Interface XPath
XPath
provides access to the XPath evaluation environment and 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
set with setXPathVariableResolver(XPathVariableResolver resolver) .
An XPathExpressionException is raised if the variable resolver is undefined or
the resolver returns null 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
set with setXPathFunctionResolver(XPathFunctionResolver resolver) .
An XPathExpressionException is raised if the function resolver is undefined or
the function resolver returns null for the function.
|
QNames |
QNames in the expression are resolved against the XPath namespace context
set with setNamespaceContext(NamespaceContext nsContext) .
|
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.
|
- Since:
- 1.5
- Version:
- $Revision: 569998 $, $Date: 2007-08-27 07:40:02 +0300 (Mon, 27 Aug 2007) $
- Author:
- Norman Walsh, Jeff Suttor
- See Also:
-
Method Summary
Modifier and TypeMethodDescriptioncompile
(java.lang.String expression) Compile an XPath expression for later evaluation.java.lang.String
evaluate
(java.lang.String expression, java.lang.Object item) Evaluate an XPath expression in the specified context and return the result as aString
.java.lang.Object
Evaluate anXPath
expression in the specified context and return the result as the specified type.java.lang.String
evaluate
(java.lang.String expression, InputSource source) Evaluate an XPath expression in the context of the specifiedInputSource
and return the result as aString
.java.lang.Object
evaluate
(java.lang.String expression, InputSource source, QName returnType) Evaluate an XPath expression in the context of the specifiedInputSource
and return the result as the specified type.Return the current namespace context.Return the current function resolver.Return the current variable resolver.void
reset()
Reset thisXPath
to its original configuration.void
setNamespaceContext
(NamespaceContext nsContext) Establish a namespace context.void
Establish a function resolver.void
Establish a variable resolver.
-
Method Details
-
reset
void reset()Reset this
XPath
to its original configuration.XPath
is reset to the same state as when it was created withXPathFactory.newXPath()
.reset()
is designed to allow the reuse of existingXPath
s thus saving resources associated with the creation of newXPath
s.The reset
XPath
is not guaranteed to have the sameXPathFunctionResolver
,XPathVariableResolver
orNamespaceContext
Object
s, e.g.Object.equals(Object obj)
. It is guaranteed to have a functionally equalXPathFunctionResolver
,XPathVariableResolver
andNamespaceContext
. -
setXPathVariableResolver
Establish a variable resolver.
A
NullPointerException
is thrown ifresolver
isnull
.- Parameters:
resolver
- Variable resolver.- Throws:
java.lang.NullPointerException
- Ifresolver
isnull
.
-
getXPathVariableResolver
XPathVariableResolver getXPathVariableResolver()Return the current variable resolver.
null
is returned in no variable resolver is in effect.- Returns:
- Current variable resolver.
-
setXPathFunctionResolver
Establish a function resolver.
A
NullPointerException
is thrown ifresolver
isnull
.- Parameters:
resolver
- XPath function resolver.- Throws:
java.lang.NullPointerException
- Ifresolver
isnull
.
-
getXPathFunctionResolver
XPathFunctionResolver getXPathFunctionResolver()Return the current function resolver.
null
is returned in no function resolver is in effect.- Returns:
- Current function resolver.
-
setNamespaceContext
Establish a namespace context.
A
NullPointerException
is thrown ifnsContext
isnull
.- Parameters:
nsContext
- Namespace context to use.- Throws:
java.lang.NullPointerException
- IfnsContext
isnull
.
-
getNamespaceContext
NamespaceContext getNamespaceContext()Return the current namespace context.
null
is returned in no namespace context is in effect.- Returns:
- Current Namespace context.
-
compile
Compile an XPath expression for later evaluation.
If
expression
contains anyXPathFunction
s, they must be available via theXPathFunctionResolver
. AnXPathExpressionException
will be thrown if theXPathFunction
cannot be resolved with theXPathFunctionResolver
.If
expression
isnull
, aNullPointerException
is thrown.- Parameters:
expression
- The XPath expression.- Returns:
- Compiled XPath expression.
- Throws:
XPathExpressionException
- Ifexpression
cannot be compiled.java.lang.NullPointerException
- Ifexpression
isnull
.
-
evaluate
java.lang.Object evaluate(java.lang.String expression, java.lang.Object item, QName returnType) throws XPathExpressionException Evaluate an
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
(NUMBER
,STRING
,BOOLEAN
,NODE
orNODESET
) then anIllegalArgumentException
is thrown.If a
null
value is provided foritem
, an empty document will be used for the context. Ifexpression
orreturnType
isnull
, then aNullPointerException
is thrown.- Parameters:
expression
- The XPath expression.item
- The starting context (node or node list, for example).returnType
- The desired return type.- Returns:
- Result of evaluating an XPath expression as an
Object
ofreturnType
. - Throws:
XPathExpressionException
- Ifexpression
cannot be evaluated.java.lang.IllegalArgumentException
- IfreturnType
is not one of the types defined inXPathConstants
.java.lang.NullPointerException
- Ifexpression
orreturnType
isnull
.
-
evaluate
java.lang.String evaluate(java.lang.String expression, java.lang.Object item) throws XPathExpressionException Evaluate an XPath expression in the specified context and return the result as a
String
.This method calls
evaluate(String expression, 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. Ifexpression
isnull
, then aNullPointerException
is thrown.- Parameters:
expression
- The XPath expression.item
- The starting context (node or node list, for example).- Returns:
- The
String
that is the result of evaluating the expression and converting the result to aString
. - Throws:
XPathExpressionException
- Ifexpression
cannot be evaluated.java.lang.NullPointerException
- Ifexpression
isnull
.
-
evaluate
java.lang.Object evaluate(java.lang.String expression, InputSource source, QName returnType) throws XPathExpressionException Evaluate an 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(String expression, 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
expression
,source
orreturnType
isnull
, then aNullPointerException
is thrown.- Parameters:
expression
- The XPath expression.source
- The input source of the document to evaluate over.returnType
- The desired return type.- Returns:
- The
Object
that encapsulates the result of evaluating the expression. - Throws:
XPathExpressionException
- If expression cannot be evaluated.java.lang.IllegalArgumentException
- IfreturnType
is not one of the types defined inXPathConstants
.java.lang.NullPointerException
- Ifexpression
,source
orreturnType
isnull
.
-
evaluate
java.lang.String evaluate(java.lang.String expression, InputSource source) throws XPathExpressionException Evaluate an XPath expression in the context of the specified
InputSource
and return the result as aString
.This method calls
evaluate(String expression, 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
expression
orsource
isnull
, then aNullPointerException
is thrown.- Parameters:
expression
- The XPath expression.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 expression cannot be evaluated.java.lang.NullPointerException
- Ifexpression
orsource
isnull
.
-