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public interface XPathExpression
XPathExpression
provides access to compiled XPath expressions.Evaluation of XPath Expressions. context If a request is made to evaluate the expression in the absence of a context item, an empty document node will be used for the context. For the purposes of evaluating XPath expressions, a DocumentFragment is treated like a Document node. variables If the expression contains a variable reference, its value will be found through the XPathVariableResolver
. AnXPathExpressionException
is raised if the variable resolver is undefined or the resolver returnsnull
for the variable. The value of a variable must be immutable through the course of any single evaluation.functions If the expression contains a function reference, the function will be found through the XPathFunctionResolver
. AnXPathExpressionException
is raised if the function resolver is undefined or the function resolver returnsnull
for the function.QNames QNames in the expression are resolved against the XPath namespace context. result This result of evaluating an expression is converted to an instance of the desired return type. Valid return types are defined in XPathConstants
. Conversion to the return type follows XPath conversion rules.An XPath expression is not thread-safe and not reentrant. In other words, it is the application's responsibility to make sure that one
XPathExpression
object is not used from more than one thread at any given time, and while theevaluate
method is invoked, applications may not recursively call theevaluate
method.- Since:
- 1.5
- See Also:
- XML Path Language (XPath) Version 1.0, Expressions
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Method Summary
Methods Modifier and Type Method and Description String
evaluate(InputSource source)
Evaluate the compiled XPath expression in the context of the specifiedInputSource
and return the result as aString
.Object
evaluate(InputSource source, QName returnType)
Evaluate the compiled XPath expression in the context of the specifiedInputSource
and return the result as the specified type.String
evaluate(Object item)
Evaluate the compiled XPath expression in the specified context and return the result as aString
.Object
evaluate(Object item, QName returnType)
Evaluate the compiled XPath expression in the specified context and return the result as the specified type.
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Method Detail
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evaluate
Object evaluate(Object item, QName returnType) throws XPathExpressionException
Evaluate the compiled XPath expression in the specified context and return the result as the specified type.
See Evaluation of XPath Expressions for context item evaluation, variable, function and QName resolution and return type conversion.
If
returnType
is not one of the types defined inXPathConstants
, then anIllegalArgumentException
is thrown.If a
null
value is provided foritem
, an empty document will be used for the context. IfreturnType
isnull
, then aNullPointerException
is thrown.- Parameters:
item
- The starting context (a node, for example).returnType
- The desired return type.- Returns:
- The
Object
that is the result of evaluating the expression and converting the result toreturnType
. - Throws:
XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- IfreturnType
is not one of the types defined inXPathConstants
.NullPointerException
- IfreturnType
isnull
.
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evaluate
String evaluate(Object item) throws XPathExpressionException
Evaluate the compiled XPath expression in the specified context and return the result as a
String
.This method calls
evaluate(Object item, QName returnType)
with areturnType
ofXPathConstants.STRING
.See Evaluation of XPath Expressions for context item evaluation, variable, function and QName resolution and return type conversion.
If a
null
value is provided foritem
, an empty document will be used for the context.- Parameters:
item
- The starting context (a node, for example).- Returns:
- The
String
that is the result of evaluating the expression and converting the result to aString
. - Throws:
XPathExpressionException
- If the expression cannot be evaluated.
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evaluate
Object evaluate(InputSource source, QName returnType) throws XPathExpressionException
Evaluate the compiled XPath expression in the context of the specified
InputSource
and return the result as the specified type.This method builds a data model for the
InputSource
and callsevaluate(Object item, QName returnType)
on the resulting document object.See Evaluation of XPath Expressions for context item evaluation, variable, function and QName resolution and return type conversion.
If
returnType
is not one of the types defined inXPathConstants
, then anIllegalArgumentException
is thrown.If
source
orreturnType
isnull
, then aNullPointerException
is thrown.- Parameters:
source
- TheInputSource
of the document to evaluate over.returnType
- The desired return type.- Returns:
- The
Object
that is the result of evaluating the expression and converting the result toreturnType
. - Throws:
XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- IfreturnType
is not one of the types defined inXPathConstants
.NullPointerException
- Ifsource
orreturnType
isnull
.
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evaluate
String evaluate(InputSource source) throws XPathExpressionException
Evaluate the compiled XPath expression in the context of the specified
InputSource
and return the result as aString
.This method calls
evaluate(InputSource source, QName returnType)
with areturnType
ofXPathConstants.STRING
.See Evaluation of XPath Expressions for context item evaluation, variable, function and QName resolution and return type conversion.
If
source
isnull
, then aNullPointerException
is thrown.- Parameters:
source
- TheInputSource
of the document to evaluate over.- Returns:
- The
String
that is the result of evaluating the expression and converting the result to aString
. - Throws:
XPathExpressionException
- If the expression cannot be evaluated.NullPointerException
- Ifsource
isnull
.
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Document created the 11/06/2005, last modified the 04/03/2020
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