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 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.

Public Method Summary

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

public abstract 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 The XPath expression.
Returns
  • Compiled XPath expression.
Throws
XPathExpressionException If expression cannot be compiled.
NullPointerException If expression is null.

public 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.

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 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.

public abstract 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 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.

public 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.

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 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.

public 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.

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 The XPath expression.
source The InputSource of the document to evaluate over.