http://xml.apache.org/xalan-j/: Serializer to write out XML, HTML etc. as a stream of characters from an input DOM or from input SAX events. (The Apache Software Foundation) 
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 * 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.
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 *
 *     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.
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/*
 * $Id: XPathEvaluatorImpl.java 1225443 2011-12-29 05:44:18Z mrglavas $
 */

package org.apache.xpath.domapi;

import javax.xml.transform.TransformerException;

import org.apache.xml.utils.PrefixResolver;
import org.apache.xpath.XPath;
import org.apache.xpath.res.XPATHErrorResources;
import org.apache.xpath.res.XPATHMessages;
import org.w3c.dom.DOMException;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.xpath.XPathEvaluator;
import org.w3c.dom.xpath.XPathException;
import org.w3c.dom.xpath.XPathExpression;
import org.w3c.dom.xpath.XPathNSResolver;


The class provides an implementation of XPathEvaluator according 
to the DOM L3 XPath Specification, Working Group Note 26 February 2004.

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


The evaluation of XPath expressions is provided by 
XPathEvaluator, which will provide evaluation of XPath 1.0 
expressions with no specialized extension functions or variables. It is 
expected that the XPathEvaluator interface will be 
implemented on the same object which implements the Document 
interface in an implementation which supports the XPath DOM module. 
XPathEvaluator implementations may be available from other 
sources that may provide support for special extension functions or 
variables which are not defined in this specification.


See Also:
  • XPathEvaluator
@xsl.usageinternal
/**
 *
 * The class provides an implementation of XPathEvaluator according 
 * to the DOM L3 XPath Specification, Working Group Note 26 February 2004.
 *
 * <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>.</p>
 * 
 * </p>The evaluation of XPath expressions is provided by 
 * <code>XPathEvaluator</code>, which will provide evaluation of XPath 1.0 
 * expressions with no specialized extension functions or variables. It is 
 * expected that the <code>XPathEvaluator</code> interface will be 
 * implemented on the same object which implements the <code>Document</code> 
 * interface in an implementation which supports the XPath DOM module. 
 * <code>XPathEvaluator</code> implementations may be available from other 
 * sources that may provide support for special extension functions or 
 * variables which are not defined in this specification.</p>
 * 
 * @see org.w3c.dom.xpath.XPathEvaluator
 * 
 * @xsl.usage internal
 */
public final class XPathEvaluatorImpl implements XPathEvaluator {

	
This prefix resolver is created whenever null is passed to the 
evaluate method.  Its purpose is to satisfy the DOM L3 XPath API
requirement that if a null prefix resolver is used, an exception 
should only be thrown when an attempt is made to resolve a prefix.

/**
	 * This prefix resolver is created whenever null is passed to the 
	 * evaluate method.  Its purpose is to satisfy the DOM L3 XPath API
	 * requirement that if a null prefix resolver is used, an exception 
	 * should only be thrown when an attempt is made to resolve a prefix.
	 */
	private static class DummyPrefixResolver implements PrefixResolver {

		
Constructor for DummyPrefixResolver.

/**
		 * Constructor for DummyPrefixResolver.
		 */
		DummyPrefixResolver() {}
			
		
Throws:
  • DOMException – 
  NAMESPACE_ERR: Always throws this exceptionn
See Also:
/**
		 * @exception DOMException
    	 *   NAMESPACE_ERR: Always throws this exceptionn
		 *
		 * @see org.apache.xml.utils.PrefixResolver#getNamespaceForPrefix(String, Node)
		 */
		public String getNamespaceForPrefix(String prefix, Node context) {
            String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_NULL_RESOLVER, null);       
            throw new DOMException(DOMException.NAMESPACE_ERR, fmsg);   // Unable to resolve prefix with null prefix resolver.         
		}

		
Throws:
  • DOMException – 
  NAMESPACE_ERR: Always throws this exceptionn
See Also:
/**
		 * @exception DOMException
    	 *   NAMESPACE_ERR: Always throws this exceptionn
    	 * 
		 * @see org.apache.xml.utils.PrefixResolver#getNamespaceForPrefix(String)
		 */
		public String getNamespaceForPrefix(String prefix) {
			return getNamespaceForPrefix(prefix,null);
		}

		
See Also:
  • handlesNullPrefixes.handlesNullPrefixes()
/**
		 * @see org.apache.xml.utils.PrefixResolver#handlesNullPrefixes()
		 */
		public boolean handlesNullPrefixes() {
			return false;
		}

		
See Also:
  • getBaseIdentifier.getBaseIdentifier()
/**
		 * @see org.apache.xml.utils.PrefixResolver#getBaseIdentifier()
		 */
		public String getBaseIdentifier() {
			return null;
		}

	}

    
The document to be searched to parallel the case where the XPathEvaluator
is obtained by casting a Document.

