net.sf.saxon.xpath
Class XPathEvaluator

java.lang.Object
  net.sf.saxon.xpath.XPathEvaluator

All Implemented Interfaces:

XPath

public class XPathEvaluator
extends Object
implements XPath

XPathEvaluator provides a simple API for standalone XPath processing (that is, executing XPath expressions in the absence of an XSLT stylesheet). It is an implementation of the JAXP 1.3 XPath interface, with additional methods provided (a) for backwards compatibility (b) to give extra control over the XPath evaluation, and (c) to support XPath 2.0.

It is intended to evolve this so that it only supports the JAXP style of operation. Some of the methods are therefore marked as deprecated in this release, and will be dropped in a future release.

For an alternative XPath API, offering more direct access to Saxon capabilities, see XPathEvaluator.

Note that the XPathEvaluator links to a Saxon Configuration object. By default a new Configuration is created automatically. In many applications, however, it is desirable to share a configuration. The default configuration is not schema aware. All source documents used by XPath expressions under this evaluator must themselves be built using the Configuration used by this evaluator.

Author:

Michael H. Kay

Constructor Summary

XPathEvaluator()
Default constructor.

XPathEvaluator(Configuration config)
Construct an XPathEvaluator with a specified configuration.

XPathEvaluator(Source source)
Construct an XPathEvaluator to process a particular source document.

Method Summary

XPathExpression	compile(String expr) Compile an XPath 2.0 expression
XPathExpressionImpl	createExpression(String expression) Deprecated. since Saxon 8.9 - use compile(String)
List	evaluate(String expression) Deprecated. since Saxon 8.9 - use the various method defined in the JAXP interface definition
String	evaluate(String expr, InputSource inputSource) Single-shot method to parse and build a source document, and compile an execute an XPath 2.0 expression, against that document, returning the result as a string
Object	evaluate(String expr, InputSource inputSource, QName qName) Single-shot method to parse and build a source document, and compile an execute an XPath 2.0 expression, against that document
String	evaluate(String expr, Object node) Single-shot method to compile an execute an XPath 2.0 expression, returning the result as a string.
Object	evaluate(String expr, Object node, QName qName) Single-shot method to compile and execute an XPath 2.0 expression.
Object	evaluateSingle(String expression) Deprecated. since Saxon 8.9 - use the methods defined in the JAXP interface
Configuration	getConfiguration() Get the Configuration used by this XPathEvaluator
Executable	getExecutable() Get the executable
NamespaceContext	getNamespaceContext() Get the namespace context, if one has been set using setNamespaceContext(javax.xml.namespace.NamespaceContext)
JAXPXPathStaticContext	getStaticContext() Get the current static context
XPathFunctionResolver	getXPathFunctionResolver() Get the resolver for XPath functions
XPathVariableResolver	getXPathVariableResolver() Get the resolver for XPath variables
void	importSchema(Source source) Import a schema.
boolean	isBackwardsCompatible() Get the value of XPath 1.0 compatibility mode
static void	main(String[] args) A simple command-line interface for the XPathEvaluator (not documented).
void	reset()
void	setBackwardsCompatible(boolean compatible) Set XPath 1.0 compatibility mode on or off (by default, it is false).
void	setContextNode(NodeInfo node) Deprecated. since Saxon 8.9 - use the various method defined in the JAXP interface definition, which allow a NodeInfo object to be supplied as the value of the Source argument
void	setNamespaceContext(NamespaceContext namespaceContext) Set the namespace context to be used.
NodeInfo	setSource(Source source) Supply the document against which XPath expressions are to be executed.
void	setStaticContext(JAXPXPathStaticContext context) Set the static context for compiling XPath expressions.
void	setStripSpace(boolean strip) Deprecated. since 8.9. The preferred way to define options for the way in which source documents are built is to use the class AugmentedSource for any of the methods expecting a Source object.
void	setXPathFunctionResolver(XPathFunctionResolver xPathFunctionResolver) Set the resolver for XPath functions
void	setXPathVariableResolver(XPathVariableResolver xPathVariableResolver) Set the resolver for XPath variables

Methods inherited from class java.lang.Object

equals, 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. The default Configuration is not schema-aware.

XPathEvaluator

public XPathEvaluator(Configuration config)

Construct an XPathEvaluator with a specified configuration.

Parameters:

config - the configuration to be used. If schema-aware XPath expressions are to be used, this must be a SchemaAwareConfiguration.

XPathEvaluator

public XPathEvaluator(Source source)
               throws XPathException

Construct an XPathEvaluator to process a particular source document. This is equivalent to using the default constructor and immediately calling setSource().

Parameters:

source - The source document (or a specific node within it).

Throws:

XPathException

Method Detail

getConfiguration

public Configuration getConfiguration()

Get the Configuration used by this XPathEvaluator

Returns:

the Configuration used by this XPathEvaluator

setStripSpace

public void setStripSpace(boolean strip)

Deprecated. since 8.9. The preferred way to define options for the way in which source documents are built is to use the class AugmentedSource for any of the methods expecting a Source object.

