Package com.espertech.esper.common.internal.view.unique

Class UniqueByPropertyView

java.lang.Object
com.espertech.esper.common.internal.view.core.ViewSupport
com.espertech.esper.common.internal.view.unique.UniqueByPropertyView
All Implemented Interfaces:
DataWindowView, View, Viewable, ViewDataVisitable, Iterable<EventBean>
public class UniqueByPropertyView extends ViewSupport implements DataWindowView
This view includes only the most recent among events having the same value for the specified field or fields. 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 Details

  • Constructor Details

  • Method Details

    • getEventType

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

      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

    • isEmpty

      public boolean isEmpty()
      Returns true if the view is empty.
      Returns:
      true if empty

    • iterator

      public final Iterator<EventBean> iterator()
      Description copied from interface: Viewable
      Allows iteration through all elements in this viewable. 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 Viewable
      Returns:
      an iterator which will go through all current elements in the collection.

    • toString

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

    • getUniqueKey

      protected Object getUniqueKey(EventBean theEvent)

    • visitView

      public void visitView(ViewDataVisitor viewDataVisitor)
      Specified by:
      visitView in interface ViewDataVisitable

    • getViewFactory

      public ViewFactory getViewFactory()