net.sf.saxon.sxpath

Class XPathExpression

public class XPathExpression extends Object

This class is a representation of an XPath Expression for use with the XPathEvaluator class. It is modelled on the XPath API defined in JAXP 1.3, but is cut down to remove any dependencies on JAXP 1.3, making it suitable for use on vanilla JDK 1.4 installations.

Author: Michael H. Kay

Constructor Summary
protected XPathExpression(XPathEvaluator evaluator, Expression exp)
The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator
Method Summary
Listevaluate(Source source)
Execute a prepared XPath expression, returning the results as a List.
ObjectevaluateSingle(Source source)
Execute a prepared XPath expression, returning the first item in the result.
ExpressiongetInternalExpression()
Low-level method to get the internal Saxon expression object.
SequenceIteratorrawIterator(Source source)
Get a raw iterator over the results of the expression.
protected voidsetStackFrameMap(SlotManager map)
Define the number of slots needed for local variables within the expression

Constructor Detail

XPathExpression

protected XPathExpression(XPathEvaluator evaluator, Expression exp)
The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator

Method Detail

evaluate

public List evaluate(Source source)
Execute a prepared XPath expression, returning the results as a List.

Parameters: source the document or other node against which the XPath expression will be evaluated. This may be a Saxon NodeInfo object, representing a node in an existing tree, or it may be any kind of JAXP Source object such as a StreamSource SAXSource or DOMSource.

Returns: The results of the expression, as a List. The List represents the sequence of items returned by the expression. Each item in the list will either be an instance of net.sf.saxon.om.NodeInfo, representing a node, or a Java object representing an atomic value.

evaluateSingle

public Object evaluateSingle(Source source)
Execute a prepared XPath expression, returning the first item in the result. This is useful where it is known that the expression will only return a singleton value (for example, a single node, or a boolean).

Parameters: source the document or other node against which the XPath expression will be evaluated. This may be a Saxon NodeInfo object, representing a node in an existing tree, or it may be any kind of JAXP Source object such as a StreamSource SAXSource or DOMSource.

Returns: The first item in the sequence returned by the expression. If the expression returns an empty sequence, this method returns null. Otherwise, it returns the first item in the result sequence, represented as a Java object using the same mapping as for the evaluate() method

getInternalExpression

public Expression getInternalExpression()
Low-level method to get the internal Saxon expression object. This exposes a wide range of internal methods that may be needed by specialized applications, and allows greater control over the dynamic context for evaluating the expression.

Returns: the underlying Saxon expression object.

rawIterator

public SequenceIterator rawIterator(Source source)
Get a raw iterator over the results of the expression. This returns results without any conversion of the returned items to "native" Java classes. This method is intended for use by applications that need to process the results of the expression using internal Saxon interfaces.

Parameters: source the document or other node against which the XPath expression will be evaluated. This may be a Saxon NodeInfo object, representing a node in an existing tree, or it may be any kind of JAXP Source object such as a StreamSource SAXSource or DOMSource.

setStackFrameMap

protected void setStackFrameMap(SlotManager map)
Define the number of slots needed for local variables within the expression