org.apache.xpath.jaxp

Class XPathImpl

public class XPathImpl extends Object implements XPath

The XPathImpl class provides implementation for the methods defined in javax.xml.xpath.XPath interface. This provide simple access to the results of an XPath expression.

Version: $Revision$

Author: Ramesh Mandava

Method Summary
XPathExpression	compile(String expression) Compile an XPath expression for later evaluation. If `expression` contains any XPathFunctions, they must be available via the XPathFunctionResolver.
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" section of JAXP 1.3 spec for context item evaluation, variable, function and `QName` resolution and return type conversion. If `returnType` is not one of the types defined in XPathConstants ( `XPathConstants#NUMBER NUMBER`, `XPathConstants#STRING STRING`, `XPathConstants#BOOLEAN BOOLEAN`, `XPathConstants#NODE NODE` or `XPathConstants#NODESET NODESET`) then an `IllegalArgumentException` is thrown. If a `null` value is provided for `item`, an empty document will be used for the context.
String	evaluate(String expression, Object item) Evaluate an XPath expression in the specified context and return the result as a `String`. This method calls XPathImpl with a `returnType` of XPathConstants#STRING. See "Evaluation of XPath Expressions" of JAXP 1.3 spec 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.
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 XPathImpl on the resulting document object. See "Evaluation of XPath Expressions" section of JAXP 1.3 spec 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.
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 XPathImpl with a `returnType` of XPathConstants#STRING. See "Evaluation of XPath Expressions" section of JAXP 1.3 spec for context item evaluation, variable, function and QName resolution and return type conversion. If `expression` or `source` is `null`, then a `NullPointerException` is thrown.
NamespaceContext	getNamespaceContext() Returns the current namespace context.
XPathFunctionResolver	getXPathFunctionResolver() Returns the current function resolver.
XPathVariableResolver	getXPathVariableResolver() Returns the 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 XPathFactory.
void	setNamespaceContext(NamespaceContext nsContext) Establishes a namespace context.
void	setXPathFunctionResolver(XPathFunctionResolver resolver) Establishes a function resolver.
void	setXPathVariableResolver(XPathVariableResolver resolver) Establishes a variable resolver.

Method Detail

compile

public 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 resovled with the XPathFunctionResolver.

If expression is null, a NullPointerException is thrown.

Parameters: expression The XPath expression.

Returns: Compiled XPath expression.

Throws: XPathExpressionException If expression cannot be compiled. NullPointerException If expression is null.

evaluate

public 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" section of JAXP 1.3 spec for context item evaluation, variable, function and QName resolution and return type conversion.

If returnType is not one of the types defined in XPathConstants ( XPathConstants#NUMBER NUMBER, XPathConstants#STRING STRING, XPathConstants#BOOLEAN BOOLEAN, XPathConstants#NODE NODE or XPathConstants#NODESET 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 The XPath expression. item The starting context (node or node list, for example). returnType The desired return type.

Returns: 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

public String evaluate(String expression, Object item)

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

This method calls XPathImpl with a returnType of XPathConstants#STRING.

See "Evaluation of XPath Expressions" of JAXP 1.3 spec 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 The XPath expression. item The starting context (node or node list, for example).

Returns: 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

public 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 XPathImpl on the resulting document object.

See "Evaluation of XPath Expressions" section of JAXP 1.3 spec 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 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 If returnType is not one of the types defined in XPathConstants. NullPointerException If expression, source or returnType is null.

evaluate

public 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 XPathImpl with a returnType of XPathConstants#STRING.

See "Evaluation of XPath Expressions" section of JAXP 1.3 spec 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 The XPath expression. source The InputSource of the document to evaluate over.

Returns: 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

public NamespaceContext getNamespaceContext()

Returns the current namespace context.

Returns: Current Namespace context

getXPathFunctionResolver

public XPathFunctionResolver getXPathFunctionResolver()

Returns the current function resolver.

Returns: Current function resolver

getXPathVariableResolver

public XPathVariableResolver getXPathVariableResolver()

Returns the current variable resolver.

Returns: Current variable resolver

reset

public void reset()

Reset this XPath to its original configuration.

XPath is reset to the same state as when it was created with XPathFactory. 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.

setNamespaceContext

public void setNamespaceContext(NamespaceContext nsContext)

Establishes a namespace context.

Parameters: nsContext Namespace context to use

setXPathFunctionResolver

public void setXPathFunctionResolver(XPathFunctionResolver resolver)

Establishes a function resolver.

Parameters: resolver XPath function resolver

setXPathVariableResolver

public void setXPathVariableResolver(XPathVariableResolver resolver)

Establishes a variable resolver.

Parameters: resolver Variable Resolver