Package 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 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 Details

  • Method Details

    • 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