com.saxonica.ee.stream.feed

Class ItemFeed

java.lang.Object

com.saxonica.ee.stream.feed.ItemFeed

All Implemented Interfaces:

Feed

Direct Known Subclasses:

AbsorptionFeed, ApplyTemplatesAction, ApplyTemplatesFeed, BooleanFnStreamer.BooleanFnFeed, BufferingFeed, BufferingFilterExpressionFeed, CallableFeed, CardinalityCheckingFeed, ComplexNodeEventFeed, ConditionalBlockAdjunct.ConditionalBlockFeed, FeedToReceiver, FilteringFeed, ForEachAction, ForEachGroupPartitionAction, ForExpressionAdjunct.ForExpressionFeed, ForkAdjunct.FeedToOutputter, GeneralComparisonFeed, ItemCheckingFeed, ItemMappingFeed, LiteralAdjunct.LiteralItemFeed, MotionlessFeed, NextIterationFeed, NoCloseFeed, NoOpenFeed, NoOpenOrCloseFeed, ShallowCopyEventFeed, SimpleNodeConstructorFeed, TryCatchAdjunct.TryCatchFeed

public abstract class ItemFeed
extends java.lang.Object
implements Feed

An ItemFeed evaluates an expression in "composed push" mode. Its streaming input is supplied via a sequence of append() calls that supply individual (composed) items in the input sequence, and its output is (in most cases) delivered via a sequence of append() calls to the feed representing the parent expression. The exception is the FeedToReceiver class which appends the supplied items to a Receiver.

Every kind of expression can be evaluated using an ItemFeed. The ItemFeed is obtained by calling getFeedMaker() on the ExpressionCompiler corresponding to the class of expression. The expression must have been previously marked to indicate which of its inputs is being supplied in streaming mode.

Constructor Summary

Constructors

Constructor and Description
ItemFeed(Expression exp, Feed result, XPathContext context)
ItemFeed(Feed result, XPathContext context)

Method Summary

Modifier and Type	Method and Description
void	close() Finish evaluating the expression.
void	dynamicError(XPathException error) Report a dynamic error.
void	endSelectedParentNode(Location locationId) Signal that the endElement event has occurred for the element whose startElement event caused the Watch to be activated.
XPathContext	getContext() Get the dynamic evaluation context
Expression	getExpression() Get the expression being evaluated by this ItemFeed.
PipelineConfiguration	getPipelineConfiguration() Get the pipeline configuration
SequenceReceiver	getReceiver() Get a receiver to which start and end events for documents and elements can be written.
Feed	getResult() Get the result, that is, the ItemFeed to which the items in the result of the expression should be supplied
Terminator	getTerminator() Get the Terminator which can be used to request early termination of the Feed
boolean	hasFailed()
void	open(Terminator terminator) Start evaluating the expression.
abstract void	processItem(Item item) Supply one item towards the streamed input of the expression
static void	processItems(SequenceIterator iter, Feed result) Convenience method to process all the items selected by an iterator and push them to the next feed in the push pipeline
void	setExpression(Expression exp) Set the expression being evaluated by this ItemFeed
void	setHasFailed() Mark this feed as having failed (that is, as having detected and reported a dynamic error).
void	setPipelineConfiguration(PipelineConfiguration pipe) Set the pipeline configuration
void	setTerminator(Terminator terminator) Provide a callback that can be used to request early termination of the streaming of this input document
Receiver	startSelectedParentNode(FleetingParentNode node, Location locationId) Signal that an element or document node has been found that matches the selection that this Watch is looking for.

Methods inherited from class java.lang.Object

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

Constructor Detail

ItemFeed

public ItemFeed(Feed result,
                XPathContext context)

ItemFeed

public ItemFeed(Expression exp,
                Feed result,
                XPathContext context)

Method Detail

processItems

public static void processItems(SequenceIterator iter,
                                Feed result)
                         throws XPathException

Convenience method to process all the items selected by an iterator and push them to the next feed in the push pipeline

Parameters:

iter - iterator over the selected items

result - the next feed in the pipeline

Throws:

XPathException - if any dynamic error occurs

setExpression

public void setExpression(Expression exp)

Set the expression being evaluated by this ItemFeed

Parameters:

exp - the relevant expression

getExpression

public Expression getExpression()

Get the expression being evaluated by this ItemFeed. May be null if not known or not relevant

Returns:

the expression being evaluated

setTerminator

public void setTerminator(Terminator terminator)

Provide a callback that can be used to request early termination of the streaming of this input document

Parameters:

terminator - the class that can be called to request termination

setHasFailed

public void setHasFailed()

Mark this feed as having failed (that is, as having detected and reported a dynamic error). Once the feed is marked as having failed, it should not attempt to process any further input.

getTerminator

public Terminator getTerminator()

Get the Terminator which can be used to request early termination of the Feed

Returns:

the Terminator that was passed to the open() call, or null if open() has not been called

getResult

public Feed getResult()

Get the result, that is, the ItemFeed to which the items in the result of the expression should be supplied

Returns:

the ItemFeed that consumes the results of this expression

setPipelineConfiguration

public void setPipelineConfiguration(PipelineConfiguration pipe)

Set the pipeline configuration

Parameters:

pipe - the pipeline configuration

getPipelineConfiguration

public PipelineConfiguration getPipelineConfiguration()

Get the pipeline configuration

Specified by:

getPipelineConfiguration in interface Feed

Returns:

the pipeline configuration

getContext

public XPathContext getContext()

Get the dynamic evaluation context

Returns:

the dynamic evaluation context

open

public void open(Terminator terminator)
          throws XPathException

Start evaluating the expression. The default implementation does nothing.

Specified by:

open in interface Feed

Parameters:

terminator - used to achieve early exit

Throws:

XPathException - if a dynamic error occurs

startSelectedParentNode

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

Signal that an element or document node has been found that matches the selection that this Watch is looking for. This method is called by the WatchManager while processing the startElement or startDocument event that matches the selection.

Specified by:

startSelectedParentNode in interface Feed

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:

a Receiver to be notified of all events starting with the startElement/startDocument event for the matched element, and ending with the endElement event for that element; or null if this feature is not required.

Throws:

XPathException - May be raised if a dynamic error occurs

processItem

public abstract void processItem(Item item)
                          throws XPathException

Supply one item towards the streamed input of the expression

Specified by:

processItem in interface Feed

Parameters:

item - the item to be supplied

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.

Specified by:

endSelectedParentNode in interface Feed

Parameters:

locationId - the location of the element

Throws:

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

close

public void close()
           throws XPathException

Finish evaluating the expression. The default implementation does nothing.

Specified by:

close in interface Feed

Throws:

XPathException - if a dynamic error occurs

getReceiver

public SequenceReceiver getReceiver()

Get a receiver to which start and end events for documents and elements can be written.

Specified by:

getReceiver in interface Feed

Returns:

the receiver

dynamicError

public void dynamicError(XPathException error)
                  throws XPathException

Report a dynamic error. This requires searching up the "feed" pipeline to see if there is a try/catch expression interested in being notified of this error; if there is none, the error is thrown as an exception

Parameters:

error - the exception representing the dynamic error

Throws:

XPathException - if there is no try/catch expression wanting to catch this error

hasFailed

public boolean hasFailed()