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) .
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) .
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) .
|
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.
|
Public Method Summary
abstract XPathExpression | |
abstract Object | |
abstract String | |
abstract Object |
evaluate(String expression, InputSource source, QName returnType)
Evaluate an XPath expression in the context of the specified |
abstract String |
evaluate(String expression, InputSource source)
Evaluate an XPath expression in the context of the specified |
abstract NamespaceContext |
getNamespaceContext()
Return the current namespace context. |
abstract XPathFunctionResolver |
getXPathFunctionResolver()
Return the current function resolver. |
abstract XPathVariableResolver |
getXPathVariableResolver()
Return the current variable resolver. |
abstract void |
reset()
Reset this |
abstract void | |
abstract void | |
abstract void |
Public Methods
public abstract XPathExpression compile (String expression)
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 resolved with the XPathFunctionResolver
.
If expression
is null
, a NullPointerException
is thrown.
Parameters
expression | The XPath expression. |
---|
Returns
- Compiled XPath expression.
Throws
XPathExpressionException | If expression cannot be compiled. |
---|---|
NullPointerException | If expression is null .
|
public abstract Object evaluate (String expression, Object item, QName returnType)
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.
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 | If expression cannot be evaluated. |
---|---|
IllegalArgumentException | If returnType is not one of the types defined in XPathConstants . |
NullPointerException | If expression or returnType is null .
|
public abstract String evaluate (String expression, Object item)
Evaluate an XPath expression in the specified context and return the result as a String
.
This method calls evaluate(String, Object, QName)
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.
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 | If expression cannot be evaluated. |
---|---|
NullPointerException | If expression is null .
|
public abstract Object evaluate (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.
This method builds a data model for the InputSource
and calls
evaluate(String, Object, QName)
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.
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. |
---|---|
IllegalArgumentException | If returnType is not one of the types defined in XPathConstants . |
NullPointerException | If expression , source or returnType
is null .
|
public abstract String evaluate (String expression, InputSource source)
Evaluate an XPath expression in the context of the specified InputSource
and return the result as a String
.
This method calls evaluate(String, InputSource, QName)
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.
Parameters
expression | The XPath expression. |
---|---|
source | The InputSource 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. |
---|---|
NullPointerException | If expression or source is null .
|
public abstract NamespaceContext getNamespaceContext ()
Return the current namespace context.
null
is returned in no namespace context is in effect.
Returns
- Current Namespace context.
public abstract XPathFunctionResolver getXPathFunctionResolver ()
Return the current function resolver.
null
is returned in no function resolver is in effect.
Returns
- Current function resolver.
public abstract XPathVariableResolver getXPathVariableResolver ()
Return the current variable resolver.
null
is returned in no variable resolver is in effect.
Returns
- Current variable resolver.
public abstract 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)
.
It is guaranteed to have a functionally equal XPathFunctionResolver
, XPathVariableResolver
and NamespaceContext
.
public abstract void setNamespaceContext (NamespaceContext nsContext)
Establish a namespace context.
A NullPointerException
is thrown if nsContext
is null
.
Parameters
nsContext | Namespace context to use. |
---|
Throws
NullPointerException | If nsContext is null .
|
---|
public abstract void setXPathFunctionResolver (XPathFunctionResolver resolver)
Establish a function resolver.
A NullPointerException
is thrown if resolver
is null
.
Parameters
resolver | XPath function resolver. |
---|
Throws
NullPointerException | If resolver is null .
|
---|
public abstract void setXPathVariableResolver (XPathVariableResolver resolver)
Establish a variable resolver.
A NullPointerException
is thrown if resolver
is null
.
Parameters
resolver | Variable resolver. |
---|
Throws
NullPointerException | If resolver is null .
|
---|