Indicate whether all whitespace text nodes in the source document are to be removed. This option has no effect unless it is called before the call on setSource(), and unless the Source supplied to setSource() is a SAXSource or StreamSource.

Parameters:

strip - True if all whitespace text nodes are to be stripped from the source document, false otherwise. The default if the method is not called is false.

setSource

public NodeInfo setSource(Source source)
                   throws XPathException

Supply the document against which XPath expressions are to be executed. This method must be called before preparing or executing an XPath expression. Setting a new source document clears all the namespaces that have been declared.

Parameters:

source - Any javax.xml.transform.Source object representing the document against which XPath expressions will be executed. Note that a Saxon DocumentInfo (indeed any NodeInfo) can be used as a Source. To use a third-party DOM Document as a source, create an instance of DOMSource to wrap it.

The Source object supplied also determines the initial setting of the context item. In most cases the context node will be the root of the supplied document; however, if a NodeInfo or DOMSource is supplied it can be any node in the document.

Returns:

the NodeInfo of the start node in the resulting document object.

Throws:

XPathException

setStaticContext

public void setStaticContext(JAXPXPathStaticContext context)

Set the static context for compiling XPath expressions. This provides 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 JAXPXPathStaticContext 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 static context

Throws:

IllegalArgumentException - if the supplied static context uses a different and incompatible Configuration from the one used in this XPathEvaluator

getStaticContext

public JAXPXPathStaticContext getStaticContext()

Get the current static context

Returns:

the static context

getExecutable

public Executable getExecutable()

Get the executable

Returns:

the executable

createExpression

public XPathExpressionImpl createExpression(String expression)
                                     throws XPathException

Deprecated. since Saxon 8.9 - use compile(String)

Prepare an XPath expression for subsequent evaluation.

Parameters:

expression - The XPath expression to be evaluated, 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.

setContextNode

public void setContextNode(NodeInfo node)

Deprecated. since Saxon 8.9 - use the various method defined in the JAXP interface definition, which allow a NodeInfo object to be supplied as the value of the Source argument

Set the context node. This provides the context node for any expressions executed after this method is called, including expressions that were prepared before it was called.

Parameters:

node - The node to be used as the context node. The node must be within a tree built using the same Saxon Configuration as used by this XPathEvaluator.

Throws:

IllegalArgumentException - if the supplied node was built using the wrong Configuration

evaluate

public List evaluate(String expression)
              throws XPathException

Deprecated. since Saxon 8.9 - use the various method defined in the JAXP interface definition

Prepare and execute an XPath expression, supplied as a string, and returning the results as a List.

Parameters:

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

Returns:

The results of the expression, as a List. The List represents the sequence of items returned by the expression. Each item in the list will either be an object representing a node, or a Java object representing an atomic value. The types of Java object that may be included in the list, and the XML Schema data types that they correspond to, are as follows:

• Boolean (xs:boolean)
• String (xs:string)
• BigDecimal (xs:decimal)
• Long (xs:integer and its derived types)
• Double (xs:double)
• Float (xs:float)
• Date (xs:date, xs:dateTime)

Throws:

XPathException

reset

public void reset()

Specified by:

reset in interface XPath

setBackwardsCompatible

public void setBackwardsCompatible(boolean compatible)

Set XPath 1.0 compatibility mode on or off (by default, it is false). This applies to any XPath expression compiled while this option is in force.

Parameters:

compatible - true if XPath 1.0 compatibility mode is to be set to true, false if it is to be set to false.

isBackwardsCompatible

public boolean isBackwardsCompatible()

Get the value of XPath 1.0 compatibility mode

Returns:

true if XPath 1.0 compatibility mode is set

setXPathVariableResolver

public void setXPathVariableResolver(XPathVariableResolver xPathVariableResolver)

Set the resolver for XPath variables

Specified by:

setXPathVariableResolver in interface XPath

Parameters:

xPathVariableResolver - a resolver for variables

getXPathVariableResolver

public XPathVariableResolver getXPathVariableResolver()

Get the resolver for XPath variables

Specified by:

getXPathVariableResolver in interface XPath

Returns:

the resolver, if one has been set

setXPathFunctionResolver

public void setXPathFunctionResolver(XPathFunctionResolver xPathFunctionResolver)

Set the resolver for XPath functions

Specified by:

setXPathFunctionResolver in interface XPath

Parameters:

xPathFunctionResolver - a resolver for XPath function calls

getXPathFunctionResolver

public XPathFunctionResolver getXPathFunctionResolver()

Get the resolver for XPath functions

Specified by:

getXPathFunctionResolver in interface XPath

Returns:

the resolver, if one has been set

setNamespaceContext

public void setNamespaceContext(NamespaceContext namespaceContext)

Set the namespace context to be used.

Specified by:

setNamespaceContext in interface XPath

Parameters:

namespaceContext - The namespace context

getNamespaceContext

public NamespaceContext getNamespaceContext()

Get the namespace context, if one has been set using setNamespaceContext(javax.xml.namespace.NamespaceContext)

Specified by:

getNamespaceContext in interface XPath

Returns:

the namespace context if set, or null otherwise

importSchema

public void importSchema(Source source)
                  throws SchemaException

Import a schema. This is possible only if the schema-aware version of Saxon is being used, and if the Configuration is a SchemaAwareConfiguration. Having imported a schema, the types defined in that schema become part of the static context.

