com.saxonica.ee.stream.adjunct

Class ChooseAdjunct

java.lang.Object

com.saxonica.ee.stream.adjunct.StreamingAdjunct

com.saxonica.ee.stream.adjunct.TransmissionAdjunct

com.saxonica.ee.stream.adjunct.ChooseAdjunct

All Implemented Interfaces:

FeedMaker

public class ChooseAdjunct
extends TransmissionAdjunct

Streaming code to implement a conditional ("if/choose") expression

Constructor Summary

Constructors

Constructor and Description
ChooseAdjunct()

Method Summary

Methods

Modifier and Type	Method and Description
FeedMaker	getFeedMaker(int arg) Get a FeedMaker, a factory class that creates a Feed to evaluate this expression in streaming mode.
WatchMaker	getWatchMaker(boolean forGrouping) Get a WatchMaker, a factory class that creates a Watch to evaluate this expression in streaming mode.
Feed	makeItemFeed(WatchManager watchManager, Feed out, XPathContext context)
Trigger	makeTransmissionFlow(WatchManager watchManager, Expression exp, Feed out, XPathContext context) Make a Trigger that implements this expression in streaming mode.
void	setExpression(Expression expression) Set the expression being processed by this StreamingAdjunct
Pattern	toStreamingPattern(Configuration config) Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

Methods inherited from class com.saxonica.ee.stream.adjunct.StreamingAdjunct

computeStreamability, getConfiguration, getDefaultFeedMaker, getExpression, setConfiguration

Methods inherited from class java.lang.Object

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

Constructor Detail

ChooseAdjunct

public ChooseAdjunct()

Method Detail

setExpression

public void setExpression(Expression expression)

Description copied from class: StreamingAdjunct

Set the expression being processed by this StreamingAdjunct

Overrides:

setExpression in class StreamingAdjunct

Parameters:

expression - the expression being processed

toStreamingPattern

public Pattern toStreamingPattern(Configuration config)

Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)

Overrides:

toStreamingPattern in class StreamingAdjunct

Parameters:

config - the Saxon configuration

Returns:

the equivalent pattern if conversion succeeds; otherwise null

getWatchMaker

public WatchMaker getWatchMaker(boolean forGrouping)
                         throws XPathException

Description copied from class: StreamingAdjunct

Get a WatchMaker, a factory class that creates a Watch to evaluate this expression in streaming mode. This method will only be called if the getImplementationMethod() method of the expression includes the value Expression.WATCH_METHOD

Overrides:

getWatchMaker in class TransmissionAdjunct

Parameters:

forGrouping - true if the selected items are being grouped

Returns:

a Watchmaker to evaluate the expression, or null if it is not streamable with respect to the specificed argument.

Throws:

XPathException - in the event of a failure

makeTransmissionFlow

public Trigger makeTransmissionFlow(WatchManager watchManager,
                           Expression exp,
                           Feed out,
                           XPathContext context)
                             throws XPathException

Description copied from class: TransmissionAdjunct

Make a Trigger that implements this expression in streaming mode. This method is used for an expression that is striding or crawling, and it delivers a Trigger connected to a sequence of Feeds which together have the effect of delivering a sequence of events and/or items that together represent the results of this instruction. This method MUST be implemented for every expression that has an operand whose usage is transmission (and for every such operand).

Overrides:

makeTransmissionFlow in class TransmissionAdjunct

Parameters:

watchManager - the WatchManager that fires this trigger

exp - the expression

out - the next action in the push pipeline for evaluation

context - the XPath dynamic context

Returns:

the Trigger (a Watch with a pattern)

Throws:

XPathException - if a dynamic evaluation error occurs.

makeItemFeed

public Feed makeItemFeed(WatchManager watchManager,
                Feed out,
                XPathContext context)
                  throws XPathException

Throws:

XPathException

getFeedMaker

public FeedMaker getFeedMaker(int arg)
                       throws XPathException

Description copied from class: StreamingAdjunct

Get a FeedMaker, a factory class that creates a Feed to evaluate this expression in streaming mode. In many cases the StreamingAdjunct is itself a FeedMaker, in which case it returns itself. But where an expression has several operands, it will typically create different feeds depending on which argument is the streamed input, and in such cases the individual StreamingAdjunct makes the decision which feed to use, by returning an appropriate FeedMaker.

Overrides:

getFeedMaker in class StreamingAdjunct

Parameters:

arg - identifies the argument with respect to which the expression is to be inverted: usually 0 to indicate the first argument is the value that is streamed. Argument numbering is the same as the sequence of arguments/operands returned by the method Expression.operands()

Returns:

a FeedMaker to evaluate the expression, or null if it is not streamable with respect to the specificed argument.

Throws:

XPathException - in the event of a failure