occur within the expression.

Params:
  • expression – The XPath expression string to be parsed.
  • resolver – The resolver permits translation of all 
  prefixes, including the xml namespace prefix, within 
  the XPath expression into appropriate namespace URIs. If this is 
  specified as null, any namespace prefix within the 
  expression will result in DOMException being thrown 
  with the code NAMESPACE_ERR.
Throws:
  • XPathException – 
  INVALID_EXPRESSION_ERR: Raised if the expression is not legal 
  according to the rules of the XPathEvaluator.
  • DOMException – 
  NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
  which cannot be resolved by the specified 
  XPathNSResolver.
Returns:The compiled form of the XPath expression.
/**
     * Creates a parsed XPath expression with resolved namespaces. This is 
     * useful when an expression will be reused in an application since it 
     * makes it possible to compile the expression string into a more 
     * efficient internal form and preresolve all namespace prefixes which 
     * occur within the expression.
     * @param expression The XPath expression string to be parsed.
     * @param resolver The <code>resolver</code> permits translation of all 
     *   prefixes, including the <code>xml</code> namespace prefix, within 
     *   the XPath expression into appropriate namespace URIs. If this is 
     *   specified as <code>null</code>, any namespace prefix within the 
     *   expression will result in <code>DOMException</code> being thrown 
     *   with the code <code>NAMESPACE_ERR</code>.
     * @return The compiled form of the XPath expression.
     * @exception XPathException
     *   INVALID_EXPRESSION_ERR: Raised if the expression is not legal 
     *   according to the rules of the <code>XPathEvaluator</code>.
     * @exception DOMException
     *   NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
     *   which cannot be resolved by the specified 
     *   <code>XPathNSResolver</code>.
     */
    public XPathExpression createExpression(String expression, 
                                            XPathNSResolver resolver)
                                            throws XPathException, DOMException;

    
Adapts any DOM node to resolve namespaces so that an XPath expression 
can be easily evaluated relative to the context of the node where it 
appeared within the document. This adapter works like the DOM Level 3 
method lookupNamespaceURI on nodes in resolving the 
namespaceURI from a given prefix using the current information 
available in the node's hierarchy at the time lookupNamespaceURI is 
called. also correctly resolving the implicit xml prefix.

Params:
  • nodeResolver – The node to be used as a context for namespace 
  resolution.
Returns:XPathNSResolver which resolves namespaces with 
  respect to the definitions in scope for a specified node.
/**
     * Adapts any DOM node to resolve namespaces so that an XPath expression 
     * can be easily evaluated relative to the context of the node where it 
     * appeared within the document. This adapter works like the DOM Level 3 
     * method <code>lookupNamespaceURI</code> on nodes in resolving the 
     * namespaceURI from a given prefix using the current information 
     * available in the node's hierarchy at the time lookupNamespaceURI is 
     * called. also correctly resolving the implicit xml prefix.
     * @param nodeResolver The node to be used as a context for namespace 
     *   resolution.
     * @return <code>XPathNSResolver</code> which resolves namespaces with 
     *   respect to the definitions in scope for a specified node.
     */
    public XPathNSResolver createNSResolver(Node nodeResolver);

    
Evaluates an XPath expression string and returns a result of the 
specified type if possible.

Params:
  • expression – The XPath expression string to be parsed and 
  evaluated.
  • contextNode – The context is context node for the 
  evaluation of this XPath expression. If the XPathEvaluator was 
  obtained by casting the Document then this must be 
  owned by the same document and must be a Document, 
  Element, Attribute, Text, 
  CDATASection, Comment, 
  ProcessingInstruction, or XPathNamespace 
  node. If the context node is a Text or a 
  CDATASection, then the context is interpreted as the 
  whole logical text node as seen by XPath, unless the node is empty 
  in which case it may not serve as the XPath context.
  • resolver – The resolver permits translation of all 
  prefixes, including the xml namespace prefix, within 
  the XPath expression into appropriate namespace URIs. If this is 
  specified as null, any namespace prefix within the 
  expression will result in DOMException being thrown 
  with the code NAMESPACE_ERR.
  • type – If a specific type is specified, then the 
  result will be returned as the corresponding type.For XPath 1.0 
  results, this must be one of the codes of the 
  XPathResult interface.
  • result – The result specifies a specific result 
  object which may be reused and returned by this method. If this is 
  specified as nullor the implementation does not reuse 
  the specified result, a new result object will be constructed and 
  returned.For XPath 1.0 results, this object will be of type 
  XPathResult.
Throws:
  • XPathException – 
  INVALID_EXPRESSION_ERR: Raised if the expression is not legal 
  according to the rules of the XPathEvaluatori
  