Parameters:

source - A Source object identifying the schema document to be loaded

Throws:

SchemaException - if the schema contained in this document is invalid

UnsupportedOperationException - if the configuration is not schema-aware

compile

public XPathExpression compile(String expr)
                        throws XPathExpressionException

Compile an XPath 2.0 expression

Specified by:

compile in interface XPath

Parameters:

expr - the XPath 2.0 expression to be compiled, as a string

Returns:

the compiled form of the expression

Throws:

XPathExpressionException - if there are any static errors in the expression. Note that references to undeclared variables are not treated as static errors, because variables are not pre-declared using this API.

evaluate

public Object evaluate(String expr,
                       Object node,
                       QName qName)
                throws XPathExpressionException

Single-shot method to compile and execute an XPath 2.0 expression.

Specified by:

evaluate in interface XPath

Parameters:

expr - The XPath 2.0 expression to be compiled and executed

node - The context node for evaluation of the expression.

This may be a NodeInfo object, representing a node in Saxon's native implementation of the data model, or it may be a node in any supported external object model: DOM, JDOM, DOM4J, or XOM, or any other model for which support has been configured in the Configuration. Note that the supporting libraries for the chosen model must be on the class path.

Contrary to the interface specification, Saxon does not supply an empty document when the value is null. This is because Saxon supports multiple object models, and it's unclear what kind of document node would be appropriate. Instead, Saxon uses the node supplied to the setContextNode(net.sf.saxon.om.NodeInfo) method if available, and if none is available, executes the XPath expression with the context item undefined.

qName - The type of result required. For details, see XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)

Returns:

the result of evaluating the expression, returned as described in XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)

Throws:

XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.

evaluate

public String evaluate(String expr,
                       Object node)
                throws XPathExpressionException

Single-shot method to compile an execute an XPath 2.0 expression, returning the result as a string.

Specified by:

evaluate in interface XPath

Parameters:

expr - The XPath 2.0 expression to be compiled and executed

node - The context node for evaluation of the expression

This may be a NodeInfo object, representing a node in Saxon's native implementation of the data model, or it may be a node in any supported external object model: DOM, JDOM, DOM4J, or XOM, or any other model for which support has been configured in the Configuration. Note that the supporting libraries for the chosen model must be on the class path.

Contrary to the interface specification, Saxon does not supply an empty document when the value is null. This is because Saxon supports multiple object models, and it's unclear what kind of document node would be appropriate. Instead, Saxon uses the node supplied to the setContextNode(net.sf.saxon.om.NodeInfo) method if available, and if none is available, executes the XPath expression with the context item undefined.

Returns:

the result of evaluating the expression, converted to a string as if by calling the XPath string() function

Throws:

XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.

evaluate

public Object evaluate(String expr,
                       InputSource inputSource,
                       QName qName)
                throws XPathExpressionException

Single-shot method to parse and build a source document, and compile an execute an XPath 2.0 expression, against that document

Specified by:

evaluate in interface XPath

Parameters:

expr - The XPath 2.0 expression to be compiled and executed

inputSource - The source document: this will be parsed and built into a tree, and the XPath expression will be executed with the root node of the tree as the context node.

qName - The type of result required. For details, see XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)

Returns:

the result of evaluating the expression, returned as described in XPathExpressionImpl.evaluate(Object, javax.xml.namespace.QName)

Throws:

XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.

NullPointerException - if any of the three arguments is null

evaluate

public String evaluate(String expr,
                       InputSource inputSource)
                throws XPathExpressionException

Single-shot method to parse and build a source document, and compile an execute an XPath 2.0 expression, against that document, returning the result as a string

Specified by:

evaluate in interface XPath

Parameters:

expr - The XPath 2.0 expression to be compiled and executed

inputSource - The source document: this will be parsed and built into a tree, and the XPath expression will be executed with the root node of the tree as the context node

Returns:

the result of evaluating the expression, converted to a string as if by calling the XPath string() function

Throws:

XPathExpressionException - if any static or dynamic error occurs in evaluating the expression.

NullPointerException - if either of the two arguments is null

evaluateSingle

public Object evaluateSingle(String expression)
                      throws XPathException

Deprecated. since Saxon 8.9 - use the methods defined in the JAXP interface

Prepare and execute an XPath expression, supplied as a string, and returning the first item in the result. This is useful where it is known that the expression will only return a singleton value (for example, a single node, or a boolean).

Parameters:

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

Returns:

The first item in the sequence returned by the expression. If the expression returns an empty sequence, this method returns null. Otherwise, it returns the first item in the result sequence, represented as a Java object using the same mapping as for the evaluate() method

Throws:

XPathException

main

public static void main(String[] args)
                 throws Exception

A simple command-line interface for the XPathEvaluator (not documented).

Parameters:

args - command line arguments. First parameter is the filename containing the source document, second parameter is the XPath expression.

Throws:

Exception