Class XPathExpressionImpl
- All Implemented Interfaces:
XPathExpression
The JAXP XPathExpression interface represents a compiled XPath expression that can be repeatedly evaluated. This class is Saxon's implementation of that interface.
The class also includes some methods retained from Saxon's original XPath API. When these methods are used, the object contains the context node and other state, so it is not thread-safe.
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Constructor Summary
ConstructorsModifierConstructorDescriptionprotected
XPathExpressionImpl
(Expression exp, Executable exec) The constructor is protected, to ensure that instances can only be created using the compile() method of XPathEvaluator -
Method Summary
Modifier and TypeMethodDescriptionEvaluate the expression to return a string valueJAXP 1.3 evaluate() methodevaluate
(InputSource inputSource) Evaluate the XPath expression against an input source to obtain a string result.evaluate
(InputSource inputSource, QName qName) Evaluate the XPath expression against an input source to obtain a result of a specified typeGet the Configuration under which this XPath expression was compiledLow-level method to get the internal Saxon expression object.Get the stack frame map.protected void
Define the number of slots needed for local variables within the expression.Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
Methods inherited from interface javax.xml.xpath.XPathExpression
evaluateExpression, evaluateExpression, evaluateExpression, evaluateExpression
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Constructor Details
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XPathExpressionImpl
The constructor is protected, to ensure that instances can only be created using the compile() method of XPathEvaluator- Parameters:
exp
- the compiled expressionexec
- the executable
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Method Details
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setStackFrameMap
Define the number of slots needed for local variables within the expression. This method is for internal use only.- Parameters:
map
- description of the stack frame
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getStackFrameMap
Get the stack frame map. This holds information about the allocation of slots to variables. This is needed by applications using low-level interfaces for evaluating the expression- Returns:
- a description of the stack frame
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getConfiguration
Get the Configuration under which this XPath expression was compiled- Returns:
- the Saxon configuration
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evaluate
JAXP 1.3 evaluate() method- Specified by:
evaluate
in interfaceXPathExpression
- Parameters:
node
- The context node: generalized in Saxon to allow any XDM item to act as the context item.The types of values accepted, and the conversions applied, are described in the Saxon documentation.
Contrary to the interface specification, Saxon does not supply an empty document when the value is null. This is because XPath 2.0 allows the context item to be "absent" (null). So Saxon executes the XPath expression with the context item undefined.
qName
- Indicates the type of result required. This must be one of the constants defined in the JAXPXPathConstants
class. Saxon will attempt to convert the actual result of the expression to the required type using the XPath 1.0 conversion rules.- Returns:
- the result of the evaluation, as a Java object of the appropriate type. Saxon interprets the
rules as follows:
Return value types QName Return Value BOOLEAN The effective boolean value of the actual result, as a Java Boolean object STRING The result of applying the string() function to the actual result, as a Java String object NUMBER The result of applying the number() function to the actual result, as a Java Double object NODE A single node, in the native data model supplied as input. If the expression returns more than one node, the first is returned. If the expression returns an empty sequence, null is returned. If the expression returns an atomic value, or if the first item in the result sequence is an atomic value, an exception is thrown. NODESET This is interpreted as allowing any sequence, of nodes or atomic values. If the first argument is a wrapper around a DOM Node, then the result is returned as a DOM NodeList, and an exception is then thrown if the result sequence contains a value that is not a DOM Node. In all other cases the result is returned as a Java List object, unless it is empty, in which case null is returned. The contents of the list may be node objects (in the native data model supplied as input), or Java objects representing the XPath atomic values in the actual result: String for an xs:string, Double for a xs:double, Long for an xs:integer, and so on. (For safety, cast the values to a type such as xs:string within the XPath expression). - Throws:
XPathExpressionException
- if evaluation of the expression fails or if the result cannot be converted to the requested type.
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evaluate
Evaluate the expression to return a string value- Specified by:
evaluate
in interfaceXPathExpression
- Parameters:
node
- The context node: generalized in Saxon to allow any XDM item to act as the context item.The types of values accepted, and the conversions applied, are described in the Saxon documentation.
Contrary to the interface specification, Saxon does not supply an empty document when the value is null. This is because XPath 2.0 allows the context item to be "absent" (null). So Saxon executes the XPath expression with the context item undefined.
- Returns:
- the results of the expression, converted to a String
- Throws:
XPathExpressionException
- if evaluation fails
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evaluate
Evaluate the XPath expression against an input source to obtain a result of a specified type- Specified by:
evaluate
in interfaceXPathExpression
- Parameters:
inputSource
- The input source document against which the expression is evaluated.If any error occurs reading or parsing this document, the error is notified to the
ErrorListener
registered with theConfiguration
, and also causes an exception to be thrown.(Note that there is no caching. This will be parsed, and the parsed result will be discarded.)
If the supplied value is null then (contrary to the JAXP specifications), the XPath expression is evaluated with the context item undefined.
qName
- The type required, identified by a constant inXPathConstants
- Returns:
- the result of the evaluation, as a Java object of the appropriate type:
see
evaluate(Object, javax.xml.namespace.QName)
- Throws:
XPathExpressionException
- if an error is detected
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evaluate
Evaluate the XPath expression against an input source to obtain a string result.- Specified by:
evaluate
in interfaceXPathExpression
- Parameters:
inputSource
- The input source document against which the expression is evaluated.If any error occurs reading or parsing this document, the error is notified to the
ErrorListener
registered with theConfiguration
, and also causes an exception to be thrown.(Note that there is no caching. This will be parsed, and the parsed result will be discarded.)
If the supplied value is null then (contrary to the JAXP specifications), the XPath expression is evaluated with the context item undefined.
- Returns:
- the result of the evaluation, converted to a String
- Throws:
XPathExpressionException
- in the event of an XPath dynamic errorNullPointerException
- IfinputSource
isnull
.
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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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