Interface ProtocolExtension<T extends BabelProtocol>

Type Parameters:

T - the protocol type this extension targets

All Superinterfaces:

EventHandler<ProtocolEvent>

All Known Implementing Classes:

BroadcastConsumerExtension, BroadcastProviderExtension, MembershipConsumerExtension, MembershipProviderExtension, ResolverProviderExtension, SignedMessageExtension

public interface ProtocolExtension<T extends BabelProtocol>
extends EventHandler<ProtocolEvent>

A pluggable cross-cutting extension that augments a BabelProtocol with additional event handling capabilities.

Extensions allow the Babel runtime to wire up higher-level abstractions (e.g., broadcast, membership) on top of raw ProtocolEvents without requiring protocol implementations to extend a concrete base class. Each extension declares:

• which method-level Annotations it recognises via annotationClass(), so that SharedExecutorProtocolHolder can invoke register(Method, MethodHandles.Lookup, T, BabelProtocolHolder, Annotation) during initialisation;
• which ProtocolEvent types it wants to intercept via eventsClass(), so that the holder routes those events through handleEvent(ProtocolEvent) instead of the protocol's own handler map.

Concrete implementations are paired with a ProtocolExtensionFactory and registered on the BabelBootstrap before building the runtime.

See Also:

• BroadcastConsumerExtension
• MembershipConsumerExtension

Field Summary

Fields inherited from interface EventHandler

HANDLER_METHOD_NAME

Modifier and Type	Field	Description
static final String	HANDLER_METHOD_NAME	The name of the functional method.

Method Summary

Modifier and Type	Method	Description
default Set<Class<? extends Annotation>>	annotationClass()	Returns the set of method-level annotation types that this extension processes.
default Set<Class<? extends ProtocolEvent>>	eventsClass()	Returns the set of ProtocolEvent types that this extension handles.
default void	handleEvent(ProtocolEvent event)	Dispatches a ProtocolEvent that was previously claimed by this extension (because its type is listed in eventsClass()).
default void	register(Method method, MethodHandles.Lookup lookup, T protocol, BabelProtocolHolder holder, Annotation annotation)	Called by SharedExecutorProtocolHolder during initialisation for each method on the protocol that carries one of the annotations returned by annotationClass().

Method Details

register

default void register(Method method,
 MethodHandles.Lookup lookup,
 T protocol,
 BabelProtocolHolder holder,
 Annotation annotation)

Called by SharedExecutorProtocolHolder during initialisation for each method on the protocol that carries one of the annotations returned by annotationClass(). Implementations should build and store a handler for that method.

Parameters:

method - the annotated method on the protocol class

lookup - a MethodHandles.Lookup scoped to the protocol's class, suitable for creating lambda method handles

protocol - the concrete protocol instance

holder - the SharedExecutorProtocolHolder wrapping the protocol, which exposes AbstractBabelProtocolHolder.createHandler(Method, MethodHandles.Lookup, Class, Class, String, Class[], Class[]) for building typed functional-interface handlers

annotation - the Annotation that is associated with this method.

handleEvent

default void handleEvent(ProtocolEvent event)

Dispatches a ProtocolEvent that was previously claimed by this extension (because its type is listed in eventsClass()).

Specified by:

handleEvent in interface EventHandler<T extends BabelProtocol>

Parameters:

event - the event to handle; its runtime type is guaranteed to be one of the types returned by eventsClass()

annotationClass

default Set<Class<? extends Annotation>> annotationClass()

Returns the set of method-level annotation types that this extension processes. The framework scans protocol methods for these annotations during initialisation and calls register(Method, MethodHandles.Lookup, T, BabelProtocolHolder, Annotation) for each match.

Returns:

a list of annotation classes; may be empty if the extension does not use method annotations

eventsClass

default Set<Class<? extends ProtocolEvent>> eventsClass()

Returns the set of ProtocolEvent types that this extension handles. Events of these types are routed to handleEvent(ProtocolEvent) instead of the protocol's own @UponBabelEvent-annotated handlers.

Returns:

a list of event classes; may be empty