public interface XPath
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.
Modifier and Type | Method | Description |
---|---|---|
XPathExpression |
compile |
Compile an XPath expression for later evaluation. |
String |
evaluate |
Evaluate an XPath expression in the specified context and return the result as a String . |
Object |
evaluate |
Evaluate an XPath expression in the specified context and return the result as the specified type. |
String |
evaluate |
Evaluate an XPath expression in the context of the specified InputSource and return the result as a String . |
Object |
evaluate |
Evaluate an XPath expression in the context of the specified InputSource and return the result as the specified type. |
default XPathEvaluationResult |
evaluateExpression |
Evaluate an XPath expression in the specified context. |
default <T> T |
evaluateExpression |
Evaluate an XPath expression in the specified context and return the result with the type specified through the class type
|
default XPathEvaluationResult |
evaluateExpression |
Evaluate an XPath expression in the specified context. |
default <T> T |
evaluateExpression |
Evaluate an XPath expression in the context of the specified source and return the result as specified. |
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 |
Establish a namespace context. |
void |
setXPathFunctionResolver |
Establish a function resolver. |
void |
setXPathVariableResolver |
Establish a variable resolver. |
void reset()
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)
A NullPointerException
is thrown if resolver
is null
.
resolver
- Variable resolver.NullPointerException
- If resolver
is null
.XPathVariableResolver getXPathVariableResolver()
null
is returned in no variable resolver is in effect.
void setXPathFunctionResolver(XPathFunctionResolver resolver)
A NullPointerException
is thrown if resolver
is null
.
resolver
- XPath function resolver.NullPointerException
- If resolver
is null
.XPathFunctionResolver getXPathFunctionResolver()
null
is returned in no function resolver is in effect.
void setNamespaceContext(NamespaceContext nsContext)
A NullPointerException
is thrown if nsContext
is null
.
nsContext
- Namespace context to use.NullPointerException
- If nsContext
is null
.NamespaceContext getNamespaceContext()
null
is returned in no namespace context is in effect.
XPathExpression compile(String expression) throws XPathExpressionException
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
contains any variables, the XPathVariableResolver
in effect at compile time will be used to resolve them.
expression
- The XPath expression.XPathExpressionException
- If expression
cannot be compiled.NullPointerException
- If expression
is null
.Object evaluate(String expression, Object item, QName returnType) throws XPathExpressionException
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.
The parameter item
represents the context the XPath expression will be operated on. 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.
Node
.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.Object
of returnType
.XPathExpressionException
- If expression
cannot be evaluated.IllegalArgumentException
- If returnType
is not one of the types defined in XPathConstants
( NUMBER
, STRING
, BOOLEAN
, NODE
or NODESET
).NullPointerException
- If expression or returnType
is null
.String evaluate(String expression, Object item) throws XPathExpressionException
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.
The parameter item
represents the context the XPath expression will be operated on. 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.
Node
.expression
- The XPath expression.item
- The context the XPath expression will be evaluated in.String
.XPathExpressionException
- If expression
cannot be evaluated.NullPointerException
- If expression
is null
.Object evaluate(String expression, InputSource source, QName returnType) throws XPathExpressionException
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.
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.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) throws XPathExpressionException
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.
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.NullPointerException
- If expression or source
is null
.default <T> T evaluateExpression(String expression, Object item, Class<T> type) throws XPathExpressionException
class 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 is null
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.
(T)evaluate(expression, item,
XPathEvaluationResult.XPathResultType.getQNameType(type));
Since the evaluate
method does not support the ANY
type, specifying XPathEvaluationResult as the type will result in IllegalArgumentException. Any implementation supporting the ANY
type must override this method.Node
.T
- The class type that will be returned by the XPath expression.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.XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If type
is not of the types corresponding to the types defined in the XPathEvaluationResult.XPathResultType
, or XPathEvaluationResult is specified as the type but an implementation supporting the ANY
type is not available.NullPointerException
- If expression or type
is null
.default XPathEvaluationResult<?> evaluateExpression(String expression, Object item) throws XPathExpressionException
evaluateExpression(String expression, Object item, Class type)
with type XPathEvaluationResult
:
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 is null
, the operation must have no dependency on the context, otherwise an XPathExpressionException will be thrown.
evaluateExpression(expression, item, XPathEvaluationResult.class);
Since the evaluate
method does not support the ANY
type, the default implementation of this method will always throw an IllegalArgumentException. Any implementation supporting the ANY
type must therefore override this method.Node
.expression
- The XPath expression.item
- The context the XPath expression will be evaluated in.XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If the implementation of this method does not support the ANY
type.NullPointerException
- If expression
is null
.default <T> T evaluateExpression(String expression, InputSource source, Class<T> type) throws XPathExpressionException
source
and return the result as specified. This method builds a data model for the InputSource
and calls evaluateExpression(String expression, Object item, Class type)
on the resulting document object. The data model is usually Document
(T)evaluate(expression, source,
XPathEvaluationResult.XPathResultType.getQNameType(type));
Since the evaluate
method does not support the ANY
type, specifying XPathEvaluationResult as the type will result in IllegalArgumentException. Any implementation supporting the ANY
type must override this method.T
- The class type that will be returned by the XPath expression.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.XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If type
is not of the types corresponding to the types defined in the XPathResultType
, or XPathEvaluationResult is specified as the type but an implementation supporting the ANY
type is not available.NullPointerException
- If expression, source or type
is null
.default XPathEvaluationResult<?> evaluateExpression(String expression, InputSource source) throws XPathExpressionException
evaluateExpression(String expression, Object item, Class type)
with type XPathEvaluationResult
:
evaluateExpression(expression, item, XPathEvaluationResult.class);
evaluateExpression(expression, source, XPathEvaluationResult.class);
Since the evaluate
method does not support the ANY
type, the default implementation of this method will always throw an IllegalArgumentException. Any implementation supporting the ANY
type must therefore override this method.expression
- The XPath expression.source
- The input source of the document to evaluate over.XPathExpressionException
- If the expression cannot be evaluated.IllegalArgumentException
- If the implementation of this method does not support the ANY
type.NullPointerException
- If expression or source
is null
.
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