com.espertech.esper.view.std

Class GroupByViewImpl

java.lang.Object

com.espertech.esper.view.ViewSupport

com.espertech.esper.view.std.GroupByViewImpl

All Implemented Interfaces:

EventCollection, GroupByView, View, Viewable, ViewDataVisitableContainer, java.lang.Iterable<EventBean>

public class GroupByViewImpl
extends ViewSupport
implements GroupByView

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 Summary

Fields

Modifier and Type	Field and Description
protected AgentInstanceViewFactoryChainContext	agentInstanceContext
protected java.util.Map<java.lang.Object,View>	subViewPerKey
static java.lang.String	VIEWNAME

Fields inherited from class com.espertech.esper.view.ViewSupport

EMPTY_VIEW_ARRAY, parent

Constructor Summary

Constructors

Constructor and Description
GroupByViewImpl(GroupByViewFactory groupByViewFactory, AgentInstanceViewFactoryChainContext agentInstanceContext) Constructor.

Method Summary

Modifier and Type	Method and Description
protected static java.lang.Object	addUpgradeToDequeIfPopulated(java.lang.Object holder, EventBean theEvent)
protected static EventBean[]	convertToArray(java.lang.Object eventOrDeque)
EventType	getEventType() Provides metadata information about the type of object the event collection contains.
GroupByViewFactory	getViewFactory()
java.util.Iterator<EventBean>	iterator() Allows iteration through all elements in this event collection.
boolean	removeView(View view) Remove a view.
java.lang.String	toString()
void	update(EventBean[] newData, EventBean[] oldData) Notify that data has been added or removed from the Viewable parent.
static void	visitView(ViewDataVisitorContained viewDataVisitor, java.lang.Object groupkey, View view)
void	visitViewContainer(ViewDataVisitorContained viewDataVisitor)

Methods inherited from class com.espertech.esper.view.ViewSupport

addView, addView, dumpChildViews, dumpUpdateParams, dumpUpdateParams, findDescendent, findViewIndex, getParent, getViews, hasViews, removeAllViews, removeView, setParent, updateChildren, updateChildren

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface com.espertech.esper.view.View

getParent, setParent

Methods inherited from interface com.espertech.esper.view.Viewable

addView, getViews, hasViews, removeAllViews

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Detail

VIEWNAME

public static final java.lang.String VIEWNAME

See Also:

Constant Field Values

agentInstanceContext

protected final AgentInstanceViewFactoryChainContext agentInstanceContext

subViewPerKey

protected final java.util.Map<java.lang.Object,View> subViewPerKey

Constructor Detail

GroupByViewImpl

public GroupByViewImpl(GroupByViewFactory groupByViewFactory,
                       AgentInstanceViewFactoryChainContext agentInstanceContext)

Constructor.

Parameters:

groupByViewFactory - view factory

agentInstanceContext - contains required view services

Method Detail

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

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 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.

Specified by:

iterator in interface EventCollection

Specified by:

iterator in interface java.lang.Iterable<EventBean>

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

visitViewContainer

public void visitViewContainer(ViewDataVisitorContained viewDataVisitor)

Specified by:

visitViewContainer in interface ViewDataVisitableContainer

visitView

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

removeView

public boolean removeView(View view)

Description copied from interface: Viewable

Remove a view.

Specified by:

removeView in interface Viewable

Overrides:

removeView in class ViewSupport

Parameters:

view - to remove

Returns:

true to indicate that the view to be removed existed within this view, false if the view to remove could not be found

addUpgradeToDequeIfPopulated

protected static java.lang.Object addUpgradeToDequeIfPopulated(java.lang.Object holder,
                                                               EventBean theEvent)

convertToArray

protected static EventBean[] convertToArray(java.lang.Object eventOrDeque)