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java.lang.Objectnet.esper.view.ViewSupport
net.esper.view.std.LastElementView
public class LastElementView
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 | |
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protected EventBean |
lastEvent
The last new element posted from a parent view. |
Fields inherited from class net.esper.view.ViewSupport |
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parent |
Constructor Summary | |
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LastElementView()
Constructor. |
Method Summary | |
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String |
attachesTo(Viewable parentView)
Return null if the view will accept being attached to a particular object. |
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()
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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 |
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addView, dumpChildViews, dumpUpdateParams, findDescendent, getParent, getViews, hasViews, removeView, setParent, shallowCopyView, updateChildren, updateChildren |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait |
Field Detail |
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protected EventBean lastEvent
Constructor Detail |
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public LastElementView()
Method Detail |
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public final String attachesTo(Viewable parentView)
View
parentView
- is the potential parent for this view
public final EventType getEventType()
EventCollection
public void update(EventBean[] newData, EventBean[] oldData)
View
newData
- is the new data that has been added to the parent viewoldData
- is the old data that has been removed from the parent viewpublic final Iterator<EventBean> iterator()
EventCollection
public final String toString()
toString
in class Object
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