net.sf.saxon.sxpath
Class XPathExpression

java.lang.Object
  net.sf.saxon.sxpath.XPathExpression

All Implemented Interfaces:

Serializable

public class XPathExpression
extends Object
implements Serializable

This class is a representation of an XPath Expression for use with the XPathEvaluator class. It is modelled on the XPath API defined in JAXP 1.3, but is cut down to remove any dependencies on JAXP 1.3, making it suitable for use on vanilla JDK 1.4 installations.

Author:

Michael H. Kay

See Also:

Serialized Form

Constructor Summary

protected

XPathExpression(XPathEvaluator evaluator, Expression exp) The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator

Method Summary

XPathDynamicContext	createDynamicContext(Controller controller, Item contextItem) Create a dynamic context suitable for evaluating this expression within an environement represented by an existing controller.
XPathDynamicContext	createDynamicContext(Item contextItem) Create a dynamic context suitable for evaluating this expression
boolean	effectiveBooleanValue(XPathDynamicContext context) Evaluate the expression, returning its effective boolean value
List	evaluate(Source source) Execute a prepared XPath expression, returning the results as a List in which items have been converted to the appropriate Java object.
List	evaluate(XPathDynamicContext context) Execute the expression, returning the result as a List, whose members will be instances of the class Item
Object	evaluateSingle(Source source) Execute a prepared XPath expression, returning the first item in the result.
Item	evaluateSingle(XPathDynamicContext context) Execute the expression, returning the result as a single Item If the result of the expression is a sequence containing more than one item, items after the first are discarded.
Expression	getInternalExpression() Low-level method to get the internal Saxon expression object.
SequenceIterator	iterate(XPathDynamicContext context) Execute the expression, returning the result as a SequenceIterator, whose members will be instances of the class Item
SequenceIterator	rawIterator(Source source) Deprecated. since 8.9 - use iterate(net.sf.saxon.sxpath.XPathDynamicContext)
protected void	setStackFrameMap(SlotManager map, int numberOfExternalVariables) Define the number of slots needed for local variables within the expression

Methods inherited from class java.lang.Object

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

Constructor Detail

XPathExpression

protected XPathExpression(XPathEvaluator evaluator,
                          Expression exp)

The constructor is protected, to ensure that instances can only be created using the createExpression() method of XPathEvaluator

Parameters:

evaluator - the creating XPathEvaluator

exp - the internal representation of the compiled expression

Method Detail

setStackFrameMap

protected void setStackFrameMap(SlotManager map,
                                int numberOfExternalVariables)

Define the number of slots needed for local variables within the expression

Parameters:

map - the stack frame map identifying all the variables used by the expression, both those declared internally, and references to variables declared externally

numberOfExternalVariables - the number of slots in the stack frame allocated to externally-declared variables. These must be assigned a value before execution starts

createDynamicContext

public XPathDynamicContext createDynamicContext(Item contextItem)

Create a dynamic context suitable for evaluating this expression

Parameters:

contextItem - the initial context item, which may be null if no context item is required, or if it is to be supplied later

Returns:

an XPathDynamicContext object representing a suitable dynamic context. This will be initialized with a stack frame suitable for holding the variables used by the expression.

createDynamicContext

public XPathDynamicContext createDynamicContext(Controller controller,
                                                Item contextItem)
                                         throws XPathException

Create a dynamic context suitable for evaluating this expression within an environement represented by an existing controller. The dynamic context will inherit properties of the Controller such as the current error listener, URI resolver, document pool, and implicit timezone.

Parameters:

controller - an existing controller. May be null, in which case the method is equivalent to calling createDynamicContext(net.sf.saxon.om.Item)

contextItem - the initial context item, which may be null if no context item is required, or if it is to be supplied later

Returns:

an XPathDynamicContext object representing a suitable dynamic context. This will be initialized with a stack frame suitable for holding the variables used by the expression.

Throws:

XPathException

Since:

9.2

iterate

public SequenceIterator iterate(XPathDynamicContext context)
                         throws XPathException

Execute the expression, returning the result as a SequenceIterator, whose members will be instances of the class Item

Note that if evaluation of the expression fails with a dynamic error, this will generally be reported in the form of an exception thrown by the next() method of the SequenceIterator

Parameters:

context - the XPath dynamic context

Returns:

an iterator over the result of the expression

Throws:

XPathException

evaluate

public List evaluate(XPathDynamicContext context)
              throws XPathException

Execute the expression, returning the result as a List, whose members will be instances of the class Item

Parameters:

context - the XPath dynamic context

Returns:

a list of items representing the result of the expression

Throws:

XPathException

evaluateSingle

public Item evaluateSingle(XPathDynamicContext context)
                    throws XPathException

Execute the expression, returning the result as a single Item If the result of the expression is a sequence containing more than one item, items after the first are discarded. If the result is an empty sequence, the method returns null.

Parameters:

context - the XPath dynamic context

Returns:

the first item in the result of the expression, or null

Throws:

XPathException

effectiveBooleanValue

public boolean effectiveBooleanValue(XPathDynamicContext context)
                              throws XPathException

Evaluate the expression, returning its effective boolean value

Parameters:

context - the XPath dynamic context

Returns:

the effective boolean value of the result, as defined by the fn:boolean() function

Throws:

XPathException - if a dynamic error occurs, or if the result is a value for which no effective boolean value is defined

evaluate

public List evaluate(Source source)
              throws XPathException

Execute a prepared XPath expression, returning the results as a List in which items have been converted to the appropriate Java object.

Parameters:

source - the document or other node against which the XPath expression will be evaluated. This may be a Saxon NodeInfo object, representing a node in an existing tree, or it may be any kind of JAXP Source object such as a StreamSource SAXSource or DOMSource. For the way in which the source document is built, see Configuration.buildDocument(javax.xml.transform.Source)

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 instance of net.sf.saxon.om.NodeInfo, representing a node, or a Java object representing an atomic value.

Throws:

XPathException

evaluateSingle

public Object evaluateSingle(Source source)
                      throws XPathException

Execute a prepared XPath expression, 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:

source - the document or other node against which the XPath expression will be evaluated. This may be a Saxon NodeInfo object, representing a node in an existing tree, or it may be any kind of JAXP Source object such as a StreamSource SAXSource or DOMSource. For the way in which the source document is built, see Configuration.buildDocument(javax.xml.transform.Source)

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

rawIterator

public SequenceIterator rawIterator(Source source)
                             throws XPathException

Deprecated. since 8.9 - use iterate(net.sf.saxon.sxpath.XPathDynamicContext)

Get a raw iterator over the results of the expression. This returns results without any conversion of the returned items to "native" Java classes. This method is intended for use by applications that need to process the results of the expression using internal Saxon interfaces.

Parameters:

source - the document or other node against which the XPath expression will be evaluated. This may be a Saxon NodeInfo object, representing a node in an existing tree, or it may be any kind of JAXP Source object such as a StreamSource SAXSource or DOMSource. For the way in which the source document is built, see Configuration.buildDocument(javax.xml.transform.Source)

Returns:

an iterator over the results of the expression

Throws:

XPathException

getInternalExpression

public Expression getInternalExpression()

Low-level method to get the internal Saxon expression object. This exposes a wide range of internal methods that may be needed by specialized applications, and allows greater control over the dynamic context for evaluating the expression.

Returns:

the underlying Saxon expression object.