Package net.sf.saxon.sxpath
Class XPathExpression
java.lang.Object
net.sf.saxon.sxpath.XPathExpression
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
ConstructorsModifierConstructorDescriptionprotected
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
Modifier and TypeMethodDescriptioncreateDynamicContext
(Item contextItem) Create a dynamic context suitable for evaluating this expressionExecute a prepared XPath expression, returning the results as a List.evaluateSingle
(Source source) Execute a prepared XPath expression, returning the first item in the result.Low-level method to get the internal Saxon expression object.rawIterator
(Source source) Get a raw iterator over the results of the expression.protected void
Define the number of slots needed for local variables within the expression
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Constructor Details
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XPathExpression
The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator
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Method Details
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setStackFrameMap
Define the number of slots needed for local variables within the expression -
createDynamicContext
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
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
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
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
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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