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

Class GroupByViewImpl

java.lang.Object
com.espertech.esper.common.internal.view.core.ViewSupport
com.espertech.esper.common.internal.view.groupwin.GroupByViewImpl
All Implemented Interfaces:
AgentInstanceMgmtCallback, View, Viewable, ViewDataVisitableContainer, GroupByView, Iterable<EventBean>
public class GroupByViewImpl extends ViewSupport implements GroupByView, AgentInstanceMgmtCallback
The group view splits the data in a stream to multiple subviews, based on a key index. The key is one or more fields in the stream. Any view that follows the GROUP view will be executed separately on each subview, one per unique key.

The view takes a single parameter which is the field name returning the key value to group.

This view can, for example, be used to calculate the average price per symbol for a list of symbols.

The view treats its child views and their child views as prototypes. It dynamically instantiates copies of each child view and their child views, and the child view's child views as so on. When there are no more child views or the special merge view is encountered, it ends. The view installs a special merge view unto each leaf child view that merges the value key that was grouped by back into the stream using the group-by field name.

  • 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

    • getViewFactory

      public GroupByViewFactory getViewFactory()
      Specified by:
      getViewFactory in interface GroupByView

    • 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

    • 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

    • visitViewContainer

      public void visitViewContainer(ViewDataVisitorContained viewDataVisitor)
      Specified by:
      visitViewContainer in interface ViewDataVisitableContainer

    • visitView

      public static void visitView(ViewDataVisitorContained viewDataVisitor, Object groupkey, View view)

    • getMergeView

      public MergeView getMergeView()
      Specified by:
      getMergeView in interface GroupByView

    • getAgentInstanceContext

      public AgentInstanceViewFactoryChainContext getAgentInstanceContext()
      Specified by:
      getAgentInstanceContext in interface GroupByView

    • stop

      public void stop(AgentInstanceStopServices services)
      Specified by:
      stop in interface AgentInstanceMgmtCallback

    • addUpgradeToDequeIfPopulated

      protected static Object addUpgradeToDequeIfPopulated(Object holder, EventBean theEvent)

    • convertToArray

      protected static EventBean[] convertToArray(Object eventOrDeque)