    TYPE_ERR: Raised if the result cannot be converted to return the 
  specified type.
  • DOMException – 
  NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
  which cannot be resolved by the specified 
  XPathNSResolver.
  
    WRONG_DOCUMENT_ERR: The Node is from a document that is not 
  supported by this XPathEvaluator.
  
    NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
  context node or the request type is not permitted by this 
  XPathEvaluator.
Returns:The result of the evaluation of the XPath expression.For XPath 
  1.0 results, this object will be of type XPathResult.
/**
     * Evaluates an XPath expression string and returns a result of the 
     * specified type if possible.
     * @param expression The XPath expression string to be parsed and 
     *   evaluated.
     * @param contextNode The <code>context</code> is context node for the 
     *   evaluation of this XPath expression. If the XPathEvaluator was 
     *   obtained by casting the <code>Document</code> then this must be 
     *   owned by the same document and must be a <code>Document</code>, 
     *   <code>Element</code>, <code>Attribute</code>, <code>Text</code>, 
     *   <code>CDATASection</code>, <code>Comment</code>, 
     *   <code>ProcessingInstruction</code>, or <code>XPathNamespace</code> 
     *   node. If the context node is a <code>Text</code> or a 
     *   <code>CDATASection</code>, then the context is interpreted as the 
     *   whole logical text node as seen by XPath, unless the node is empty 
     *   in which case it may not serve as the XPath context.
     * @param resolver The <code>resolver</code> permits translation of all 
     *   prefixes, including the <code>xml</code> namespace prefix, within 
     *   the XPath expression into appropriate namespace URIs. If this is 
     *   specified as <code>null</code>, any namespace prefix within the 
     *   expression will result in <code>DOMException</code> being thrown 
     *   with the code <code>NAMESPACE_ERR</code>.
     * @param type If a specific <code>type</code> is specified, then the 
     *   result will be returned as the corresponding type.For XPath 1.0 
     *   results, this must be one of the codes of the 
     *   <code>XPathResult</code> interface.
     * @param result The <code>result</code> specifies a specific result 
     *   object which may be reused and returned by this method. If this is 
     *   specified as <code>null</code>or the implementation does not reuse 
     *   the specified result, a new result object will be constructed and 
     *   returned.For XPath 1.0 results, this object will be of type 
     *   <code>XPathResult</code>.
     * @return The result of the evaluation of the XPath expression.For XPath 
     *   1.0 results, this object will be of type <code>XPathResult</code>.
     * @exception XPathException
     *   INVALID_EXPRESSION_ERR: Raised if the expression is not legal 
     *   according to the rules of the <code>XPathEvaluator</code>i
     *   <br>TYPE_ERR: Raised if the result cannot be converted to return the 
     *   specified type.
     * @exception DOMException
     *   NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
     *   which cannot be resolved by the specified 
     *   <code>XPathNSResolver</code>.
     *   <br>WRONG_DOCUMENT_ERR: The Node is from a document that is not 
     *   supported by this <code>XPathEvaluator</code>.
     *   <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
     *   context node or the request type is not permitted by this 
     *   <code>XPathEvaluator</code>.
     */
    public Object evaluate(String expression, 
                           Node contextNode, 
                           XPathNSResolver resolver, 
                           short type, 
                           Object result)
                           throws XPathException, DOMException;

}