public
interface
XPath
| javax.xml.xpath.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).
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.
|
See also:
Public methods | |
|---|---|
abstract
XPathExpression
|
compile(String expression)
Compile an XPath expression for later evaluation. |
abstract
Object
|
evaluate(String expression, Object item, QName returnType)
Evaluate an |
abstract
String
|
evaluate(String expression, Object item)
Evaluate an XPath expression in the specified context and return the result as a |
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
|
setNamespaceContext(NamespaceContext nsContext)
Establish a namespace context. |
abstract
void
|
setXPathFunctionResolver(XPathFunctionResolver resolver)
Establish a function resolver. |
abstract
void
|
setXPathVariableResolver(XPathVariableResolver resolver)
Establish a variable resolver. |
XPathExpression compile (String expression)
Compile an XPath expression for later evaluation.
If expression contains any XPathFunctions,
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 |
String:
The XPath expression. |
| Returns | |
|---|---|
XPathExpression |
Compiled XPath expression. |
| Throws | |
|---|---|
XPathExpressionException |
If expression cannot be compiled. |
NullPointerException |
If expression is null.
|
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 |
String:
The XPath expression. |
item |
Object:
The starting context (node or node list, for example). |
returnType |
QName:
The desired return type. |
| Returns | |
|---|---|
Object |
Result of evaluating an XPath expression as an Object of returnType. |
| 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.
|
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
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 |
String:
The XPath expression. |
item |
Object:
The starting context (node or node list, for example). |
| Returns | |
|---|---|
String |
The String that is the result of evaluating the expression and
converting the result to a String. |
| Throws | |
|---|---|
XPathExpressionException |
If expression cannot be evaluated. |
NullPointerException |
If expression is null.
|
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 |
String:
The XPath expression. |
source |
InputSource:
The input source of the document to evaluate over. |
returnType |
QName:
The desired return type. |
| Returns | |
|---|---|
Object |
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.
|
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 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 |
String:
The XPath expression. |
source |
InputSource:
The InputSource of the document to evaluate over. |
| Returns | |
|---|---|
String |
The String that is the result of evaluating the expression and
converting the result to a String. |
| Throws | |
|---|---|
XPathExpressionException |
If expression cannot be evaluated. |
NullPointerException |
If expression or source is null.
|
NamespaceContext getNamespaceContext ()
Return the current namespace context.
null is returned in no namespace context is in effect.
| Returns | |
|---|---|
NamespaceContext |
Current Namespace context. |
XPathFunctionResolver getXPathFunctionResolver ()
Return the current function resolver.
null is returned in no function resolver is in effect.
| Returns | |
|---|---|
XPathFunctionResolver |
Current function resolver. |
XPathVariableResolver getXPathVariableResolver ()
Return the current variable resolver.
null is returned in no variable resolver is in effect.
| Returns | |
|---|---|
XPathVariableResolver |
Current variable resolver. |
void reset ()
Reset this XPath to its original configuration.
XPath is reset to the same state as when it was created with
newXPath().
reset() is designed to allow the reuse of existing XPaths
thus saving resources associated with the creation of new XPaths.
The reset XPath is not guaranteed to have the same XPathFunctionResolver, XPathVariableResolver
or NamespaceContext Objects, e.g. equals(Object).
It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver
and NamespaceContext.
void setNamespaceContext (NamespaceContext nsContext)
Establish a namespace context.
A NullPointerException is thrown if nsContext is null.
| Parameters | |
|---|---|
nsContext |
NamespaceContext:
Namespace context to use. |
| Throws | |
|---|---|
NullPointerException |
If nsContext is null.
|
void setXPathFunctionResolver (XPathFunctionResolver resolver)
Establish a function resolver.
A NullPointerException is thrown if resolver is null.
| Parameters | |
|---|---|
resolver |
XPathFunctionResolver:
XPath function resolver. |
| Throws | |
|---|---|
NullPointerException |
If resolver is null.
|
void setXPathVariableResolver (XPathVariableResolver resolver)
Establish a variable resolver.
A NullPointerException is thrown if resolver is null.
| Parameters | |
|---|---|
resolver |
XPathVariableResolver:
Variable resolver. |
| Throws | |
|---|---|
NullPointerException |
If resolver is null.
|
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