net.sf.saxon.sxpath

Class XPathEvaluator

java.lang.Object

net.sf.saxon.sxpath.XPathEvaluator

public class XPathEvaluator
extends Object

This class provides a native Saxon API for free-standing evaluation of XPath expressions. Unlike the JAXP API offered by XPathEvaluator it exposes Saxon classes and interfaces and thus provides a more strongly-typed interface with greater control over the detailed behaviour.

However, the preferred API for user applications calling XPath is the s9api XPathCompiler interface.

Since:

8.4

Author:

Michael H. Kay

Constructor Summary

Constructors

Constructor and Description
XPathEvaluator() Default constructor.
XPathEvaluator(Configuration config) Construct an XPathEvaluator with a specified configuration.

Method Summary

Methods

Modifier and Type	Method and Description
XPathExpression	createExpression(String expression) Prepare (compile) an XPath expression for subsequent evaluation.
XPathExpression	createPattern(String pattern) Prepare (compile) an XSLT pattern for subsequent evaluation.
XPathVariable	declareVariable(String uri, String localName) Declare a variable, making it available for use within a subsequently-compiled XPath expression.
Configuration	getConfiguration() Get the Configuration in use.
NamespaceResolver	getNamespaceResolver() Get the external namespace resolver, if one has been set using setNamespaceResolver(net.sf.saxon.om.NamespaceResolver)
XPathStaticContext	getStaticContext() Get the current static context.
void	setDefaultElementNamespace(String uri) Set the default namespace for elements and types
void	setNamespaceResolver(NamespaceResolver namespaceResolver) Set the external namespace resolver to be used.
void	setStaticContext(XPathStaticContext context) Set the static context for compiling XPath expressions.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

XPathEvaluator

public XPathEvaluator()

Default constructor. Creates an XPathEvaluator with a default configuration and name pool. Note that any source documents used by an XPath expression under this XPathEvaluator must be built using the Configuration that is implicitly created by this constructor, which is accessible using the getConfiguration() method.

XPathEvaluator

public XPathEvaluator(Configuration config)

Construct an XPathEvaluator with a specified configuration.

Parameters:

config - the configuration to be used. If the XPathEvaluator is to be used to run schema-aware XPath expressions this must be an instance of EnterpriseConfiguration

Method Detail

getConfiguration

public Configuration getConfiguration()

Get the Configuration in use.

Returns:

the Saxon configuration

declareVariable

public XPathVariable declareVariable(String uri,
                            String localName)

Declare a variable, making it available for use within a subsequently-compiled XPath expression. The variable may subsequently be assigned a value using the method XPathDynamicContext.setVariable(XPathVariable, net.sf.saxon.om.Sequence). Any external variable used in an XPath expression must be declared before the XPath expression is compiled.

Parameters:

uri - The namespace URI of the variable name. Use "" for the null namespace.

localName - The local part of the variable name.

Returns:

an object representing the variable

setStaticContext

public void setStaticContext(XPathStaticContext context)

Set the static context for compiling XPath expressions. This provides more detailed control over the environment in which the expression is compiled, for example it allows namespace prefixes to be declared, variables to be bound and functions to be defined. For most purposes, the static context can be defined by providing and tailoring an instance of the IndependentContext class. Until this method is called, a default static context is used, in which no namespaces are defined other than the standard ones (xml, xslt, and saxon), and no variables or functions (other than the core XPath functions) are available.

Parameters:

context - the XPath static context

Setting a new static context clears any variables and namespaces that have previously been declared.

getStaticContext

public XPathStaticContext getStaticContext()

Get the current static context. This will always return a value; if no static context has been supplied by the user, the system will have created its own. A system-created static context will always be an instance of IndependentContext

Returns:

the static context object

createExpression

public XPathExpression createExpression(String expression)
                                 throws XPathException

Prepare (compile) an XPath expression for subsequent evaluation.

Parameters:

expression - The XPath expression to be compiled, supplied as a string.

Returns:

an XPathExpression object representing the prepared expression

Throws:

XPathException - if the syntax of the expression is wrong, or if it references namespaces, variables, or functions that have not been declared.

createPattern

public XPathExpression createPattern(String pattern)
                              throws XPathException

Prepare (compile) an XSLT pattern for subsequent evaluation. The result is an XPathExpression object representing a (pseudo-) expression that when evaluated returns a boolean result: true if the context node matches the pattern, false if it does not.

Parameters:

pattern - the XSLT pattern to be compiled, supplied as a string

Returns:

an XPathExpression object representing the pattern, wrapped as an expression

Throws:

XPathException - if the syntax of the expression is wrong, or if it references namespaces, variables, or functions that have not been declared.

Since:

9.1

setNamespaceResolver

public void setNamespaceResolver(NamespaceResolver namespaceResolver)

Set the external namespace resolver to be used. The NamespaceResolver is stored as part of the static context. It overrides any namespaces declared directly using declareNamespace on the staticContext object

Parameters:

namespaceResolver - The namespace resolver, which maintains a mapping of prefixes to URIs. Any namespace prefix used in the XPath expression is resolved using this namespaceResolver.

getNamespaceResolver

public NamespaceResolver getNamespaceResolver()

Get the external namespace resolver, if one has been set using setNamespaceResolver(net.sf.saxon.om.NamespaceResolver)

Returns:

the namespace resolver supplied by the user if set, or a system-defined namespace resolver otherwise. By default, the IndependentContext object used as the XPathStaticContext also acts as the NamespaceResolver.

setDefaultElementNamespace

public void setDefaultElementNamespace(String uri)

Set the default namespace for elements and types

Parameters:

uri - The namespace to be used to qualify unprefixed element names and type names appearing in the XPath expression.