Package io.objectbox.query

Class QueryPublisher<T>

java.lang.Object

io.objectbox.query.QueryPublisher<T>

All Implemented Interfaces:

DataPublisher<List<T>>, Runnable

@Internal
class QueryPublisher<T>
extends Object
implements DataPublisher<List<T>>, Runnable

A DataPublisher that subscribes to an ObjectClassPublisher if there is at least one observer. Publishing is requested if the ObjectClassPublisher reports changes, a subscription is observed or Query.publish() is called. For publishing the query is re-run and the result delivered to the current observers. Results are published on a single thread, one at a time, in the order publishing was requested.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
private static class	QueryPublisher.SubscribedObservers<T>

Field Summary

Fields

Modifier and Type	Field	Description
private final Box<T>	box
private DataObserver<Class<T>>	objectClassObserver
private DataSubscription	objectClassSubscription
private final Set<DataObserver<List<T>>>	observers
private boolean	publisherRunning
private final Deque<DataObserver<List<T>>>	publishQueue
private final Query<T>	query
private final QueryPublisher.SubscribedObservers<T>	SUBSCRIBED_OBSERVERS	Placeholder observer to use if all subscribed observers should be notified.

Constructor Summary

Constructors

Constructor	Description
QueryPublisher(Query<T> query, Box<T> box)

Method Summary

Modifier and Type	Method	Description
(package private) void	publish()
void	publishSingle(DataObserver<List<T>> observer, Object param)
private void	queueObserverAndScheduleRun(DataObserver<List<T>> observer)	Non-blocking: will just enqueue the changes for a separate thread.
void	run()	Processes publish requests for this query on a single thread to prevent older query results getting delivered after newer query results.
void	subscribe(DataObserver<List<T>> observer, Object param)
void	unsubscribe(DataObserver<List<T>> observer, Object param)

Methods inherited from class java.lang.Object

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

Field Details

query

private final Query<T> query

box

private final Box<T> box

observers

private final Set<DataObserver<List<T>>> observers

publishQueue

private final Deque<DataObserver<List<T>>> publishQueue

publisherRunning

private volatile boolean publisherRunning

SUBSCRIBED_OBSERVERS

private final QueryPublisher.SubscribedObservers<T> SUBSCRIBED_OBSERVERS

Placeholder observer to use if all subscribed observers should be notified.

objectClassObserver

private DataObserver<Class<T>> objectClassObserver

objectClassSubscription

private DataSubscription objectClassSubscription

Constructor Details

QueryPublisher

QueryPublisher(Query<T> query,
 Box<T> box)

Method Details

subscribe

public void subscribe(DataObserver<List<T>> observer,
 @Nullable
 Object param)

Specified by:

subscribe in interface DataPublisher<T>

publishSingle

public void publishSingle(DataObserver<List<T>> observer,
 @Nullable
 Object param)

Specified by:

publishSingle in interface DataPublisher<T>

publish

void publish()

queueObserverAndScheduleRun

private void queueObserverAndScheduleRun(DataObserver<List<T>> observer)

Non-blocking: will just enqueue the changes for a separate thread.

run

public void run()

Processes publish requests for this query on a single thread to prevent older query results getting delivered after newer query results. To speed up processing each loop publishes to all queued observers instead of just the next in line. This reduces time spent querying and waiting for DataObserver.onData() and their potential DataTransformers.

Specified by:

run in interface Runnable

unsubscribe

public void unsubscribe(DataObserver<List<T>> observer,
 @Nullable
 Object param)

Specified by:

unsubscribe in interface DataPublisher<T>