## com.saxonica.stream.watch
Class VoidWatch

    java.lang.Object
      com.saxonica.validate.AbstractWatch
          com.saxonica.stream.watch.ComposingWatch
              com.saxonica.stream.watch.VoidWatch

All Implemented Interfaces:
  Watch

Direct Known Subclasses:
  NonstreamingExpressionWatch

    public class VoidWatch

extends ComposingWatch

This class is a Watch that always returns an empty sequence as its result.

Constructor Summary
`VoidWatch(Feed result, Stack<XPathContext> contextStack)` Create the singleton VoidWatch

Method Summary
`void` `endSelectedParentNode(int locationId)` Signal that the endElement event has occurred for the element whose startElement event caused the Watch to be activated.
`void` `notifySelectedLeafNode(FleetingNode node, int locationId)` Signal that a node (other than an element) that matches the selection has been found.
`Receiver` `startSelectedParentNode(FleetingNode node, int locationId)` Signal that an element has been found that matches the selection that this Watch is looking for.

Methods inherited from class com.saxonica.stream.watch.ComposingWatch
`close, getContext, getContextStack, getResult, open`

Methods inherited from class com.saxonica.validate.AbstractWatch
`getAnchorNode, getNamespaceResolver, getPipelineConfiguration, getSelection, setAnchorNode, setNamespaceResolver, setPipelineConfiguration, setSelection`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### VoidWatch

    public VoidWatch(Feed result,
                     Stack<XPathContext> contextStack)

  Create the singleton VoidWatch

Method Detail

### startSelectedParentNode

    public Receiver startSelectedParentNode(FleetingNode node,
                                            int 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:
    a Receiver to be notified of all events starting with the startElement/startDocument event for the matched element, and ending with the endElement event for that element.
  Throws:
    `ValidationException` - May be raised if the constraint implemented by this Watch is violated @param locationId
    `XPathException`

### notifySelectedLeafNode

    public void notifySelectedLeafNode(FleetingNode node,
                                       int locationId)
                                throws XPathException

  Signal that a node (other than an element) that matches the selection has been found.

  Specified by:
    `notifySelectedLeafNode` in interface `Watch`
  Overrides:
    `notifySelectedLeafNode` in class `AbstractWatch`
  Parameters:
    `node` - the node that was matched.
    `locationId` -
  Throws:
    `XPathException`

### endSelectedParentNode

    public void endSelectedParentNode(int 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 element
  Throws:
    `ValidationException` - May be raised if the constraint implemented by this Watch is violated @param locationId
    `XPathException` - May be raised if a constraint implemented by this Watch is violated

Copyright (c) 2004-2010 Saxonica Limited. All rights reserved.