OnDemandService (dxFeed API 3.320)

java.lang.Object
- com.dxfeed.ondemand.OnDemandService

```
public abstract class OnDemandService
extends Object
```
Provides on-demand historical tick data replay controls. This class is used to seamlessly transition from ordinary real-time or delayed data feed to the replay of the tick-by-tick history of market data behaviour without any changes to the code that consumes and process these market events.
As single OnDemandService instance is conceptually associated with each DXEndpoint endpoint instance with the role of FEED or ON_DEMAND_FEED. You can retrieve OnDemandService instance that is associated with a given DXEndpoint using getInstance(endpoint) method.
For example, OnDemandService instance for a default DXFeed that is featured in the documentation of DXFeed class and is retrieved via DXFeed.getInstance() method can be acquired with the following code:
```
 DXEndpoint endpoint = DXEndpoint.getInstance();
 OnDemandService onDemand = getInstance(endpoint);
```
This instance can be used for on-demand historical tick data replay only when endpoint is connected to the on-demand data provider and the appropriate credentials are provided. isReplaySupported returns true when it is so.
On-demand replay is started with replay method that takes time as a parameters. DXFeed is then disconnected from other data providers, pre-buffers historical tick data for replay, and starts replay of the data as if it was coming from the data feeds now. All the usual APIs that are part of DXFeed like subscription and various models can be used normally as with the ordinary real-time or delayed data feed.
Replay speed can be changed on the fly with setSpeed method or it can be set initially when starting replay with a two-argument version of replay method. pause() method is the same as setSpeed(0).
stopAndResume method stops data replay and resumes ordinary real-time or delayed data feed that was used before replay method was invoked. Endpoints with a role of ON_DEMAND_FEED do not have an ordinary feed (they are essentially on-demand only) and thus stopAndResume method works like stopAndClear for them.
State and change notifications
On-demand historical tick data replay state can be queried with isReplaySupported, isReplay, getSpeed, and getTime methods. The changes in those values can be tracked by installing PropertyChangeListener with addPropertyChangeListener method. All change notifications happen using executor that is configured for the corresponding DXEndpoint with DXEndpoint.executor(...) method.
Threads and locks
This class is thread-safe and can be used concurrently from multiple threads without external synchronization.
Implementation details

Implementation of this class is available only when the optional "dxfeed-ondemand.jar" is in the class-path.

Constructor Summary

Constructors
Modifier Constructor and Description

protected OnDemandService()
Protected constructor for implementations of OnDemandService.

Constructors
Modifier	Constructor and Description
`protected`	`OnDemandService()` Protected constructor for implementations of `OnDemandService`.

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`abstract void`	`addPropertyChangeListener(PropertyChangeListener listener)` Adds listener that is notified about changes in on-demand service properties.
`abstract DXEndpoint`	`getEndpoint()` Returns `DXEndpoint` that is associated with this on-demand service.
`static OnDemandService`	`getInstance()` Returns on-demand service for the default `DXEndpoint` instance with `ON_DEMAND_FEED` role that is not connected to any other real-time or delayed data feed.
`static OnDemandService`	`getInstance(DXEndpoint endpoint)` Returns on-demand service for the specified `DXEndpoint`.
`abstract double`	`getSpeed()` Returns on-demand historical data replay speed.
`abstract Date`	`getTime()` Returns current or last on-demand historical data replay time.
`protected abstract void`	`initImpl(DXEndpoint endpoint)` Protected initialization method to bind `OnDemandService` instance to `DXEndpoint` instance.
`abstract boolean`	`isClear()` Returns true when this on-demand historical data replay service is in clear mode.
`abstract boolean`	`isReplay()` Returns true when this on-demand historical data replay service is in replay mode.
`abstract boolean`	`isReplaySupported()` Returns `true` when on-demand historical data replay mode is supported.
`abstract void`	`pause()` Pauses on-demand historical data replay and keeps data snapshot.
`abstract void`	`removePropertyChangeListener(PropertyChangeListener listener)` Removes listener that is notified about changes in on-demand service properties.
`void`	`replay(Date time)` Turns on-demand historical data replay mode from a specified time with real-time speed.
`abstract void`	`replay(Date time, double speed)` Turns on-demand historical data replay mode from a specified time and with a specified speed.
`abstract void`	`setSpeed(double speed)` Changes on-demand historical data replay speed while continuing replay at current `getTime()` time}.
`abstract void`	`stopAndClear()` Stops incoming data and clears it without resuming data updates.
`abstract void`	`stopAndResume()` Stops on-demand historical data replay and resumes ordinary data feed.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - OnDemandService
```
protected OnDemandService()
```
    Protected constructor for implementations of OnDemandService.
- Method Detail
  - getInstance
```
public static OnDemandService getInstance()
```
    Returns on-demand service for the default DXEndpoint instance with ON_DEMAND_FEED role that is not connected to any other real-time or delayed data feed. This method is a shortcut for:
```
 OnDemandService.getInstance(DXEndpoint.getInstance(ON_DEMAND_FEED))
```
    If you need an instance of OnDemandService to seamlessly switch from other real-time or delayed data feed to on-demand historical tick data replay, then use getInstance(endpoint) method for a specific endpoint that you are using.
    This method works only when the optional "dxfeed-ondemand.jar" is in the class-path.
    Returns:
    
