com.saxonica.ee.stream.adjunct

Class GroupBoundaryTester

java.lang.Object

com.saxonica.ee.stream.adjunct.GroupBoundaryTester

Direct Known Subclasses:

GroupAdjacentTester, GroupEndingTester, GroupStartingTester

public abstract class GroupBoundaryTester
extends java.lang.Object

This feed supports xsl:for-each-group in streaming mode. It is supplied with all the nodes selected by the xsl:for-each-group instruction (in composed form); it decides whether a node is the first in a new group, and if so, triggers the start/end-of-group actions. It also feeds every node into a push pipeline that reflects the processing of the "current-group" variable.

The items received by this Feed will generally be supplied by a CopyOfWatch. There is scope for future optimization to prevent the selected nodes being unnecessarily composed in memory.

There are thus two destinations into which this class feeds. The first, identified by the usual result variable, receives every item in the group, and is notified of the start and end of a group by calling its open() and close() methods. This destination processes the instructions within the for-each-group instruction before and after the reference to the grouping variable. The second destination, identified by the variable outerFeed, has its open() method called at the beginning of processing the population, and its close() method called at the end of processing the population; its append() method is called with the items that result from evaluation of the for-each-group body.

Constructor Summary

Constructors

Constructor and Description
GroupBoundaryTester(ForEachGroup expression, XPathContext context)

Method Summary

Modifier and Type	Method and Description
ForEachGroup	getControllingExpression()
protected XPathContext	getLocalContext()
abstract boolean	notifyItem() Signal that a new item that matches the selection has been found.
void	setControllingExpression(ForEachGroup controllingExpression)

Methods inherited from class java.lang.Object

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

Constructor Detail

GroupBoundaryTester

public GroupBoundaryTester(ForEachGroup expression,
                           XPathContext context)

Method Detail

getLocalContext

protected XPathContext getLocalContext()

setControllingExpression

public void setControllingExpression(ForEachGroup controllingExpression)

getControllingExpression

public ForEachGroup getControllingExpression()

notifyItem

public abstract boolean notifyItem()
                            throws XPathException

Signal that a new item that matches the selection has been found. The new item will be the context item (and its position will be the context position) in the current iterator of the supplied context object

Returns:

true if this item is the start of a new group

Throws:

XPathException - May be raised if a dynamic error occurs