com.espertech.esper.view.std
Class MergeView

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

All Implemented Interfaces:

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

public final class MergeView
extends ViewSupport
implements CloneableView, MergeViewMarker

The merge view works together with a group view that splits the data in a stream to multiple subviews, based on a key index. Every group view requires a merge view to merge the many subviews back into a single view. Typically the last view in a chain containing a group view is a merge view. The merge view has no other responsibility then becoming the single last instance in the chain to which external listeners for updates can be attached to receive updates for the many subviews that have this merge view as common child views. The parent view of this view is generally the AddPropertyValueView that adds the grouped-by information back into the data.

Field Summary

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

EMPTY_VIEW_ARRAY, parent

Constructor Summary

MergeView(AgentInstanceViewFactoryChainContext agentInstanceContext, ExprNode[] groupCriteria, EventType resultEventType, boolean removable)
Constructor.

Method Summary

void	addParentView(AddPropertyValueView parentView) Add a parent data merge view.
View	cloneView() Duplicates the view.
EventType	getEventType() Provides metadata information about the type of object the event collection contains.
ExprNode[]	getGroupFieldNames() Returns the field name that contains the values to group by.
java.util.Iterator<EventBean>	iterator() Allows iteration through all elements in this event collection.
void	removeParentView(View view)
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 com.espertech.esper.view.ViewSupport

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

Constructor Detail

MergeView

public MergeView(AgentInstanceViewFactoryChainContext agentInstanceContext,
                 ExprNode[] groupCriteria,
                 EventType resultEventType,
                 boolean removable)

Constructor.

Parameters:

groupCriteria - is the fields from which to pull the value to group by

resultEventType - is passed by the factory as the factory adds the merged fields to an event type

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

getGroupFieldNames

public final ExprNode[] getGroupFieldNames()

Returns the field name that contains the values to group by.

Specified by:

getGroupFieldNames in interface MergeViewMarker

Returns:

field name providing group key value

addParentView

public final void addParentView(AddPropertyValueView parentView)

Add a parent data merge view.

Specified by:

addParentView in interface MergeViewMarker

Parameters:

parentView - is the parent data merge view to add

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

removeParentView

public void removeParentView(View view)