    on-demand endpoint for the default DXEndpoint instance.
    
    Throws:
    
    UnsupportedOperationException - if "dxfeed-ondemand.jar" is not in the class-path.
  - getInstance
```
public static OnDemandService getInstance(DXEndpoint endpoint)
```
    Returns on-demand service for the specified DXEndpoint. Each DXEndpoint is conceptually associated with a single instance of on-demand service to control its historic data replay and this method returns this instance. The endpoint must have a role of FEED or ON_DEMAND_FEED.
    This method works only when the optional "dxfeed-ondemand.jar" is in the class-path.
    
    Parameters:
    
    endpoint - the endpoint.
    
    Returns:
    
    the on-demand service.
    
    Throws:
    
    UnsupportedOperationException - if "dxfeed-ondemand.jar" is not in the class-path.
    
    IllegalArgumentException - if the specified endpoint has unsupported class or wrong role.
  - initImpl
```
protected abstract void initImpl(DXEndpoint endpoint)
```
    Protected initialization method to bind OnDemandService instance to DXEndpoint instance. This method is invoked in implementation-specific fashion under implementation specific lock.
    
    Parameters:
    
    endpoint - the endpoint.
  - getEndpoint
```
public abstract DXEndpoint getEndpoint()
```
    Returns DXEndpoint that is associated with this on-demand service.
    
    Returns:
    
    DXEndpoint that is associated with this on-demand service.
  - isReplaySupported
```
public abstract boolean isReplaySupported()
```
    Returns true when on-demand historical data replay mode is supported. DXEndpoint should be connected to an address with "(ondemand:<address>)" component that specifies an on-demand historical data provider address. When this method returns false, replay method throws IllegalStateException.
    
    Returns:
    
    true when on-demand historical data replay mode is supported.
  - isReplay
```
public abstract boolean isReplay()
```
    Returns true when this on-demand historical data replay service is in replay mode. Replay mode is in effect after invocation of replay method and before invocation stopAndResume or stopAndClear methods.
    
    Returns:
    
    true when this on-demand historical data replay service is in replay mode.
  - isClear
```
public abstract boolean isClear()
```
    Returns true when this on-demand historical data replay service is in clear mode. Clear mode is in effect after invocation of stopAndClear() method and before invocation stopAndResume or replay methods.
    
    Returns:
    
    true when this on-demand historical data replay service is in clear mode.
  - getTime
```
public abstract Date getTime()
```
    Returns current or last on-demand historical data replay time. In replay mode this is the time that is being currently replayed, otherwise this is the last time that was replayed. If replay was never started, then result is new Date(0).
    
    Returns:
    
    current or last on-demand historical data replay time.
  - getSpeed
```
public abstract double getSpeed()
```
    Returns on-demand historical data replay speed. Speed is measured with respect to the real-time playback speed. The result of this method is zero when this service is not in replay mode. The speed is set when starting replay by replay(time, speed) method and with setSpeed(speed) method during replay.
    
    Returns:
    
    on-demand historical data replay speed.
  - replay
```
public final void replay(Date time)
```
    Turns on-demand historical data replay mode from a specified time with real-time speed. This is a shortcut for:
```
     replay(time, 1);
```
    This method can be used only when isReplaySupported() method returns true, that is when DXEndpoint is connected to an address with "(ondemand:<address>)" component that specifies an on-demand historical data provider address.
    Parameters:
    
    time - time to start replay from.
    
