com.dxfeed.model

Class TimeSeriesEventModel<E extends TimeSeriesEvent<?>>

java.lang.Object

com.dxfeed.model.AbstractIndexedEventModel<E,AbstractIndexedEventModel.Entry<E>>

com.dxfeed.model.IndexedEventModel<E>

com.dxfeed.model.TimeSeriesEventModel<E>

Type Parameters:

E - the type of events.

All Implemented Interfaces:

AutoCloseable

public class TimeSeriesEventModel<E extends TimeSeriesEvent<?>>
extends IndexedEventModel<E>

Model for a list of time-series events. This class handles all snapshot and transaction logic of TimeSeriesEvent class and arranges incoming events into a list ordered by their time.

The model must be configured with symbol and fromTime to subscribe and attached to a DXFeed instance to start operation.

The view of the current list of events is available via getEventsList method. Model change notifications are provided via addListener method of this list. It accepts an instance of ObservableListModelListener class.

Users of this model only see the list of events in a consistent state. This model delays incoming events which are part of incomplete snapshot or ongoing transaction until snapshot is complete or transaction has ended. These pending events cannot be seen neither via list nor via listener calls, and so eventFlags of events in the model are set to zero. The eventFlags are only used and must be taken into account when processing time-series events directly via low-level DXFeedSubscription or DXFeedTimeSeriesSubscription classes.

Sample usage

dxFeed API comes with a set of samples. DXFeedCandleChart sample is a very simple UI application that shows how to use this model with Candle event to paint a simple candle chart, concentrating your effort on data representation (painting) logic, while delegating all the data-handling logic to this model.

Resource management and closed models

Attached model is a potential memory leak. If the pointer to attached model is lost, then there is no way to detach this model from the feed and the model will not be reclaimed by the garbage collector as long as the corresponding feed is still used. Detached model can be reclaimed by the garbage collector, but detaching model requires knowing the pointer to the feed at the place of the call, which is not always convenient.

The convenient way to detach model from the feed is to call its close method. Closed model becomes permanently detached from all feeds, removes all its listeners and is guaranteed to be reclaimable by the garbage collector as soon as all external references to it are cleared.

Threads and locks

This class is not tread-safe and requires external synchronization. The only thread-safe methods are attach, detach and close.

You must query the state of attached model only from inside of the notification invocations or from within the thread that performs those notifications.

Installed ObservableListModelListener instances are invoked from a separate thread via the executor. Default executor for all models is configured with DXEndpoint.executor method. Each model can individually override its executor with setExecutor method. The corresponding modelChanged notification is guaranteed to never be concurrent, even though it may happen from different threads if executor is multi-threaded.

In practice, it means that is UI applications you must install UI-thread-bound execution to your DXEndpoint via DXEndpoint.executor method, so that you can freely use all methods of this model from UI thread.

Custom executor can be used by backend applications that do not need to immediately update this model on arrival of new events, but want to update the model at a later time, for example, from inside of a servlet request. This approach is explained with code samples in Threads and locks section of DXFeedSubscription class documentation.

Nested Class Summary

Nested classes/interfaces inherited from class com.dxfeed.model.AbstractIndexedEventModel

AbstractIndexedEventModel.Entry<V>

Constructor Summary

Constructors

Constructor and Description
TimeSeriesEventModel(Class<? extends E> eventType) Creates new model.

Method Summary

Modifier and Type	Method and Description
void	clear() Clears subscription symbol and sets fromTime to Long.MAX_VALUE, subsequently, all events in this model are cleared.
long	getFromTime() Returns the time from which to subscribe for time-series, or Long.MAX_VALUE is not subscribed (this is a default value).
Object	getSymbol() Returns model subscription symbol, or null is not subscribed (this is a default value).
void	setFromTime(long fromTime) Changes the time from which to subscribe for time-series, use Long.MAX_VALUE to unsubscribe.
void	setSymbol(Object symbol) Changes symbol for this model to subscribe for.

Methods inherited from class com.dxfeed.model.IndexedEventModel

close, createEntry, getEventsList, modelChanged

Methods inherited from class com.dxfeed.model.AbstractIndexedEventModel

attach, detach, entryListIterator, get, getExecutor, getSizeLimit, isClosed, isSnapshotEnd, listIterator, listIterator, setExecutor, setSizeLimit, size

Methods inherited from class java.lang.Object

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

Constructor Detail

TimeSeriesEventModel

public TimeSeriesEventModel(Class<? extends E> eventType)

Creates new model. This model is not attached to any feed, not subscribed to any symbol. Use setSymbol(java.lang.Object) to specify subscription symbol, setFromTime(long) to specify subscription time, and AbstractIndexedEventModel.attach(com.dxfeed.api.DXFeed) method to specify feed to start receiving events.

Parameters:

eventType - the event type.

Throws:

NullPointerException - if event type is null.

Method Detail

clear

public void clear()

Clears subscription symbol and sets fromTime to Long.MAX_VALUE, subsequently, all events in this model are cleared.

Overrides:

clear in class AbstractIndexedEventModel<E extends TimeSeriesEvent<?>,AbstractIndexedEventModel.Entry<E extends TimeSeriesEvent<?>>>

getSymbol

public Object getSymbol()

Returns model subscription symbol, or null is not subscribed (this is a default value).

Overrides:

getSymbol in class AbstractIndexedEventModel<E extends TimeSeriesEvent<?>,AbstractIndexedEventModel.Entry<E extends TimeSeriesEvent<?>>>

Returns:

model subscription symbol.

setSymbol

public void setSymbol(Object symbol)

Changes symbol for this model to subscribe for.

Overrides:

setSymbol in class AbstractIndexedEventModel<E extends TimeSeriesEvent<?>,AbstractIndexedEventModel.Entry<E extends TimeSeriesEvent<?>>>

Parameters:

symbol - model subscription symbol, use null to unsubscribe.

getFromTime

public long getFromTime()

Returns the time from which to subscribe for time-series, or Long.MAX_VALUE is not subscribed (this is a default value).

Returns:

the time from which to subscribe for time-series.

setFromTime

public void setFromTime(long fromTime)

Changes the time from which to subscribe for time-series, use Long.MAX_VALUE to unsubscribe.

Parameters:

fromTime - the time from which to subscribe for time-series, use Long.MAX_VALUE to unsubscribe.