javax.xml.xpath

Interface XPath

public interface 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 {@link XPathVariableResolver} set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}. An {@link 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 {@link XPathFunctionResolver} set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}. An {@link 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 {@link #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 {@link XPathConstants}. Conversion to the return type follows XPath conversion rules.

Since: 1.5

Version: $Revision: 226183 $, $Date: 2005-04-08 06:39:14 -0400 (Fri, 08 Apr 2005) $

Author: Norman Walsh Jeff Suttor

See Also: XML Path Language (XPath) Version 1.0

Method Summary
XPathExpressioncompile(String expression)

Compile an XPath expression for later evaluation.

If expression contains any {@link XPathFunction}s, they must be available via the {@link XPathFunctionResolver}.

Objectevaluate(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 {@link XPathConstants} ( {@link XPathConstants#NUMBER NUMBER}, {@link XPathConstants#STRING STRING}, {@link XPathConstants#BOOLEAN BOOLEAN}, {@link XPathConstants#NODE NODE} or {@link 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.

Stringevaluate(String expression, Object item)

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

This method calls {@link #evaluate(String expression, Object item, QName returnType)} with a returnType of {@link XPathConstants#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.

Objectevaluate(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 {@link InputSource} and calls {@link #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.

If returnType is not one of the types defined in {@link XPathConstants}, then an IllegalArgumentException is thrown.

If expression, source or returnType is null, then a NullPointerException is thrown.

Stringevaluate(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 {@link #evaluate(String expression, InputSource source, QName returnType)} with a returnType of {@link XPathConstants#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.

NamespaceContextgetNamespaceContext()

Return the current namespace context.

null is returned in no namespace context is in effect.

XPathFunctionResolvergetXPathFunctionResolver()

Return the current function resolver.

null is returned in no function resolver is in effect.

XPathVariableResolvergetXPathVariableResolver()

Return the current variable resolver.

null is returned in no variable resolver is in effect.

voidreset()

Reset this XPath to its original configuration.

XPath is reset to the same state as when it was created with {@link XPathFactory#newXPath()}.

voidsetNamespaceContext(NamespaceContext nsContext)

Establish a namespace context.

A NullPointerException is thrown if nsContext is null.

voidsetXPathFunctionResolver(XPathFunctionResolver resolver)

Establish a function resolver.

A NullPointerException is thrown if resolver is null.

voidsetXPathVariableResolver(XPathVariableResolver resolver)

Establish a variable resolver.

A NullPointerException is thrown if resolver is null.

Method Detail

compile

public XPathExpression compile(String expression)

Compile an XPath expression for later evaluation.

If expression contains any {@link XPathFunction}s, they must be available via the {@link XPathFunctionResolver}. An {@link 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 for context item evaluation, variable, function and QName resolution and return type conversion.

If returnType is not one of the types defined in {@link XPathConstants} ( {@link XPathConstants#NUMBER NUMBER}, {@link XPathConstants#STRING STRING}, {@link XPathConstants#BOOLEAN BOOLEAN}, {@link XPathConstants#NODE NODE} or {@link 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 {@link 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 {@link #evaluate(String expression, Object item, QName returnType)} with a returnType of {@link XPathConstants#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 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 {@link InputSource} and calls {@link #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.

If returnType is not one of the types defined in {@link 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 {@link 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 {@link #evaluate(String expression, InputSource source, QName returnType)} with a returnType of {@link XPathConstants#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 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()

Return the current namespace context.

null is returned in no namespace context is in effect.

Returns: Current Namespace context.

getXPathFunctionResolver

public XPathFunctionResolver getXPathFunctionResolver()

Return the current function resolver.

null is returned in no function resolver is in effect.

Returns: Current function resolver.

getXPathVariableResolver

public XPathVariableResolver getXPathVariableResolver()

Return the current variable resolver.

null is returned in no variable resolver is in effect.

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 {@link 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 {@link XPathFunctionResolver}, {@link XPathVariableResolver} or {@link NamespaceContext} Objects, e.g. {@link Object#equals(Object obj)}. It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver and NamespaceContext.

setNamespaceContext

public 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.

setXPathFunctionResolver

public 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.

setXPathVariableResolver

public 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.