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public 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.
|
Method Summary | |
---|---|
XPathExpression |
compile(java.lang.String expression)
Compile an XPath expression for later evaluation. |
java.lang.String |
evaluate(java.lang.String expression,
InputSource source)
Evaluate an XPath expression in the context of the specified InputSource
and return the result as a String . |
java.lang.Object |
evaluate(java.lang.String expression,
InputSource source,
QName returnType)
Evaluate an XPath expression in the context of the specified InputSource
and return the result as the specified type. |
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 a String . |
java.lang.Object |
evaluate(java.lang.String expression,
java.lang.Object item,
QName returnType)
Evaluate an XPath expression in the specified context and return the result as the specified type. |
NamespaceContext |
getNamespaceContext()
Return the current namespace context. |
XPathFunctionResolver |
getXPathFunctionResolver()
Return the current function resolver. |
XPathVariableResolver |
getXPathVariableResolver()
Return the current variable resolver. |
void |
reset()
Reset this XPath to its original configuration. |
void |
setNamespaceContext(NamespaceContext nsContext)
Establish a namespace context. |
void |
setXPathFunctionResolver(XPathFunctionResolver resolver)
Establish a function resolver. |
void |
setXPathVariableResolver(XPathVariableResolver resolver)
Establish a variable resolver. |
Method Detail |
---|
void reset()
Reset this XPath
to its original configuration.
XPath
is reset to the same state as when it was created with
XPathFactory.newXPath()
.
reset()
is designed to allow the reuse of existing XPath
s
thus saving resources associated with the creation of new XPath
s.
The reset XPath
is not guaranteed to have the same XPathFunctionResolver
, XPathVariableResolver
or NamespaceContext
Object
s, e.g. Object.equals(Object obj)
.
It is guaranteed to have a functionally equal XPathFunctionResolver
, XPathVariableResolver
and NamespaceContext
.
void setXPathVariableResolver(XPathVariableResolver resolver)
Establish a variable resolver.
A NullPointerException
is thrown if resolver
is null
.
resolver
- Variable resolver.
java.lang.NullPointerException
- If resolver
is null
.XPathVariableResolver getXPathVariableResolver()
Return the current variable resolver.
null
is returned in no variable resolver is in effect.
void setXPathFunctionResolver(XPathFunctionResolver resolver)
Establish a function resolver.
A NullPointerException
is thrown if resolver
is null
.
resolver
- XPath function resolver.
java.lang.NullPointerException
- If resolver
is null
.XPathFunctionResolver getXPathFunctionResolver()
Return the current function resolver.
null
is returned in no function resolver is in effect.
void setNamespaceContext(NamespaceContext nsContext)
Establish a namespace context.
A NullPointerException
is thrown if nsContext
is null
.
nsContext
- Namespace context to use.
java.lang.NullPointerException
- If nsContext
is null
.NamespaceContext getNamespaceContext()
Return the current namespace context.
null
is returned in no namespace context is in effect.
XPathExpression compile(java.lang.String expression) throws XPathExpressionException
Compile an XPath expression for later evaluation.
If expression
contains any XPathFunction
s,
they must be available via the XPathFunctionResolver
.
An XPathExpressionException
will be thrown if the XPathFunction
cannot be resovled with the XPathFunctionResolver
.
If expression
is null
, a NullPointerException
is thrown.
expression
- The XPath expression.
XPathExpressionException
- If expression
cannot be compiled.
java.lang.NullPointerException
- If expression
is null
.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 in XPathConstants
(
NUMBER
,
STRING
,
BOOLEAN
,
NODE
or
NODESET
)
then an IllegalArgumentException
is thrown.
If a null
value is provided for
item
, an empty document will be used for the
context.
If expression
or returnType
is null
, then a
NullPointerException
is thrown.
expression
- The XPath expression.item
- The starting context (node or node list, for example).returnType
- The desired return type.
Object
of returnType
.
XPathExpressionException
- If expression
cannot be evaluated.
java.lang.IllegalArgumentException
- If returnType
is not one of the types defined in XPathConstants
.
java.lang.NullPointerException
- If expression
or returnType
is null
.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 a returnType
of
XPathConstants.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 for
item
, an empty document will be used for the
context.
If expression
is null
, then a NullPointerException
is thrown.
expression
- The XPath expression.item
- The starting context (node or node list, for example).
String
that is the result of evaluating the expression and
converting the result to a String
.
XPathExpressionException
- If expression
cannot be evaluated.
java.lang.NullPointerException
- If expression
is null
.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 calls
evaluate(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 in XPathConstants
,
then an IllegalArgumentException
is thrown.
If expression
, source
or returnType
is null
,
then a NullPointerException
is thrown.
expression
- The XPath expression.source
- The input source of the document to evaluate over.returnType
- The desired return type.
Object
that encapsulates the result of evaluating the expression.
XPathExpressionException
- If expression cannot be evaluated.
java.lang.IllegalArgumentException
- If returnType
is not one of the types defined in XPathConstants
.
java.lang.NullPointerException
- If expression
, source
or returnType
is null
.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 a String
.
This method calls evaluate(String expression, InputSource source, QName returnType)
with a
returnType
of XPathConstants.STRING
.
See Evaluation of XPath Expressions for context item evaluation, variable, function and QName resolution and return type conversion.
If expression
or source
is null
,
then a NullPointerException
is thrown.
expression
- The XPath expression.source
- The InputSource
of the document to evaluate over.
String
that is the result of evaluating the expression and
converting the result to a String
.
XPathExpressionException
- If expression cannot be evaluated.
java.lang.NullPointerException
- If expression
or source
is null
.
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