com.espertech.esper.view.window
Class ExternallyTimedWindowView

java.lang.Object
  com.espertech.esper.view.ViewSupport
      com.espertech.esper.view.window.ExternallyTimedWindowView

All Implemented Interfaces:

CloneableView, DataWindowView, EventCollection, GroupableView, View, Viewable, ViewDataVisitable, java.lang.Iterable<EventBean>

public class ExternallyTimedWindowView
extends ViewSupport
implements DataWindowView, CloneableView

View for a moving window extending the specified amount of time into the past, driven entirely by external timing supplied within long-type timestamp values in a field of the event beans that the view receives. The view is completely driven by timestamp values that are supplied by the events it receives, and does not use the schedule service time. It requires a field name as parameter for a field that returns ascending long-type timestamp values. It also requires a long-type parameter setting the time length in milliseconds of the time window. Events are expected to provide long-type timestamp values in natural order. The view does itself not use the current system time for keeping track of the time window, but just the timestamp values supplied by the events sent in. The arrival of new events with a newer timestamp then past events causes the window to be re-evaluated and the oldest events pushed out of the window. Ie. Assume event X1 with timestamp T1 is in the window. When event Xn with timestamp Tn arrives, and the window time length in milliseconds is t, then if ((Tn - T1) > t == true) then event X1 is pushed as oldData out of the window. It is assumed that events are sent in in their natural order and the timestamp values are ascending.

Field Summary

protected AgentInstanceViewFactoryChainContext	agentInstanceViewFactoryContext
protected TimeWindow	timeWindow

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

EMPTY_VIEW_ARRAY, parent

Constructor Summary

ExternallyTimedWindowView(ExternallyTimedWindowViewFactory externallyTimedWindowViewFactory, ExprNode timestampExpression, ExprEvaluator timestampExpressionEval, ExprTimePeriodEvalDeltaConst timeDeltaComputation, ViewUpdatedCollection viewUpdatedCollection, AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)
Constructor.

Method Summary

View	cloneView() Duplicates the view.
EventType	getEventType() Provides metadata information about the type of object the event collection contains.
ExprTimePeriodEvalDeltaConst	getTimeDeltaComputation()
ExprNode	getTimestampExpression() Returns the field name to get timestamp values from.
ViewFactory	getViewFactory()
ViewUpdatedCollection	getViewUpdatedCollection()
boolean	isEmpty() Returns true to indicate the window is empty, or false if the view is not empty.
java.util.Iterator<EventBean>	iterator() Allows iteration through all elements in this event collection.
java.lang.String	toString()
void	update(EventBean[] newData, EventBean[] oldData) Notify that data has been added or removed from the Viewable parent.
void	visitView(ViewDataVisitor viewDataVisitor)

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

Field Detail

timeWindow

protected final TimeWindow timeWindow

agentInstanceViewFactoryContext

protected AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext

Constructor Detail

ExternallyTimedWindowView

public ExternallyTimedWindowView(ExternallyTimedWindowViewFactory externallyTimedWindowViewFactory,
                                 ExprNode timestampExpression,
                                 ExprEvaluator timestampExpressionEval,
                                 ExprTimePeriodEvalDeltaConst timeDeltaComputation,
                                 ViewUpdatedCollection viewUpdatedCollection,
                                 AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)

Constructor.

Parameters:

timestampExpression - is the field name containing a long timestamp value that should be in ascending order for the natural order of events and is intended to reflect System.currentTimeInMillis but does not necessarily have to. out of the window as oldData in the update method. The view compares each events timestamp against the newest event timestamp and those with a delta greater then secondsBeforeExpiry are pushed out of the window.

viewUpdatedCollection - is a collection that the view must update when receiving events

externallyTimedWindowViewFactory - for copying this view in a group-by

agentInstanceViewFactoryContext - context for expression evalauation

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

getTimestampExpression

public final ExprNode getTimestampExpression()

Returns the field name to get timestamp values from.

Returns:

field name for timestamp values

getTimeDeltaComputation

public ExprTimePeriodEvalDeltaConst getTimeDeltaComputation()

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

visitView

public void visitView(ViewDataVisitor viewDataVisitor)

Specified by:

visitView in interface ViewDataVisitable

isEmpty

public boolean isEmpty()

Returns true to indicate the window is empty, or false if the view is not empty.

Returns:

true if empty

getViewUpdatedCollection

public ViewUpdatedCollection getViewUpdatedCollection()

getViewFactory

public ViewFactory getViewFactory()

Specified by:

getViewFactory in interface GroupableView