com.espertech.esper.view.std
Class GroupByViewImpl

java.lang.Object
  com.espertech.esper.view.ViewSupport
      com.espertech.esper.view.std.GroupByViewImpl

All Implemented Interfaces:

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

public class GroupByViewImpl
extends ViewSupport
implements CloneableView, 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

protected AgentInstanceViewFactoryChainContext	agentInstanceContext
protected java.lang.String[]	propertyNames
protected java.util.Map<java.lang.Object,java.lang.Object>	subViewsPerKey
static java.lang.String	VIEWNAME

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

EMPTY_VIEW_ARRAY, parent

Constructor Summary

GroupByViewImpl(AgentInstanceViewFactoryChainContext agentInstanceContext, ExprNode[] criteriaExpressions, ExprEvaluator[] criteriaEvaluators)
Constructor.

Method Summary

protected static java.lang.Object	addUpgradeToDequeIfPopulated(java.lang.Object holder, EventBean theEvent)
View	cloneView() Duplicates the view.
protected static EventBean[]	convertToArray(java.lang.Object eventOrDeque)
ExprNode[]	getCriteriaExpressions() Returns the field name that provides the key valie by which to group by.
EventType	getEventType() Provides metadata information about the type of object the event collection contains.
java.util.Iterator<EventBean>	iterator() Allows iteration through all elements in this event collection.
static java.lang.Object	makeSubViews(GroupByView groupView, java.lang.String[] propertyNames, java.lang.Object groupByValues, AgentInstanceViewFactoryChainContext agentInstanceContext) Instantiate subviews for the given group view and the given key value to group-by.
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.
protected static void	updateChildViews(java.lang.Object subViews, EventBean[] newData, EventBean[] oldData)
static void	visitView(ViewDataVisitorContained viewDataVisitor, java.lang.Object groupkey, java.lang.Object subviewHolder)
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

Field Detail

VIEWNAME

public static final java.lang.String VIEWNAME

See Also:

Constant Field Values

agentInstanceContext

protected final AgentInstanceViewFactoryChainContext agentInstanceContext

propertyNames

protected java.lang.String[] propertyNames

subViewsPerKey

protected final java.util.Map<java.lang.Object,java.lang.Object> subViewsPerKey

Constructor Detail

GroupByViewImpl

public GroupByViewImpl(AgentInstanceViewFactoryChainContext agentInstanceContext,
                       ExprNode[] criteriaExpressions,
                       ExprEvaluator[] criteriaEvaluators)

Constructor.

Parameters:

criteriaExpressions - is the fields from which to pull the values to group by

agentInstanceContext - contains required view services

Method Detail

cloneView

public View cloneView()

Description copied from interface: CloneableView

Duplicates the view.

Expected to return a same view in initialized state for grouping.

Specified by:

cloneView in interface CloneableView

getCriteriaExpressions

public ExprNode[] getCriteriaExpressions()

Returns the field name that provides the key valie by which to group by.

Specified by:

getCriteriaExpressions in interface GroupByView

Returns:

field name providing group-by key.

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

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

makeSubViews

public static java.lang.Object makeSubViews(GroupByView groupView,
                                            java.lang.String[] propertyNames,
                                            java.lang.Object groupByValues,
                                            AgentInstanceViewFactoryChainContext agentInstanceContext)

Instantiate subviews for the given group view and the given key value to group-by. Makes shallow copies of each child view and its subviews up to the merge point. Sets up merge data views for merging the group-by key value back in.

Parameters:

groupView - is the parent view for which to copy subviews for

groupByValues - is the key values to group-by

agentInstanceContext - is the view services that sub-views may need

propertyNames - names of expressions or properties

Returns:

a single view or a list of views that are copies of the original list, with copied children, with data merge views added to the copied child leaf views.

visitViewContainer

public void visitViewContainer(ViewDataVisitorContained viewDataVisitor)

Specified by:

visitViewContainer in interface ViewDataVisitableContainer

visitView

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

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

updateChildViews

protected static void updateChildViews(java.lang.Object subViews,
                                       EventBean[] newData,
                                       EventBean[] oldData)

addUpgradeToDequeIfPopulated

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

convertToArray

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