/**
     * The document to be searched to parallel the case where the XPathEvaluator
     * is obtained by casting a Document.
     */  
    private final Document m_doc;
    
    
Constructor for XPathEvaluatorImpl.

Params:
  • doc – The document to be searched, to parallel the case where''
           the XPathEvaluator is obtained by casting the document.
/**
     * Constructor for XPathEvaluatorImpl.
     * 
     * @param doc The document to be searched, to parallel the case where''
     *            the XPathEvaluator is obtained by casting the document.
     */
    public XPathEvaluatorImpl(Document doc) {
        m_doc = doc;
    }
    
    
Constructor in the case that the XPath expression can be evaluated
without needing an XML document at all.

/**
     * Constructor in the case that the XPath expression can be evaluated
     * without needing an XML document at all.
     *
     */
    public XPathEvaluatorImpl() {
            m_doc = null;
    }

	
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 
  prefixes 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 XPathEvaluatori
  • DOMException – 
  NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
  which cannot be resolved by the specified 
  XPathNSResolver.
See Also:
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 
     *   prefixes 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>i
     * @exception DOMException
     *   NAMESPACE_ERR: Raised if the expression contains namespace prefixes 
     *   which cannot be resolved by the specified 
     *   <code>XPathNSResolver</code>.	
     *  
	 * @see org.w3c.dom.xpath.XPathEvaluator#createExpression(String, XPathNSResolver)
	 */
	public XPathExpression createExpression(
		String expression,
		XPathNSResolver resolver)
		throws XPathException, DOMException {
		
		try {
			
			// If the resolver is null, create a dummy prefix resolver
			XPath xpath =  new XPath(expression,null,
			     ((null == resolver) ? new DummyPrefixResolver() : ((PrefixResolver)resolver)), 
			      XPath.SELECT);
                  
            return new XPathExpressionImpl(xpath, m_doc);
			
		} catch (TransformerException e) {
			// Need to pass back exception code DOMException.NAMESPACE_ERR also.
			// Error found in DOM Level 3 XPath Test Suite.
			if(e instanceof XPathStylesheetDOM3Exception)
				throw new DOMException(DOMException.NAMESPACE_ERR,e.getMessageAndLocation());
			else
				throw new XPathException(XPathException.INVALID_EXPRESSION_ERR,e.getMessageAndLocation());
				
		}
	}

	
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.
See Also:
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.
     *  
	 * @see org.w3c.dom.xpath.XPathEvaluator#createNSResolver(Node)
	 */
	public XPathNSResolver createNSResolver(Node nodeResolver) {
	
		return new XPathNSResolverImpl((nodeResolver.getNodeType() == Node.DOCUMENT_NODE)
	           ? ((Document) nodeResolver).getDocumentElement() : 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 
  prefixes 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 coerced to return the specified type relying on 
  XPath type conversions and fail if the desired coercion is not 
  possible. This must be one of the type codes of 
  XPathResult.
  • 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.
See Also:
  • XPathEvaluator.evaluate(String, Node, XPathNSResolver, short, XPathResult)
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 
     *   prefixes 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 coerced to return the specified type relying on 
     *   XPath type conversions and fail if the desired coercion is not 
     *   possible. This must be one of the type codes of 
     *   <code>XPathResult</code>.
     * @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 XPathEvaluator.
     *   <br>NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath 
     *   context node.
	 * 
	 * @see org.w3c.dom.xpath.XPathEvaluator#evaluate(String, Node, XPathNSResolver, short, XPathResult)
	 */
	public Object evaluate(
		String expression,
		Node contextNode,
		XPathNSResolver resolver,
		short type,
		Object result)
		throws XPathException, DOMException {
			
		XPathExpression xpathExpression = createExpression(expression, resolver);
		
		return	xpathExpression.evaluate(contextNode, type, result);
	}

}