XPath
provides access to the XPath evaluation environment and expressions.
The XPath evaluation is affected by the factors described in the following table.
Factor | Behavior |
---|---|
context | The type of the context is implementation-dependent. If the value is null, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown. 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.
|
An XPath object is not thread-safe and not reentrant.
In other words, it is the application's responsibility to make
sure that one XPath
object is not used from
more than one thread at any given time, and while the evaluate
method is invoked, applications may not recursively call
the evaluate
method.
- Since:
- 1.5
- See Also:
-
Method Summary
Modifier and TypeMethodDescriptionCompile an XPath expression for later evaluation.Evaluate an XPath expression in the specified context and return the result as aString
.Evaluate anXPath
expression in the specified context and return the result as the specified type.evaluate
(String expression, InputSource source) Evaluate an XPath expression in the context of the specifiedInputSource
and return the result as aString
.evaluate
(String expression, InputSource source, QName returnType) Evaluate an XPath expression in the context of the specifiedInputSource
and return the result as the specified type.default XPathEvaluationResult
<?> evaluateExpression
(String expression, Object item) Evaluate an XPath expression in the specified context.default <T> T
evaluateExpression
(String expression, Object item, Class<T> type) Evaluate an XPath expression in the specified context and return the result with the type specified through theclass type
default XPathEvaluationResult
<?> evaluateExpression
(String expression, InputSource source) Evaluate an XPath expression in the specified context.default <T> T
evaluateExpression
(String expression, InputSource source, Class<T> type) Evaluate an XPath expression in the context of the specifiedsource
and return the result as specified.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 thisXPath
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:
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:
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:
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 resovled with theXPathFunctionResolver
.If
expression
contains any variables, theXPathVariableResolver
in effect at compile time will be used to resolve them.- Parameters:
expression
- The XPath expression.- Returns:
- Compiled XPath expression.
- Throws:
XPathExpressionException
- Ifexpression
cannot be compiled.NullPointerException
- Ifexpression
isnull
.
-
evaluate
Evaluate anXPath
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.The parameter
item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value isnull
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.- Implementation Note:
- The type of the context is usually
Node
. - Parameters:
expression
- The XPath expression.item
- The context the XPath expression will be evaluated in.returnType
- The result type expected to be returned by the XPath expression.- Returns:
- The result of evaluating an XPath expression as an
Object
ofreturnType
. - Throws:
XPathExpressionException
- Ifexpression
cannot be evaluated.IllegalArgumentException
- IfreturnType
is not one of the types defined inXPathConstants
(NUMBER
,STRING
,BOOLEAN
,NODE
orNODESET
).NullPointerException
- Ifexpression or returnType
isnull
.
-
evaluate
Evaluate an XPath expression in the specified context and return the result as aString
.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.
The parameter
item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value isnull
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.- Implementation Note:
- The type of the context is usually
Node
. - Parameters:
expression
- The XPath expression.item
- The context the XPath expression will be evaluated in.- Returns:
- The result of evaluating an XPath expression as a
String
. - Throws:
XPathExpressionException
- Ifexpression
cannot be evaluated.NullPointerException
- Ifexpression
isnull
.
-
evaluate
Object evaluate(String expression, InputSource source, QName returnType) throws XPathExpressionException Evaluate an XPath expression in the context of the specifiedInputSource
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.
- 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
- IfreturnType
is not one of the types defined inXPathConstants
.NullPointerException
- Ifexpression, source or returnType
isnull
.
-
evaluate
Evaluate an XPath expression in the context of the specifiedInputSource
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.
- 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.NullPointerException
- Ifexpression or source
isnull
.
