Module java.xml

Package javax.xml.xpath

Interface XPath

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.

Evaluation of XPath Expressions

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:

XML Path Language (XPath) Version 1.0

Method Summary

Modifier and Type	Method	Description
XPathExpression	compile(String expression)	Compile an XPath expression for later evaluation.
String	evaluate(String expression, Object item)	Evaluate an XPath expression in the specified context and return the result as a String.
Object	evaluate(String expression, Object item, QName returnType)	Evaluate an XPath expression in the specified context and return the result as the specified type.
String	evaluate(String expression, InputSource source)	Evaluate an XPath expression in the context of the specified InputSource and return the result as a String.
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.
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 the class 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 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(NamespaceContext nsContext)	Establish a namespace context.
void	setXPathFunctionResolver(XPathFunctionResolver resolver)	Establish a function resolver.
void	setXPathVariableResolver(XPathVariableResolver resolver)	Establish a variable resolver.

Method Details

reset

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 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. Object.equals(Object obj). It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver and NamespaceContext.

setXPathVariableResolver

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.

getXPathVariableResolver

XPathVariableResolver getXPathVariableResolver()

Return the current variable resolver.

null is returned in no variable resolver is in effect.

Returns:

Current variable resolver.

setXPathFunctionResolver

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.

getXPathFunctionResolver

XPathFunctionResolver getXPathFunctionResolver()

Return the current function resolver.

null is returned in no function resolver is in effect.

Returns:

Current function resolver.

setNamespaceContext

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.

getNamespaceContext

NamespaceContext getNamespaceContext()

Return the current namespace context.

null is returned in no namespace context is in effect.

Returns:

Current Namespace context.

compile

XPathExpression compile(String expression)
                 throws XPathExpressionException

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 resovled with the XPathFunctionResolver.

If expression contains any variables, the XPathVariableResolver in effect at compile time will be used to resolve them.

Parameters:

expression - The XPath expression.

Returns:

Compiled XPath expression.

Throws:

XPathExpressionException - If expression cannot be compiled.

NullPointerException - If expression is null.

evaluate

Object evaluate(String expression,
 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.

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.

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 of returnType.

Throws:

XPathExpressionException - If expression cannot be evaluated.

IllegalArgumentException - If returnType is not one of the types defined in