XPath JDK 1.6)

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 `XPath.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 `XPath.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 `XPath.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.

public 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.

If expression is null, a NullPointerException is thrown.

Returns: Compiled XPath expression.
Parameters:
- expression - The XPath expression.
Throws:
- XPathExpressionException - If expression cannot be compiled.
- NullPointerException - If expression is null.

public String evaluate (String expression, InputSource source) throws XPathExpressionException

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

This method calls XPath.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.

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

Returns: The String that is the result of evaluating the expression and converting the result to a String.
Parameters:
- expression - The XPath expression.
- source - The InputSource of the document to evaluate over.
Throws:
- XPathExpressionException - If expression cannot be evaluated.
- NullPointerException - If expression or source is null.

public Object evaluate (String expression, InputSource source, QName returnType) throws XPathExpressionException

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 XPath.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 XPathConstants, then an IllegalArgumentException is thrown.

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

Returns: The Object that encapsulates the result of evaluating the expression.
Parameters:
- expression - The XPath expression.
- source - The input source of the document to evaluate over.
- returnType - The desired return type.
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.

public String evaluate (String expression, Object item) throws XPathExpressionException

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

This method calls XPath.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.

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.

Returns: The String that is the result of evaluating the expression and converting the result to a String.
Parameters:
- expression - The XPath expression.
- item - The starting context (a node, for example).
Throws:
- XPathExpressionException - If expression cannot be evaluated.
- NullPointerException - If expression is null.

public 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.

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.

Returns: Result of evaluating an XPath expression as an Object of returnType.
Parameters:
- expression - The XPath expression.
- item - The starting context (a node, for example).
- returnType - The desired return type.
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.

public NamespaceContext getNamespaceContext ()

Return the current namespace context.

public XPathFunctionResolver getXPathFunctionResolver ()

Return the current function resolver.

public XPathVariableResolver getXPathVariableResolver ()

Return the current variable resolver.

public void reset ()

Reset this XPath to its original configuration.

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.

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.

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.