AbstractIndexedEventModel (dxFeed API 3.319)

java.lang.Object
- com.dxfeed.model.AbstractIndexedEventModel<E,N>

Type Parameters:

E - the type of events (entry values).

N - the type of concrete entries in the model.

All Implemented Interfaces:

AutoCloseable

Direct Known Subclasses:

IndexedEventModel
```
public abstract class AbstractIndexedEventModel<E extends IndexedEvent<?>,N extends AbstractIndexedEventModel.Entry<E>>
extends Object
implements AutoCloseable
```
Abstract model for a list of indexed events. This class handles all snapshot and transaction logic of IndexedEvent class and arranges incoming events into a list ordered by their source id and index. Note, that TimeSeriesEvent extends IndexedEvent in such a way, that this ordering also orders time-series event by time. However, there is a time-series aware class TimeSeriesEventModel that provides a more convenient way to subscribe to time-series.
This abstract class provides only protected methods to access the underlying list of events: size, get, listIterator, and entryListIterator, because it is designed for extension and is not designed for a direct use. For a concrete implementation use IndexedEventModel class.
The model must be configured with symbol to subscribe for and attached to a DXFeed instance to start operation.
Model change notifications are provided by an abstract modelChanged method that must be overridden in concrete implementation classes. This class also provides abstract createEntry method that must be overridden to return a fresh instance of an AbstractIndexedEventModel.Entry class that is used inside this class to wrap incoming events and may be augmented with an additional event-related information if needed.
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 get methods nor via modelChanged 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 indexed events directly via low-level DXFeedSubscription class.
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.
Notification on model changes 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
Modifier and Type Class and Description

static class AbstractIndexedEventModel.Entry<V>
Represents an internal entry in the model.

Nested Classes
Modifier and Type	Class and Description
`static class`	`AbstractIndexedEventModel.Entry<V>` Represents an internal entry in the model.

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`AbstractIndexedEventModel(Class<? extends E> eventType)` Creates new model.
`protected`	`AbstractIndexedEventModel(DXFeed feed, Class<? extends E> eventType)` Creates new model attached to the specified feed.

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`attach(DXFeed feed)` Attaches model to the specified feed.
`void`	`clear()` Clears subscription symbol and, subsequently, all events in this model.
`void`	`close()` Closes this model and makes it permanently detached.
`protected abstract N`	`createEntry()` Creates new concrete entry to represent an event in this model.
`void`	`detach(DXFeed feed)` Detaches model from the specified feed.
`protected ListIterator<N>`	`entryListIterator()` Returns a list iterator over the entries in this model (in proper sequence).
`protected E`	`get(int index)` Returns the element at the specified position in this model.
`Executor`	`getExecutor()` Returns executor for processing event notifications on this model.
`int`	`getSizeLimit()` Returns size limit of this model.
`Object`	`getSymbol()` Returns model subscription symbol, or `null` is not subscribed (this is a default value).
`protected boolean`	`isClosed()`
`protected boolean`	`isSnapshotEnd(E event)` Returns `true` when this event ends the snapshot.
`protected ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this model (in proper sequence).
`protected ListIterator<E>`	`listIterator(int index)` Returns a list iterator over the elements in this model (in proper sequence), starting at the specified position in the model.
`protected abstract void`	`modelChanged(List<N> changedEntries)` Invoked on the change of this model.
`void`	`setExecutor(Executor executor)` Changes executor for processing event notifications on this model.
`void`	`setSizeLimit(int sizeLimit)` Changes size limit of this model.
`void`	`setSymbol(Object symbol)` Changes symbol for this model to subscribe for.
`protected int`	`size()` Returns the number of elements in this model.

