net.esper.view.std
Class UniqueByPropertyView

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

public final class UniqueByPropertyView
extends ViewSupport

This view includes only the most recent among events having the same value for the specified field. The view accepts the field name as parameter from which the unique values are obtained. For example, a trade's symbol could be used as a unique value. In this example, the first trade for symbol IBM would be posted as new data to child views. When the second trade for symbol IBM arrives the second trade is posted as new data to child views, and the first trade is posted as old data. Should more than one trades for symbol IBM arrive at the same time (like when batched) then the child view will get all new events in newData and all new events in oldData minus the most recent event. When the current new event arrives as old data, the the current unique event gets thrown away and posted as old data to child views. Iteration through the views data shows only the most recent events received for the unique value in the order that events arrived in. The type of the field returning the unique value can be any type but should override equals and hashCode() as the type plays the role of a key in a map storing unique values.


Field Summary
 
Fields inherited from class net.esper.view.ViewSupport
parent
 
Constructor Summary
UniqueByPropertyView()
          Default constructor - required by all views to adhere to the Java bean specification.
UniqueByPropertyView(java.lang.String uniqueFieldName)
          Constructor.
 
Method Summary
 java.lang.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.
 java.lang.String getUniqueFieldName()
          Returns the name of the field supplying the unique value to keep the most recent record for.
 java.util.Iterator<EventBean> iterator()
          Allows iteration through all elements in this event collection.
 void setParent(Viewable parent)
          Called when the View is added to a Viewable object.
 void setUniqueFieldName(java.lang.String uniqueFieldName)
          Sets the name of the field supplying the unique value to keep the most recent record for.
 java.lang.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, shallowCopyView, updateChildren, updateChildren
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

UniqueByPropertyView

public UniqueByPropertyView()
Default constructor - required by all views to adhere to the Java bean specification.


UniqueByPropertyView

public UniqueByPropertyView(java.lang.String uniqueFieldName)
Constructor.

Parameters:
uniqueFieldName - is the field from which to pull the unique value
Method Detail

setParent

public void setParent(Viewable parent)
Description copied from interface: View
Called when the View is added to a Viewable object.

Specified by:
setParent in interface View
Overrides:
setParent in class ViewSupport
Parameters:
parent - is the parent that this view is a child of

getUniqueFieldName

public final java.lang.String getUniqueFieldName()
Returns the name of the field supplying the unique value to keep the most recent record for.

Returns:
field name for unique value

setUniqueFieldName

public final void setUniqueFieldName(java.lang.String uniqueFieldName)
Sets the name of the field supplying the unique value to keep the most recent record for.

Parameters:
uniqueFieldName - field name for unique value

attachesTo

public final java.lang.String attachesTo(Viewable parentView)
Description copied from interface: View
Return null if the view will accept being attached to a particular object.

Parameters:
parentView - is the potential parent for this view
Returns:
null if this view can successfully attach to the parent, an error message if it cannot.

getEventType

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

Returns:
metadata for the objects in the collection

update

public final 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.

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 java.util.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.

Returns:
an iterator which will go through all current elements in the collection.

toString

public final java.lang.String toString()
Overrides:
toString in class java.lang.Object