com.saxonica.stream.feed
Class ItemFeed

java.lang.Object
  com.saxonica.stream.feed.ItemFeed

All Implemented Interfaces:

Feed

Direct Known Subclasses:

AdjacentTextNodeMergerFeed, AtomizerFeed, AvgFeed, BufferingFeed, CardinalityCheckingFeed, CountFeed, DistinctValuesFeed, EmptyTextNodeRemoverFeed, FilterExpressionFeed, ForEachFeed, GeneralComparisonFeed, ItemMappingFeed, MinimaxFeed, NextIterationFeed, SimpleNodeConstructorFeed, StringJoinFeed, SumFeed, WithParamFeed

public abstract class ItemFeed
extends 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

ItemFeed(Expression exp, Feed result, Stack<XPathContext> contextStack)

Method Summary

abstract void	append(Item item) Supply one item towards the streamed input of the expression
void	close() Finish evaluating the expression.
XPathContext	getContext() Get the dynamic evaluation context
Stack<XPathContext>	getContextStack()
Expression	getExpression() Get the expression being evaluated by this ItemFeed
PipelineConfiguration	getPipelineConfiguration() Get the pipeline configuration
Feed	getResult() Get the result, that is, the ItemFeed to which the items in the result of the expression should be supplied
void	open() Start evaluating the expression.
void	setPipelineConfiguration(PipelineConfiguration pipe) Set the pipeline configuration

Methods inherited from class java.lang.Object

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

Constructor Detail

ItemFeed

public ItemFeed(Expression exp,
                Feed result,
                Stack<XPathContext> contextStack)

Method Detail

getExpression

public Expression getExpression()

Get the expression being evaluated by this ItemFeed

Returns:

the expression being evaluated

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

getContextStack

public Stack<XPathContext> getContextStack()

open

public void open()
          throws XPathException

Start evaluating the expression. The default implementation does nothing.

Specified by:

open in interface Feed

Throws:

XPathException - if a dynamic error occurs

append

public abstract void append(Item item)
                     throws XPathException

Supply one item towards the streamed input of the expression

Specified by:

append in interface Feed

Parameters:

item - the item to be supplied

Throws:

XPathException - to report any failure

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