net.esper.view.std
Class LastElementView

java.lang.Object
  extended by net.esper.view.ViewSupport
      extended by net.esper.view.std.LastElementView
All Implemented Interfaces:
Iterable<EventBean>, CloneableView, EventCollection, View, Viewable

public class LastElementView
extends ViewSupport
implements CloneableView

This view is a very simple view presenting the last event posted by the parent view to any subviews. Only the very last event object is kept by this view. The update method invoked by the parent view supplies new data in an object array, of which the view keeps the very last instance as the 'last' or newest event. The view always has the same schema as the parent view and attaches to anything, and accepts no parameters. Useful is the last view for example for "stocks.time_window(100).last()". Notice that "stocks.last().size()" and "stocks.win:length(10).std:lastevent().std:size()" must always return 0 or 1. Thus if 5 pieces of new data arrive, the child view receives 5 elements of new data and also 4 pieces of old data which is the first 4 elements of new data. I.e. New data elements immediatly gets to be old data elements. Old data received from parent is not handled, it is ignored. We thus post old data as follows: last event is not null + new data from index zero to N-1, where N is the index of the last element in new data


Field Summary
protected  EventBean lastEvent
          The last new element posted from a parent view.
 
Fields inherited from class net.esper.view.ViewSupport
parent
 
Constructor Summary
LastElementView()
           
 
Method Summary
 View cloneView(ViewServiceContext context)
           
 EventType getEventType()
          Provides metadata information about the type of object the event collection contains.
 Iterator<EventBean> iterator()
          Allows iteration through all elements in this event collection.
 String toString()
           
 void update(EventBean[] newData, EventBean[] oldData)
          Notify that data has been added or removed from the Viewable parent.
 
Methods inherited from class net.esper.view.ViewSupport
addView, dumpChildViews, dumpUpdateParams, findDescendent, getParent, getViews, hasViews, removeView, setParent, updateChildren, updateChildren
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

lastEvent

protected EventBean lastEvent
The last new element posted from a parent view.

Constructor Detail

LastElementView

public LastElementView()
Method Detail

cloneView

public View cloneView(ViewServiceContext context)
Specified by:
cloneView in interface CloneableView

getEventType

public final EventType getEventType()
Description copied from interface: EventCollection
Provides metadata information about the type of object the event collection contains.

Specified by:
getEventType in interface EventCollection
Returns:
metadata for the objects in the collection

update

public void update(EventBean[] newData,
                   EventBean[] oldData)
Description copied from interface: View
Notify that data has been added or removed from the Viewable parent. The last object in the newData array of objects would be the newest object added to the parent view. The first object of the oldData array of objects would be the oldest object removed from the parent view. If the call to update contains new (inserted) data, then the first argument will be a non-empty list and the second will be empty. Similarly, if the call is a notification of deleted data, then the first argument will be empty and the second will be non-empty. Either the newData or oldData will be non-null. This method won't be called with both arguments being null, but either one could be null. The same is true for zero-length arrays. Either newData or oldData will be non-empty. If both are non-empty, then the update is a modification notification. When update() is called on a view by the parent object, the data in newData will be in the collection of the parent, and its data structures will be arranged to reflect that. The data in oldData will not be in the parent's data structures, and any access to the parent will indicate that that data is no longer there.

Specified by:
update in interface View
Parameters:
newData - is the new data that has been added to the parent view
oldData - is the old data that has been removed from the parent view

iterator

public final Iterator<EventBean> iterator()
Description copied from interface: EventCollection
Allows iteration through all elements in this event collection. The iterator will return the elements in the collection in their natural order, or, if there is no natural ordering, in some unpredictable order.

Specified by:
iterator in interface Iterable<EventBean>
Specified by:
iterator in interface EventCollection
Returns:
an iterator which will go through all current elements in the collection.

toString

public final String toString()
Overrides:
toString in class Object