Spring Boot

MediatorK integrates with Spring Boot without any special plugin — just register handlers as beans and create the mediator in a @Configuration class.

See the full Spring Boot example for a complete WebFlux CRUD API.

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Setup

For the MediatorK dependency see Installation. For Spring Boot itself, follow the official Spring Initializr setup — select Kotlin, Gradle, and the Spring WebFlux starter.

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Pattern

1. Handler beans

@Service
class GetUserHandler(private val repo: UserRepository) : RequestHandler<GetUserQuery, User> {
    override suspend fun handle(mediator: Mediator, ctx: RequestContext, request: GetUserQuery) =
        repo.findById(request.id) ?: error("Not found")
}

2. Registrar bean

Group all handlers into a MediatorRegistrar:

@Component
class UserRegistrar(
    private val getUser: GetUserHandler,
    private val createUser: CreateUserHandler,
) : MediatorRegistrar {
    override fun register(registry: HandlerRegistry) {
        registry.scope {
            +getUser
            +createUser
        }
    }
}

3. Mediator bean

Spring collects all MediatorRegistrar beans automatically:

@Configuration
class MediatorConfig(private val registrars: List<MediatorRegistrar>) {
    @Bean
    fun mediator(): Mediator = MediatorFactory.create(
        registrars = registrars,
        pipelineBehaviors = listOf(LoggingBehavior()),
    )
}

4. Controller

@RestController
@RequestMapping("/users")
class UserController(private val mediator: Mediator) {

    @GetMapping("/{id}")
    suspend fun get(@PathVariable id: String) = mediator.send(GetUserQuery(id))

    @PostMapping
    suspend fun create(@RequestBody body: CreateUserRequest) =
        mediator.send(CreateUserCommand(body.name, body.email))
}

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Sample — Prayer Times API

The /samples/sample-spring module is a runnable Spring Boot WebFlux application that fetches prayer times and Islamic calendar months from the Aladhan API. It mirrors the Android sample structure in three layers:

Layer	Routes	Pattern
Before	/before/prayer-times/{city} · /before/islamic-months	Controller → UseCase → Repository → DataSource
After	/after/prayer-times/{city} · /after/islamic-months	Controller → Mediator → Handler
After Super	/aftersuper/prayer-times/{city} · /aftersuper/islamic-months	After + all pipeline behaviors

# Run (from the repo root)
./gradlew :samples:sample-spring:bootRun

# Try it
curl http://localhost:8081/before/prayer-times/London
curl http://localhost:8081/after/prayer-times/London
curl http://localhost:8081/aftersuper/prayer-times/London

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Next

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