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Added in API level 8

XPath

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:

Summary

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 XPath expression in the specified context and return the result as the specified type.

abstract String evaluate(String expression, Object item)

Evaluate an XPath expression in the specified context and return the result as a String.

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.

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.

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 XPath to its original configuration.

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.

Public methods

compile

Added in API level 8
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.

evaluate

Added in API level 8
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.

evaluate

Added in API level 8
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.

evaluate

Added in API level 8
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.

evaluate

Added in API level 8
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.

getNamespaceContext

Added in API level 8
NamespaceContext getNamespaceContext ()

Return the current namespace context.

null is returned in no namespace context is in effect.

Returns
NamespaceContext Current Namespace context.

getXPathFunctionResolver

Added in API level 8
XPathFunctionResolver getXPathFunctionResolver ()

Return the current function resolver.

null is returned in no function resolver is in effect.

Returns
XPathFunctionResolver Current function resolver.

getXPathVariableResolver

Added in API level 8
XPathVariableResolver getXPathVariableResolver ()

Return the current variable resolver.

null is returned in no variable resolver is in effect.

Returns
XPathVariableResolver Current variable resolver.

reset

Added in API level 8
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.

setNamespaceContext

Added in API level 8
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.

setXPathFunctionResolver

Added in API level 8
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.

setXPathVariableResolver

Added in API level 8
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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