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XPath.javaAPI DocJava SE 6 API14063Tue Jun 10 00:27:16 BST 2008javax.xml.xpath

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 {@link XPathVariableResolver} set with {@link #setXPathVariableResolver(XPathVariableResolver resolver)}. 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} set with {@link #setXPathFunctionResolver(XPathFunctionResolver resolver)}. 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 set with {@link #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 {@link XPathConstants}. Conversion to the return type follows XPath conversion rules.

An XPath object is not thread-safe and not reentrant. In other words, it is the application's responsibility to make sure that one {@link XPath} 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
version
$Revision: 1.5 $, $Date: 2005/10/13 17:00:49 $
see
XML Path Language (XPath) Version 1.0
since
1.5

Fields Summary
Constructors Summary
Methods Summary
public javax.xml.xpath.XPathExpressioncompile(java.lang.String expression)

Compile an XPath expression for later evaluation.

If expression contains any {@link XPathFunction}s, they must be available via the {@link XPathFunctionResolver}. An {@link XPathExpressionException} will be thrown if the XPathFunction cannot be resovled with the XPathFunctionResolver.

If expression contains any variables, the {@link XPathVariableResolver} in effect at compile time will be used to resolve them.

If expression is null, a NullPointerException is thrown.

param
expression The XPath expression.
return
Compiled XPath expression.
throws
XPathExpressionException If expression cannot be compiled.
throws
NullPointerException If expression is null.

public java.lang.Stringevaluate(java.lang.String expression, java.lang.Object item)

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

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

param
expression The XPath expression.
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 expression cannot be evaluated.
throws
NullPointerException If expression is null.

public java.lang.Objectevaluate(java.lang.String expression, org.xml.sax.InputSource source, javax.xml.namespace.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 {@link InputSource} and calls {@link #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 {@link XPathConstants}, then an IllegalArgumentException is thrown.

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

param
expression The XPath expression.
param
source The input source of the document to evaluate over.
param
returnType The desired return type.
return
The Object that encapsulates the result of evaluating the expression.
throws
XPathExpressionException If expression cannot be evaluated.
throws
IllegalArgumentException If returnType is not one of the types defined in {@link XPathConstants}.
throws
NullPointerException If expression, source or returnType is null.

public java.lang.Stringevaluate(java.lang.String expression, org.xml.sax.InputSource source)

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

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

param
expression The XPath expression.
param
source The 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 expression cannot be evaluated.
throws
NullPointerException If expression or source is null.

public java.lang.Objectevaluate(java.lang.String expression, java.lang.Object item, javax.xml.namespace.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 {@link XPathConstants} ( {@link XPathConstants#NUMBER NUMBER}, {@link XPathConstants#STRING STRING}, {@link XPathConstants#BOOLEAN BOOLEAN}, {@link XPathConstants#NODE NODE} or {@link XPathConstants#NODESET 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.

param
expression The XPath expression.
param
item The starting context (a node, for example).
param
returnType The desired return type.
return
Result of evaluating an XPath expression as an Object of returnType.
throws
XPathExpressionException If expression cannot be evaluated.
throws
IllegalArgumentException If returnType is not one of the types defined in {@link XPathConstants}.
throws
NullPointerException If expression or returnType is null.

public javax.xml.namespace.NamespaceContextgetNamespaceContext()

Return the current namespace context.

null is returned in no namespace context is in effect.

return
Current Namespace context.

public javax.xml.xpath.XPathFunctionResolvergetXPathFunctionResolver()

Return the current function resolver.

null is returned in no function resolver is in effect.

return
Current function resolver.

public javax.xml.xpath.XPathVariableResolvergetXPathVariableResolver()

Return the current variable resolver.

null is returned in no variable resolver is in effect.

return
Current variable resolver.

public voidreset()

Reset this XPath to its original configuration.

XPath is reset to the same state as when it was created with {@link 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 {@link XPathFunctionResolver}, {@link XPathVariableResolver} or {@link NamespaceContext} Objects, e.g. {@link Object#equals(Object obj)}. It is guaranteed to have a functionally equal XPathFunctionResolver, XPathVariableResolver and NamespaceContext.

public voidsetNamespaceContext(javax.xml.namespace.NamespaceContext nsContext)

Establish a namespace context.

A NullPointerException is thrown if nsContext is null.

param
nsContext Namespace context to use.
throws
NullPointerException If nsContext is null.

public voidsetXPathFunctionResolver(javax.xml.xpath.XPathFunctionResolver resolver)

Establish a function resolver.

A NullPointerException is thrown if resolver is null.

param
resolver XPath function resolver.
throws
NullPointerException If resolver is null.

public voidsetXPathVariableResolver(javax.xml.xpath.XPathVariableResolver resolver)

Establish a variable resolver.

A NullPointerException is thrown if resolver is null.

param
resolver Variable resolver.
throws
NullPointerException If resolver is null.