Package com.saxonica.ee.stream.watch

Class AccumulatorWatch

java.lang.Object
com.saxonica.ee.stream.watch.AbstractWatch
com.saxonica.ee.stream.watch.PatternWatch
com.saxonica.ee.stream.watch.AccumulatorWatch
All Implemented Interfaces:
Watch
public class AccumulatorWatch extends PatternWatch
This watch implements a single accumulator in streaming mode. Unlike other watches, it is called to process every node in the stream; it then checks whether the accumulator has any rule that matches this node, and if so applies the next-value expression associated with that accumulator rule.

The class also provides methods to return the "before" and "after" values of the accumulator for a given node. These have to make provision (a) for handling error situations (where evaluation of the accumulator failed), and (b) for handling the case where the value is requested (by another accumulator) before it is available.

  • Constructor Details

    • AccumulatorWatch

      public AccumulatorWatch(Accumulator accumulator)

  • Method Details

    • getAccumulator

      public Accumulator getAccumulator()

    • getContext

      public XPathContext getContext()

    • open

      public void open(Terminator terminator) throws XPathException
      Description copied from class: PatternWatch
      Open the watch. This is done at the point where it first starts watching for nodes that match the selection.
      Specified by:
      open in interface Watch
      Overrides:
      open in class PatternWatch
      Parameters:
      terminator - action to be taken on failure
      Throws:
      XPathException - May be raised if a dynamic error occurs

    • setNodeStack

      public void setNodeStack(Stack<FleetingNode> stack)

    • setWatchManager

      public void setWatchManager(WatchManager watchManager)

    • startSelectedParentNode

      public Receiver startSelectedParentNode(FleetingParentNode node, Location locationId) throws XPathException
      Signal that an element has been found that matches the selection that this Watch is looking for. This method is called by the WatchManager while processing the startElement event that matches the selection. For this purpose, any attributes selected by the last step in the selection are ignored
      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:
      always null
      Throws:
      ValidationException - May be raised if the constraint implemented by this Watch is violated @param locationId the location of the node in the source, or of the instruction that created it
      XPathException - May be raised if a dynamic error occurs

    • isBeingComputed

      public boolean isBeingComputed(AccumulatorFn.Phase phase)

    • processItem

      public void processItem(Item item) throws XPathException
      Signal that a node (other than an element) that matches the selection has been found.
      Specified by:
      processItem in interface Watch
      Overrides:
      processItem in class PatternWatch
      Parameters:
      item - the node that was matched.
      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.
      Parameters:
      locationId - the location of the parsing event
      Throws:
      ValidationException - May be raised if the constraint implemented by this Watch is violated @param locationId the location of the node in the source, or of the instruction that created it
      XPathException - May be raised if a constraint implemented by this Watch is violated

    • close

      public void close() throws XPathException
      Description copied from class: PatternWatch
      The close() method is called immediately before the Watch is destroyed, that is, when the element whose declaration scopes the constraint implemented by this Watch goes out of scope. The default implementation does nothing.
      Specified by:
      close in interface Watch
      Overrides:
      close in class PatternWatch
      Throws:
      XPathException - May be raised if a dynamic error occurs

    • getPreDescentValue

      public Sequence getPreDescentValue(FleetingNode node) throws XPathException
      Throws:
      XPathException

    • getPreDescentValueAtDepth

      public Sequence getPreDescentValueAtDepth(int depth) throws XPathException
      Throws:
      XPathException

    • getPostDescentValue

      public Sequence getPostDescentValue(FleetingNode node) throws XPathException
      Throws:
      XPathException