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javax.xml.xpath

Interface 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 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 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 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.
Version:
$Revision: 226183 $, $Date: 2005-04-08 12:39:14 +0200 (Fri, 08 Apr 2005) $
Authors:
Norman Walsh
Jeff Suttor
Since:
1.5
See Also:
XML Path Language (XPath) Version 1.0

Method Summary

XPathExpression
compile(String expression)
Compile an XPath expression for later evaluation.
String
evaluate(String expression, Object item)
Evaluate an XPath expression in the specified context and return the result as a String.
Object
evaluate(String expression, Object item, QName returnType)
Evaluate an XPath expression in the specified context and return the result as the specified type.
String
evaluate(String expression, InputSource source)
Evaluate an XPath expression in the context of the specified InputSource and return the result as a String.
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.
NamespaceContext
getNamespaceContext()
Return the current namespace context.
XPathFunctionResolver
getXPathFunctionResolver()
Return the current function resolver.
XPathVariableResolver
getXPathVariableResolver()
Return the current variable resolver.
void
reset()
Reset this XPath to its original configuration.
void
setNamespaceContext(NamespaceContext nsContext)
Establish a namespace context.
void
setXPathFunctionResolver(XPathFunctionResolver resolver)
Establish a function resolver.
void
setXPathVariableResolver(XPathVariableResolver resolver)
Establish a variable resolver.

Method Details

compile

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 is null, a NullPointerException is thrown.

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

evaluate

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 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.

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.

evaluate

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.

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.

evaluate

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 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.

Parameters:
expression - The XPath expression.
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 expression cannot be evaluated.

evaluate

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 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.

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.

getNamespaceContext

public NamespaceContext getNamespaceContext()
Return the current namespace context.

null is returned in no namespace context is in effect.

Returns:
Current Namespace context.

getXPathFunctionResolver

public XPathFunctionResolver getXPathFunctionResolver()
Return the current function resolver.

null is returned in no function resolver is in effect.

Returns:
Current function resolver.

getXPathVariableResolver

public XPathVariableResolver getXPathVariableResolver()
Return the current variable resolver.

null is returned in no variable resolver is in effect.

Returns:
Current variable resolver.

reset

public void reset()
Reset this XPath to its original configuration.

XPath is reset to the same state as when it was created with XPathFactory.newXPath(). reset() is designed to allow the reuse of existing XPaths thus saving resources associated with the creation of new XPaths.

The reset XPath is not guaranteed to have the same XPathFunctionResolver, XPathVariableResolver or NamespaceContext Objects, e.g. Object.equals(Object obj). It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver and NamespaceContext.

setNamespaceContext

public void setNamespaceContext(NamespaceContext nsContext)
Establish a namespace context.

A NullPointerException is thrown if nsContext is null.

Parameters:
nsContext - Namespace context to use.

setXPathFunctionResolver

public void setXPathFunctionResolver(XPathFunctionResolver resolver)
Establish a function resolver.

A NullPointerException is thrown if resolver is null.

Parameters:
resolver - XPath function resolver.

setXPathVariableResolver

public void setXPathVariableResolver(XPathVariableResolver resolver)
Establish a variable resolver.

A NullPointerException is thrown if resolver is null.

Parameters:
resolver - Variable resolver.

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