Package com.saxonica.ee.stream.watch

Class AccumulatorWatch

java.lang.Object

com.saxonica.ee.stream.watch.AbstractWatch

com.saxonica.ee.stream.watch.PatternWatch

com.saxonica.ee.stream.watch.AccumulatorWatch

All Implemented Interfaces:

Watch

public class AccumulatorWatch
extends PatternWatch

This watch implements a single accumulator in streaming mode. Unlike other watches, it is called to process every node in the stream; it then checks whether the accumulator has any rule that matches this node, and if so applies the next-value expression associated with that accumulator rule.

The class also provides methods to return the "before" and "after" values of the accumulator for a given node. These have to make provision (a) for handling error situations (where evaluation of the accumulator failed), and (b) for handling the case where the value is requested (by another accumulator) before it is available.

Constructor Summary

Constructors

Constructor	Description
AccumulatorWatch(Accumulator accumulator)

Method Summary

Modifier and Type	Method	Description
void	close()	The close() method is called immediately before the Watch is destroyed, that is, when the element whose declaration scopes the constraint implemented by this Watch goes out of scope.
void	endSelectedParentNode(Location locationId)	Signal that the endElement event has occurred for the element whose startElement event caused the Watch to be activated.
Accumulator	getAccumulator()
XPathContext	getContext()
Sequence	getPostDescentValue(FleetingNode node)
Sequence	getPreDescentValue(FleetingNode node)
Sequence	getPreDescentValueAtDepth(int depth)
boolean	isBeingComputed(AccumulatorFn.Phase phase)
void	open(Terminator terminator)	Open the watch.
void	processItem(Item item)	Signal that a node (other than an element) that matches the selection has been found.
void	setNodeStack(java.util.Stack<FleetingNode> stack)
void	setWatchManager(WatchManager watchManager)
Receiver	startSelectedParentNode(FleetingParentNode node, Location locationId)	Signal that an element has been found that matches the selection that this Watch is looking for.

Methods inherited from class com.saxonica.ee.stream.watch.PatternWatch

getAnchorNode, getSelection, matchesNode, matchesNodesOfKind, setAnchorNode, setSelection

Methods inherited from class com.saxonica.ee.stream.watch.AbstractWatch

getNamespaceResolver, getPipelineConfiguration, setNamespaceResolver, setPipelineConfiguration

Methods inherited from class java.lang.Object

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

Constructor Detail

AccumulatorWatch

public AccumulatorWatch(Accumulator accumulator)

Method Detail

getAccumulator

public Accumulator getAccumulator()

getContext

public XPathContext getContext()

open

public void open(Terminator terminator)
          throws XPathException

Description copied from class: PatternWatch

Open the watch. This is done at the point where it first starts watching for nodes that match the selection.

Specified by:

open in interface Watch

Overrides:

open in class PatternWatch

Parameters:

terminator - action to be taken on failure

Throws:

XPathException - May be raised if a dynamic error occurs

setNodeStack

public void setNodeStack(java.util.Stack<FleetingNode> stack)

setWatchManager

public void setWatchManager(WatchManager watchManager)

startSelectedParentNode

public Receiver startSelectedParentNode(FleetingParentNode node,
                                        Location locationId)
                                 throws XPathException

Signal that an element has been found that matches the selection that this Watch is looking for. This method is called by the WatchManager while processing the startElement event that matches the selection. For this purpose, any attributes selected by the last step in the selection are ignored

Parameters:

node - the element or document node whose start event has been matched

locationId - the location associated with the element or document node (may be the location of the instruction that created it)

Returns:

always null

Throws:

ValidationException - May be raised if the constraint implemented by this Watch is violated @param locationId the location of the node in the source, or of the instruction that created it

XPathException - May be raised if a dynamic error occurs

isBeingComputed

public boolean isBeingComputed(AccumulatorFn.Phase phase)

processItem

public void processItem(Item item)
                 throws XPathException

Signal that a node (other than an element) that matches the selection has been found.

Specified by:

processItem in interface Watch

Overrides:

processItem in class PatternWatch

Parameters:

item - the node that was matched.

Throws:

XPathException - May be raised if a dynamic error occurs

endSelectedParentNode

public void endSelectedParentNode(Location locationId)
                           throws XPathException

Signal that the endElement event has occurred for the element whose startElement event caused the Watch to be activated.

Parameters:

locationId - the location of the parsing event

Throws:

ValidationException - May be raised if the constraint implemented by this Watch is violated @param locationId the location of the node in the source, or of the instruction that created it

XPathException - May be raised if a constraint implemented by this Watch is violated

close

public void close()
           throws XPathException

Description copied from class: PatternWatch

The close() method is called immediately before the Watch is destroyed, that is, when the element whose declaration scopes the constraint implemented by this Watch goes out of scope. The default implementation does nothing.

Specified by:

close in interface Watch

Overrides:

close in class PatternWatch

Throws:

XPathException - May be raised if a dynamic error occurs

getPreDescentValue

public Sequence getPreDescentValue(FleetingNode node)
                            throws XPathException

Throws:

XPathException

getPreDescentValueAtDepth

public Sequence getPreDescentValueAtDepth(int depth)
                                   throws XPathException

Throws:

XPathException

getPostDescentValue

public Sequence getPostDescentValue(FleetingNode node)
                             throws XPathException

Throws:

XPathException