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XPathExpressionImpl.javaAPI DocJava SE 6 API7942Tue Jun 10 00:23:14 BST 2008com.sun.org.apache.xpath.internal.domapi

XPathExpressionImpl

public class XPathExpressionImpl extends Object implements XPathExpression
The class provides an implementation of XPathExpression 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 XPathExpression interface represents a parsed and resolved XPath expression.

see
org.w3c.dom.xpath.XPathExpression
xsl.usage
internal

Fields Summary
private final XPath
m_xpath
The xpath object that this expression wraps
private final Document
m_doc
The document to be searched to parallel the case where the XPathEvaluator is obtained by casting a Document.
Constructors Summary
XPathExpressionImpl(XPath xpath, Document doc)
Constructor for XPathExpressionImpl.

param
xpath The wrapped XPath object.
param
doc The document to be searched, to parallel the case where'' the XPathEvaluator is obtained by casting the document.

        m_xpath = xpath;
        m_doc = doc;
Methods Summary
public java.lang.Objectevaluate(org.w3c.dom.Node contextNode, short type, java.lang.Object result)
This method provides an implementation XPathResult.evaluate according to the DOM L3 XPath Specification, Working Group Note 26 February 2004.

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

Evaluates this XPath expression and returns a result.

param
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.
param
type If a specific type is specified, then the result will be coerced to return the specified type relying on XPath conversions and fail if the desired coercion is not possible. This must be one of the type codes of XPathResult.
param
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.
return
The result of the evaluation of the XPath expression.For XPath 1.0 results, this object will be of type XPathResult.
exception
XPathException TYPE_ERR: Raised if the result cannot be converted to return the specified type.
exception
DOMException WRONG_DOCUMENT_ERR: The Node is from a document that is not supported by the XPathEvaluator that created this XPathExpression.
NOT_SUPPORTED_ERR: The Node is not a type permitted as an XPath context node.
see
org.w3c.dom.xpath.XPathExpression#evaluate(Node, short, XPathResult)
xsl.usage
internal

            
        // If the XPathEvaluator was determined by "casting" the document    
        if (m_doc != null) {
        
            // Check that the context node is owned by the same document
            if ((contextNode != m_doc) && (!contextNode.getOwnerDocument().equals(m_doc))) {
                String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_DOCUMENT, null);       
                throw new DOMException(DOMException.WRONG_DOCUMENT_ERR, fmsg);
            }
            
            // Check that the context node is an acceptable node type
            short nodeType = contextNode.getNodeType();
            if ((nodeType != Document.DOCUMENT_NODE) &&
                (nodeType != Document.ELEMENT_NODE) && 
                (nodeType != Document.ATTRIBUTE_NODE) &&
                (nodeType != Document.TEXT_NODE) &&
                (nodeType != Document.CDATA_SECTION_NODE) &&
                (nodeType != Document.COMMENT_NODE) &&
                (nodeType != Document.PROCESSING_INSTRUCTION_NODE) &&
                (nodeType != XPathNamespace.XPATH_NAMESPACE_NODE)) {
                    String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_WRONG_NODETYPE, null);       
                    throw new DOMException(DOMException.NOT_SUPPORTED_ERR, fmsg);
            }
        }
            
        //     
        // If the type is not a supported type, throw an exception and be
        // done with it!
        if (!XPathResultImpl.isValidType(type)) {
            String fmsg = XPATHMessages.createXPATHMessage(XPATHErrorResources.ER_INVALID_XPATH_TYPE, new Object[] {new Integer(type)});       
            throw new XPathException(XPathException.TYPE_ERR,fmsg); // Invalid XPath type argument: {0}               
        }
        
        // Cache xpath context?
        XPathContext xpathSupport = new XPathContext();
        
        // if m_document is not null, build the DTM from the document 
        if (null != m_doc) {
            xpathSupport.getDTMHandleFromNode(m_doc);
        }

        XObject xobj = null;
        try {
            xobj = m_xpath.execute(xpathSupport, contextNode, null);         
        } catch (TransformerException te) {
            // What should we do here?
            throw new XPathException(XPathException.INVALID_EXPRESSION_ERR,te.getMessageAndLocation()); 
        }

        // Create a new XPathResult object
        // Reuse result object passed in?
        // The constructor will check the compatibility of type and xobj and
        // throw an exception if they are not compatible.
        return new XPathResultImpl(type,xobj,contextNode, m_xpath);