Interface HandlerRegistry

All Superinterfaces:

HasLocalHandlers

All Known Implementing Classes:

HandlerRegistry.MergedHandlerRegistry, HandlerRegistry.NoOpHandlerRegistry, LocalHandlerRegistry

public interface HandlerRegistry
extends HasLocalHandlers

Interface for registering and invoking local message handlers.

A HandlerRegistry is responsible for managing one or more message handlers — including discovery, invocation, and filtering logic. It is a central abstraction in scenarios where handlers are registered programmatically (e.g. embedded services, tests, functional configurations).

Responsibilities

• Registering local handler instances (e.g. beans, stateful components)
• Dispatching messages to matching handlers
• Composing multiple registries to form a combined resolution chain
• Delegating filtering behavior via HandlerFilter

Usage

Handlers can be registered using HasLocalHandlers.registerHandler(Object) or HasLocalHandlers.registerHandler(Object, HandlerFilter). Message handling can be triggered manually via handle(DeserializingMessage).

HandlerRegistry registry = ...;
registry.registerHandler(new MyCommandHandler());

registry.handle(myMessage).ifPresent(resultFuture -> {
    Object result = resultFuture.join();
    ...
});

Composing Registries

Use andThen(HandlerRegistry) or orThen(HandlerRegistry) to chain multiple registries:

• andThen: invokes both registries and merges results (e.g. for broadcasting)
• orThen: invokes the second only if the first produces no result

HandlerRegistry composite = registry1.orThen(registry2);

Built-in Implementations

• HandlerRegistry.NoOpHandlerRegistry — a stub that does nothing, always returns empty
• HandlerRegistry.MergedHandlerRegistry — combines two registries into one

See Also:

• HasLocalHandlers
• HandlerFilter
• DeserializingMessage

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static class	HandlerRegistry.MergedHandlerRegistry	Combines two HandlerRegistry instances into one.
static enum	HandlerRegistry.NoOpHandlerRegistry	A no-op handler registry that performs no registration or dispatch.

Method Summary

Modifier and Type	Method	Description
default HandlerRegistry	andThen(HandlerRegistry next)	Creates a composite registry that invokes both this and the given registry.
Optional<CompletableFuture<Object>>	handle(DeserializingMessage message)	Attempts to handle the given message using local handlers.
static HandlerRegistry	noOp()	A no-op registry that does not register or invoke any handlers.
default HandlerRegistry	orThen(HandlerRegistry next)	Creates a fallback registry that only invokes the given registry if this one yields no result.

Methods inherited from interface HasLocalHandlers

hasLocalHandlers, registerHandler, registerHandler, setSelfHandlerFilter

Method Details

noOp

static HandlerRegistry noOp()

A no-op registry that does not register or invoke any handlers.

handle

Optional<CompletableFuture<Object>> handle(DeserializingMessage message)

Attempts to handle the given message using local handlers.

Parameters:

message - the deserialized message to dispatch

Returns:

an optional future containing the result, or empty if no handler was found

andThen

default HandlerRegistry andThen(HandlerRegistry next)

Creates a composite registry that invokes both this and the given registry.

Results are merged via thenCombine() if both registries handle the message.

Parameters:

next - the registry to invoke second

Returns:

a combined registry

orThen

default HandlerRegistry orThen(HandlerRegistry next)

Creates a fallback registry that only invokes the given registry if this one yields no result.

Parameters:

next - the fallback registry

Returns:

a combined registry with short-circuiting behavior