XPathExpression 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`. 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`. 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.
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 String evaluate (InputSource source) throws XPathExpressionException

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

This method calls XPathExpression.evaluate(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 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:
- source - The InputSource of the document to evaluate over.
Throws:
- XPathExpressionException - If the expression cannot be evaluated.
- NullPointerException - If source is null.

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

Evaluate the compiled 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 XPathExpression.evaluate(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 source or returnType is null, then a NullPointerException is thrown.

Returns: The Object that is the result of evaluating the expression and converting the result to returnType.
Parameters:
- source - The InputSource of the document to evaluate over.
- returnType - The desired return type.
Throws:
- XPathExpressionException - If the expression cannot be evaluated.
- IllegalArgumentException - If returnType is not one of the types defined in {@link XPathConstants}.
- NullPointerException - If source or returnType is null.

public String evaluate (Object item) throws XPathExpressionException

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

public Object evaluate (Object item, QName returnType) throws XPathExpressionException

Evaluate the compiled 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, then an IllegalArgumentException is thrown.

If a null value is provided for item, an empty document will be used for the context. If returnType is null, then a NullPointerException is thrown.

Returns: The Object that is the result of evaluating the expression and converting the result to returnType.
Parameters:
- item - The starting context (a node, for example).
- returnType - The desired return type.
Throws:
- XPathExpressionException - If the expression cannot be evaluated.
- IllegalArgumentException - If returnType is not one of the types defined in {@link XPathConstants}.
- NullPointerException - If returnType is null.