com.espertech.esper.view.std

Class FirstUniqueByPropertyView

java.lang.Object

com.espertech.esper.view.ViewSupport

com.espertech.esper.view.std.FirstUniqueByPropertyView

All Implemented Interfaces:

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

public class FirstUniqueByPropertyView
extends ViewSupport
implements DataWindowView

This view retains the first event for each multi-key of distinct property values.

The view does not post a remove stream unless explicitly deleted from.

The view swallows any insert stream events that provide no new distinct set of property values.

Field Summary

Fields

Modifier and Type	Field and Description
protected AgentInstanceViewFactoryChainContext	agentInstanceViewFactoryContext
protected java.util.Map<java.lang.Object,EventBean>	firstEvents

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

EMPTY_VIEW_ARRAY, parent

Constructor Summary

Constructors

Constructor and Description
FirstUniqueByPropertyView(FirstUniqueByPropertyViewFactory viewFactory, AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)

Method Summary

Modifier and Type	Method and Description
EventType	getEventType() Provides metadata information about the type of object the event collection contains.
ExprNode[]	getUniqueCriteria() Returns the expressions supplying the unique value to keep the most recent record for.
protected java.lang.Object	getUniqueKey(EventBean theEvent)
ViewFactory	getViewFactory()
void	internalHandleAdded(java.lang.Object key, EventBean newEvent)
void	internalHandleRemoved(java.lang.Object key, EventBean lastValue)
boolean	isEmpty() Returns true if 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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Detail

firstEvents

protected final java.util.Map<java.lang.Object,EventBean> firstEvents

agentInstanceViewFactoryContext

protected final AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext

Constructor Detail

FirstUniqueByPropertyView

public FirstUniqueByPropertyView(FirstUniqueByPropertyViewFactory viewFactory,
                                 AgentInstanceViewFactoryChainContext agentInstanceViewFactoryContext)

Method Detail

getUniqueCriteria

public final ExprNode[] getUniqueCriteria()

Returns the expressions supplying the unique value to keep the most recent record for.

Returns:

expressions for unique value

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

internalHandleRemoved

public void internalHandleRemoved(java.lang.Object key,
                                  EventBean lastValue)

internalHandleAdded

public void internalHandleAdded(java.lang.Object key,
                                EventBean newEvent)

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

getUniqueKey

protected java.lang.Object getUniqueKey(EventBean theEvent)

isEmpty

public boolean isEmpty()

Returns true if empty.

Returns:

true if empty

visitView

public void visitView(ViewDataVisitor viewDataVisitor)

Specified by:

visitView in interface ViewDataVisitable

getViewFactory

public ViewFactory getViewFactory()

Specified by:

getViewFactory in interface GroupableView