Package discord4j.core.event

Class DefaultEventDispatcher

java.lang.Object

discord4j.core.event.DefaultEventDispatcher

All Implemented Interfaces:

EventDispatcher

public class DefaultEventDispatcher
extends Object
implements EventDispatcher

Distributes events to subscribers using a Reactor FluxProcessor as backend.

The underlying processor can be configured at construction time. Thread affinity can also be configured by supplying a Scheduler, while an FluxSink.OverflowStrategy is applied to handle back-pressure of inbound Events, especially during startup.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	DefaultEventDispatcher.Builder	A builder to create EventDispatcher instances.

Field Summary

Fields inherited from interface discord4j.core.event.EventDispatcher

DEFAULT_EVENT_SCHEDULER

Constructor Summary

Constructors

Constructor	Description
DefaultEventDispatcher(FluxProcessor<Event,Event> eventProcessor, FluxSink.OverflowStrategy overflowStrategy, Scheduler eventScheduler)	Creates a new event dispatcher using the given FluxProcessor, backpressure-handling strategy and threading model.

Method Summary

Modifier and Type	Method	Description
<E extends Event> Flux<E>	on(Class<E> eventClass)	Retrieves a Flux with elements of the given Event type.
void	publish(Event event)	Publishes an Event to the dispatcher.
void	shutdown()	Signal that this event dispatcher must terminate and release its resources.

Methods inherited from class java.lang.Object

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

Methods inherited from interface discord4j.core.event.EventDispatcher

on, on

Constructor Detail

DefaultEventDispatcher

public DefaultEventDispatcher(FluxProcessor<Event,Event> eventProcessor,
                              FluxSink.OverflowStrategy overflowStrategy,
                              Scheduler eventScheduler)

Creates a new event dispatcher using the given FluxProcessor, backpressure-handling strategy and threading model.

Parameters:

eventProcessor - a FluxProcessor of Event, used to bridge gateway events to the dispatcher subscribers

overflowStrategy - an overflow strategy, see FluxSink.OverflowStrategy for the available strategies

eventScheduler - a Scheduler to ensure a certain thread model on each published signal

Method Detail

on

public <E extends Event> Flux<E> on(Class<E> eventClass)

Description copied from interface: EventDispatcher

Retrieves a Flux with elements of the given Event type. This Flux has to be subscribed to in order to start processing. See Event class for the list of possible event classes.

Note: Errors occurring while processing events will terminate your sequence. If you wish to use a version capable of handling errors for you, use EventDispatcher.on(Class, Function). See Reactive Streams Spec explaining this behavior.

A recommended pattern to use this method is wrapping your code that may throw exceptions within a flatMap block and use Mono.onErrorResume(Function), Flux.onErrorResume(Function) or equivalent methods to maintain the sequence active:

 client.getEventDispatcher().on(MessageCreateEvent.class)
     .flatMap(event -> myCodeThatMightThrow(event)
             .onErrorResume(error -> {
                 // log and then discard the error to keep the sequence alive
                 log.error("Failed to handle event!", error);
                 return Mono.empty();
             }))
     .subscribe();
 

For more alternatives to handling errors, please see Error Handling wiki page.

Specified by:

on in interface EventDispatcher

Type Parameters:

E - the type of the event class

Parameters:

eventClass - the event class to obtain events from

Returns:

a new Flux with the requested events

publish

public void publish(Event event)

Description copied from interface: EventDispatcher

Publishes an Event to the dispatcher. Might throw an unchecked exception if the dispatcher can't handle this event.

Specified by:

publish in interface EventDispatcher

Parameters:

event - the Event to publish

shutdown

public void shutdown()

Description copied from interface: EventDispatcher

Signal that this event dispatcher must terminate and release its resources.

Specified by:

shutdown in interface EventDispatcher