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. * | *
An XPath expression is not thread-safe and not reentrant.
* In other words, it is the application's responsibility to make
* sure that one {@link XPathExpression} object is not used from
* more than one thread at any given time, and while the evaluate
* method is invoked, applications may not recursively call
* the evaluate method.
*
* * @author Norman Walsh * @author Jeff Suttor * @see XML Path Language (XPath) Version 1.0, Expressions * @since 1.5 */ public interface XPathExpression { /** *
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.
Object that is the result of evaluating the expression and converting the result to
* returnType.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If returnType is not one of the types defined in {@link XPathConstants}.
* @throws NullPointerException If returnType is null.
*/
public Object evaluate(Object item, QName returnType)
throws XPathExpressionException;
/**
* 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.
*
* @param item The starting context (a node, for example).
*
* @return 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.
*/
public String evaluate(Object item)
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 {@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.
InputSource of the document to evaluate over.
* @param returnType The desired return type.
*
* @return The Object that is the result of evaluating the expression and converting the result to
* returnType.
*
* @throws XPathExpressionException If the expression cannot be evaluated.
* @throws IllegalArgumentException If returnType is not one of the types defined in {@link XPathConstants}.
* @throws NullPointerException If source or returnType 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 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.
InputSource of the document to evaluate over.
*
* @return 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.
* @throws NullPointerException If source is null.
*/
public String evaluate(InputSource source)
throws XPathExpressionException;
}