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

- Constructor Detail
  - AbstractIndexedEventModel
```
protected AbstractIndexedEventModel(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 and 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.
  - AbstractIndexedEventModel
```
protected AbstractIndexedEventModel(DXFeed feed,
                                    Class<? extends E> eventType)
```
    Creates new model attached to the specified feed. It is not subscribed to any symbol. Use setSymbol(java.lang.Object) to specify subscription symbol.
    
    Parameters:
    
    feed - feed to attach to.
    
    eventType - the event type.
    
    Throws:
    
    NullPointerException - if event type is null.
- Method Detail
  - attach
```
public void attach(DXFeed feed)
```
    Attaches model to the specified feed.
    
    Parameters:
    
    feed - feed to attach to.
  - detach
```
public void detach(DXFeed feed)
```
    Detaches model from the specified feed.
    
    Parameters:
    
    feed - feed to detach from.
  - isClosed
```
protected boolean isClosed()
```
  - close
```
public void close()
```
    Closes this model and makes it permanently detached.
    This method ensures that model can be safely garbage-collected when all outside references to it are lost.
    
    Specified by:
    
    close in interface AutoCloseable
  - getExecutor
```
public Executor getExecutor()
```
    Returns executor for processing event notifications on this model. See Threads and locks section of this class documentation.
    
    Returns:
    
    executor for processing event notifications on this model, or null if default executor of the attached DXFeed is used.
  - setExecutor
```
public void setExecutor(Executor executor)
```
    Changes executor for processing event notifications on this model. See Threads and locks section of this class documentation.
    
    Parameters:
    
    executor - executor for processing event notifications on this model, or null if default executor of the attached DXFeed is used.
  - clear
```
public void clear()
```
    Clears subscription symbol and, subsequently, all events in this model. This is a shortcut for setSymbol(null).
  - getSymbol
```
public Object getSymbol()
```
    Returns model subscription symbol, or null is not subscribed (this is a default value).
    
    Returns:
    
    model subscription symbol.
  - setSymbol
```
public void setSymbol(Object symbol)
```
    Changes symbol for this model to subscribe for.
    
    Parameters:
    
    symbol - model subscription symbol, use null to unsubscribe.
  - getSizeLimit
```
public int getSizeLimit()
```
    Returns size limit of this model. It is equal to Integer.MAX_VALUE by default (no limit).
    
    Returns:
    
    size limit of this model.
  - setSizeLimit
```
public void setSizeLimit(int sizeLimit)
```
    Changes size limit of this model. When size limit is exceed, the first entries from this model are dropped.
    
    Parameters:
    
    sizeLimit - size limit of this model.
    
    Throws:
    
    IllegalArgumentException - if sizeLimit is negative.
  - size
```
protected int size()
```
    Returns the number of elements in this model. It is limited by sizeLimit property.
    
    Returns:
    
    the number of elements in this model.
  - get
```
protected E get(int index)
```
    Returns the element at the specified position in this model.
    
    Parameters:
    
    index - index of the element to return.
    
    Returns:
    
    the element at the specified position in this model.
    
    Throws:
    
    IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size()).
  - listIterator
```
protected ListIterator<E> listIterator()
```
    Returns a list iterator over the elements in this model (in proper sequence).
    
    Returns:
    
    a list iterator over the elements in this model (in proper sequence).
  - listIterator
```
protected ListIterator<E> listIterator(int index)
```
    Returns a list iterator over the elements in this model (in proper sequence), starting at the specified position in the model.
    
    Parameters:
    
    index - index of the first element to be returned from the list iterator (by a call to next).
    
    Returns:
    
    a list iterator over the elements in this model (in proper sequence), starting at the specified position in the model.
    
    Throws:
    
    IndexOutOfBoundsException - if the index is out of range (index < 0 || index > size()).
  - entryListIterator
```
protected ListIterator<N> entryListIterator()
```
    Returns a list iterator over the entries in this model (in proper sequence).
    
    Returns:
    
    a list iterator over the entries in this model (in proper sequence).
  - createEntry
```
protected abstract N createEntry()
```
    Creates new concrete entry to represent an event in this model.
    
    Returns:
    
    new entry to represent an event in this model.
  - modelChanged
```
protected abstract void modelChanged(List<N> changedEntries)
```
    Invoked on the change of this model. All the entries in the changedEntries list have changed flag set to true and the new values of incoming events are available via Entry.getNewValue method. The changed flags is cleared after return from this method by Entry.commitChange method, which can also be invoked during this method, if needed.
    
    Parameters:
    
    changedEntries - the list of changed entries.
  - isSnapshotEnd
```
protected boolean isSnapshotEnd(E event)
```
    Returns true when this event ends the snapshot. This implementations return true when either SNAPSHOT_END or SNAPSHOT_SNIP flag is set in eventFlags.

Class AbstractIndexedEventModel<E extends IndexedEvent<?>,N extends AbstractIndexedEventModel.Entry<E>>

Resource management and closed models

Threads and locks

Nested Class Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

AbstractIndexedEventModel

AbstractIndexedEventModel

Method Detail

attach

detach

isClosed

close

getExecutor

setExecutor

clear

getSymbol

setSymbol

getSizeLimit

setSizeLimit

size

get

listIterator

listIterator

entryListIterator

createEntry

modelChanged

isSnapshotEnd