Package net.sf.saxon.sxpath
Class XPathExpression
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- net.sf.saxon.sxpath.XPathExpression
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public class XPathExpression extends java.lang.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
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Constructor Summary
Constructors Modifier Constructor Description protected
XPathExpression(XPathEvaluator evaluator, Expression exp)
The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description XPathContext
createDynamicContext(Item contextItem)
Create a dynamic context suitable for evaluating this expressionjava.util.List
evaluate(javax.xml.transform.Source source)
Execute a prepared XPath expression, returning the results as a List.java.lang.Object
evaluateSingle(javax.xml.transform.Source source)
Execute a prepared XPath expression, returning the first item in the result.Expression
getInternalExpression()
Low-level method to get the internal Saxon expression object.SequenceIterator
rawIterator(javax.xml.transform.Source source)
Get a raw iterator over the results of the expression.protected void
setStackFrameMap(SlotManager map)
Define the number of slots needed for local variables within the expression
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Constructor Detail
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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
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Method Detail
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setStackFrameMap
protected void setStackFrameMap(SlotManager map)
Define the number of slots needed for local variables within the expression
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createDynamicContext
public XPathContext createDynamicContext(Item contextItem)
Create a dynamic context suitable for evaluating this expression- Parameters:
contextItem
- the initial context item- Returns:
- an XPathContext object representing a suitable dynamic context. This will be initialized with a stack frame suitable for holding the variables used by the expression.
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evaluate
public java.util.List evaluate(javax.xml.transform.Source source) throws XPathException
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.
- Throws:
XPathException
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evaluateSingle
public java.lang.Object evaluateSingle(javax.xml.transform.Source source) throws XPathException
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
- Throws:
XPathException
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rawIterator
public SequenceIterator rawIterator(javax.xml.transform.Source source) throws XPathException
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.- Throws:
XPathException
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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.
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