Package net.sf.saxon.sxpath
Class XPathExpression
- java.lang.Object
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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 theXPathEvaluator
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 Deprecated Methods Modifier and Type Method Description XPathDynamicContext
createDynamicContext(Item contextItem)
Create a dynamic context suitable for evaluating this expressionboolean
effectiveBooleanValue(XPathDynamicContext context)
Evaluate the expression, returning its effective boolean valuejava.util.List
evaluate(javax.xml.transform.Source source)
Execute a prepared XPath expression, returning the results as a List in which items have been converted to the appropriate Java object.java.util.List
evaluate(XPathDynamicContext context)
Execute the expression, returning the result as a List, whose members will be instances of the classItem
java.lang.Object
evaluateSingle(javax.xml.transform.Source source)
Execute a prepared XPath expression, returning the first item in the result.Item
evaluateSingle(XPathDynamicContext context)
Execute the expression, returning the result as a singleItem
If the result of the expression is a sequence containing more than one item, items after the first are discarded.Expression
getInternalExpression()
Low-level method to get the internal Saxon expression object.SequenceIterator
iterate(XPathDynamicContext context)
Execute the expression, returning the result as aSequenceIterator
, whose members will be instances of the classItem
SequenceIterator
rawIterator(javax.xml.transform.Source source)
Deprecated.since 8.9 - useiterate(net.sf.saxon.sxpath.XPathDynamicContext)
protected void
setStackFrameMap(SlotManager map, int numberOfExternalVariables)
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- Parameters:
evaluator
- the creating XPathEvaluatorexp
- the internal representation of the compiled expression
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Method Detail
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setStackFrameMap
protected void setStackFrameMap(SlotManager map, int numberOfExternalVariables)
Define the number of slots needed for local variables within the expression- Parameters:
map
- the stack frame map identifying all the variables used by the expression, both those declared internally, and references to variables declared externallynumberOfExternalVariables
- the number of slots in the stack frame allocated to externally-declared variables. These must be assigned a value before execution starts
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createDynamicContext
public XPathDynamicContext createDynamicContext(Item contextItem)
Create a dynamic context suitable for evaluating this expression- Parameters:
contextItem
- the initial context item, which may be null if no context item is required, or if it is to be supplied later- Returns:
- an XPathDynamicContext 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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iterate
public SequenceIterator iterate(XPathDynamicContext context) throws XPathException
Execute the expression, returning the result as aSequenceIterator
, whose members will be instances of the classItem
Note that if evaluation of the expression fails with a dynamic error, this will generally be reported in the form of an exception thrown by the next() method of the
SequenceIterator
- Parameters:
context
- the XPath dynamic context- Returns:
- an iterator over the result of the expression
- Throws:
XPathException
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evaluate
public java.util.List evaluate(XPathDynamicContext context) throws XPathException
Execute the expression, returning the result as a List, whose members will be instances of the classItem
- Parameters:
context
- the XPath dynamic context- Returns:
- a list of items representing the result of the expression
- Throws:
XPathException
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evaluateSingle
public Item evaluateSingle(XPathDynamicContext context) throws XPathException
Execute the expression, returning the result as a singleItem
If the result of the expression is a sequence containing more than one item, items after the first are discarded. If the result is an empty sequence, the method returns null.- Parameters:
context
- the XPath dynamic context- Returns:
- the first item in the result of the expression, or null
- Throws:
XPathException
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effectiveBooleanValue
public boolean effectiveBooleanValue(XPathDynamicContext context) throws XPathException
Evaluate the expression, returning its effective boolean value- Parameters:
context
- the XPath dynamic context- Returns:
- the effective boolean value of the result, as defined by the fn:boolean() function
- Throws:
XPathException
- if a dynamic error occurs, or if the result is a value for which no effective boolean value is defined
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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 in which items have been converted to the appropriate Java object.- 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. For the way in which the source document is built, seeConfiguration.buildDocument(javax.xml.transform.Source)
- 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. For the way in which the source document is built, seeConfiguration.buildDocument(javax.xml.transform.Source)
- 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
Deprecated.since 8.9 - useiterate(net.sf.saxon.sxpath.XPathDynamicContext)
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. For the way in which the source document is built, seeConfiguration.buildDocument(javax.xml.transform.Source)
- Returns:
- an iterator over the results of the expression
- 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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