javax.xml.xpath

Interface XPathExpression

public interface XPathExpression

XPathExpression provides access to compiled XPath 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}. 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}. 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.
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, Expressions

Method Summary
Objectevaluate(Object item, QName returnType)

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 {@link XPathConstants}, then an IllegalArgumentException is thrown.

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

Stringevaluate(Object item)

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

This method calls {@link #evaluate(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(InputSource source, QName returnType)

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 {@link InputSource} and calls {@link #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 {@link XPathConstants}, then an IllegalArgumentException is thrown.

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

Stringevaluate(InputSource source)

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

This method calls {@link #evaluate(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 source is null, then a NullPointerException is thrown.

Method Detail

evaluate

public Object evaluate(Object item, QName returnType)

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 {@link 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.

Parameters: item The starting context (node or node list, for example). returnType The desired return type.

Returns: The Object that is the result of evaluating the expression and converting the result to returnType.

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.

evaluate

public String evaluate(Object item)

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

This method calls {@link #evaluate(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.

Parameters: 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 the expression cannot be evaluated.

evaluate

public Object evaluate(InputSource source, QName returnType)

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 {@link InputSource} and calls {@link #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 {@link XPathConstants}, then an IllegalArgumentException is thrown.

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

Parameters: source The InputSource of the document to evaluate over. returnType The desired return type.

Returns: The Object that is the result of evaluating the expression and converting the result to returnType.

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.

evaluate

public String evaluate(InputSource source)

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

This method calls {@link #evaluate(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 source is null, then a NullPointerException is thrown.

Parameters: 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 the expression cannot be evaluated. NullPointerException If source is null.