-
evaluateExpression
default <T> T evaluateExpression(String expression, Object item, Class<T> type) throws XPathExpressionException Evaluate an XPath expression in the specified context and return the result with the type specified through theclass type
The parameter
item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value isnull
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.- Implementation Requirements:
- The default implementation in the XPath API is equivalent to:
(T)evaluate(expression, item, XPathEvaluationResult.XPathResultType.getQNameType(type));
evaluate
method does not support theANY
type, specifying XPathEvaluationResult as the type will result in IllegalArgumentException. Any implementation supporting theANY
type must override this method. - Implementation Note:
- The type of the context is usually
Node
. - Type Parameters:
T
- The class type that will be returned by the XPath expression.- Parameters:
expression
- The XPath expression.item
- The context the XPath expression will be evaluated in.type
- The class type expected to be returned by the XPath expression, must be one of the types described in section 3.2 Class types in the package summary.- Returns:
- The result of evaluating the expression.
- Throws:
XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- Iftype
is not of the types corresponding to the types defined in theXPathEvaluationResult.XPathResultType
, or XPathEvaluationResult is specified as the type but an implementation supporting theANY
type is not available.NullPointerException
- Ifexpression or type
isnull
.- Since:
- 9
-
evaluateExpression
default XPathEvaluationResult<?> evaluateExpression(String expression, Object item) throws XPathExpressionException Evaluate an XPath expression in the specified context. This is equivalent to callingevaluateExpression(String expression, Object item, Class type)
with typeXPathEvaluationResult
:evaluateExpression(expression, item, XPathEvaluationResult.class);
The parameter
item
represents the context the XPath expression will be operated on. The type of the context is implementation-dependent. If the value isnull
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.- Implementation Requirements:
- The default implementation in the XPath API is equivalent to:
evaluateExpression(expression, item, XPathEvaluationResult.class);
evaluate
method does not support theANY
type, the default implementation of this method will always throw an IllegalArgumentException. Any implementation supporting theANY
type must therefore override this method. - Implementation Note:
- The type of the context is usually
Node
. - Parameters:
expression
- The XPath expression.item
- The context the XPath expression will be evaluated in.- Returns:
- The result of evaluating the expression.
- Throws:
XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If the implementation of this method does not support theANY
type.NullPointerException
- Ifexpression
isnull
.- Since:
- 9
-
evaluateExpression
default <T> T evaluateExpression(String expression, InputSource source, Class<T> type) throws XPathExpressionException Evaluate an XPath expression in the context of the specifiedsource
and return the result as specified.This method builds a data model for the
InputSource
and callsevaluateExpression(String expression, Object item, Class type)
on the resulting document object. The data model is usuallyDocument
- Implementation Requirements:
- The default implementation in the XPath API is equivalent to:
(T)evaluate(expression, source, XPathEvaluationResult.XPathResultType.getQNameType(type));
evaluate
method does not support theANY
type, specifying XPathEvaluationResult as the type will result in IllegalArgumentException. Any implementation supporting theANY
type must override this method. - Type Parameters:
T
- The class type that will be returned by the XPath expression.- Parameters:
expression
- The XPath expression.source
- The input source of the document to evaluate over.type
- The class type expected to be returned by the XPath expression, must be one of the types described in section 3.2 Class types in the package summary.- Returns:
- The result of evaluating the expression.
- Throws:
XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- Iftype
is not of the types corresponding to the types defined in theXPathResultType
, or XPathEvaluationResult is specified as the type but an implementation supporting theANY
type is not available.NullPointerException
- Ifexpression, source or type
isnull
.- Since:
- 9
-
evaluateExpression
default XPathEvaluationResult<?> evaluateExpression(String expression, InputSource source) throws XPathExpressionException Evaluate an XPath expression in the specified context. This is equivalent to callingevaluateExpression(String expression, Object item, Class type)
with typeXPathEvaluationResult
:evaluateExpression(expression, item, XPathEvaluationResult.class);
- Implementation Requirements:
- The default implementation in the XPath API is equivalent to:
evaluateExpression(expression, source, XPathEvaluationResult.class);
evaluate
method does not support theANY
type, the default implementation of this method will always throw an IllegalArgumentException. Any implementation supporting theANY
type must therefore override this method. - Parameters:
expression
- The XPath expression.source
- The input source of the document to evaluate over.- Returns:
- The result of evaluating the expression.
- Throws:
XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If the implementation of this method does not support theANY
type.NullPointerException
- Ifexpression or source
isnull
.- Since:
- 9
-