    Throws:
    
    IllegalStateException - when isReplaySupported() is false.
    
    NullPointerException - if time is null.
    
    See Also:
    
    replay(Date, double), isReplaySupported()
  - replay
```
public abstract void replay(Date time,
                            double speed)
```
    Turns on-demand historical data replay mode from a specified time and with a specified speed. This method can be used only when isReplaySupported() method returns true, that is when DXEndpoint is connected to an address with "(ondemand:<address>)" component that specifies an on-demand historical data provider address.
    After invocation of this method:
    - isReplay() returns true.
    - isClear() returns false.
    - getTime() returns time that is currently being replayed.
    - getSpeed() returns speed.
    Parameters:
    
    time - time to start replay from.
    
    speed - speed to start replay with. Use 1 for real-time speed, >1 for faster than real-time speed, <1 for slower than real-time speed, and 0 for pause.
    
    Throws:
    
    IllegalStateException - when isReplaySupported() is false.
    
    IllegalArgumentException - if speed < 0.
    
    NullPointerException - when if is null.
    
    See Also:
    
    isReplaySupported()
  - pause
```
public abstract void pause()
```
    Pauses on-demand historical data replay and keeps data snapshot. This method can only be called in replay mode. This is a shortcut for:
```
     setSpeed(0);
```
    This method atomically captures current replay time and pauses at it. After invocation of this method:
    - isReplay() returns true.
    - isClear() returns false.
    - getTime() returns time where replay was paused at.
    - getSpeed() returns 0.
    Throws:
    
    IllegalStateException - if on-demand service was not in replay mode.
  - stopAndResume
```
public abstract void stopAndResume()
```
    Stops on-demand historical data replay and resumes ordinary data feed. This method has no effect when invoked not in replay mode. After invocation of this method:
    - isReplay() returns false.
    - isClear() returns false.
    - getTime() returns last replayed time.
    - getSpeed() returns 0.
    To stop on-demand historical data replay without resuming ordinary data feed use either pause() to keep data snapshot or stopAndClear() to clear data.
    Note, that endpoints with a role of ON_DEMAND_FEED do not have an ordinary feed (they are essentially on-demand only) and thus stopAndResume method works like stopAndClear for them.
  - stopAndClear
```
public abstract void stopAndClear()
```
    Stops incoming data and clears it without resuming data updates. This method works both in on-demand historical data replay mode and for ordinary data feed. All incoming data updates are suspended and current data is cleared. After invocation of this method:
    - isReplay() returns false.
    - isClear() returns true.
    - getTime() returns last replayed time.
    - getSpeed() returns 0.
    Ordinary data feed can be resumed with stopAndResume() method and on-demand historical data replay can be continued with replay(...) method.
  - setSpeed
```
public abstract void setSpeed(double speed)
```
    Changes on-demand historical data replay speed while continuing replay at current getTime() time}. Speed is measured with respect to the real-time playback speed. This method can only be called with non-zero speed in replay mode.
    
    Parameters:
    
    speed - on-demand historical data replay speed.
    
    Throws:
    
    IllegalStateException - if on-demand service was not in replay mode and speed != 0.
    
    IllegalArgumentException - if speed < 0.
  - addPropertyChangeListener
```
public abstract void addPropertyChangeListener(PropertyChangeListener listener)
```
    Adds listener that is notified about changes in on-demand service properties. Notification will be performed using this endpoint's executor. The following properties are supported: replaySupported, replay, clear, speed, and time.
    Installed listener can be removed with removePropertyChangeListener method.
    
    Parameters:
    
    listener - the listener to add.
  - removePropertyChangeListener
```
public abstract void removePropertyChangeListener(PropertyChangeListener listener)
```
    Removes listener that is notified about changes in on-demand service properties. It removes the listener that was previously installed with addPropertyChangeListener method.
    
    Parameters:
    
    listener - the listener to remove.

Class OnDemandService

State and change notifications

Threads and locks

Implementation details

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

OnDemandService

Method Detail

getInstance

getInstance

initImpl

getEndpoint

isReplaySupported

isReplay

isClear

getTime

getSpeed

replay

replay

pause

stopAndResume

stopAndClear

setSpeed

addPropertyChangeListener

removePropertyChangeListener