Response typing

Declare Request<R> on a query or command to state what its caller should receive. The compiler can then infer its result type, so callers need no casts.

Java

public record GetGreeting(String name) implements Request<String> {
    @HandleQuery
    String handle() { return "Hello, " + name + "!"; }
}

String greeting = Fluxzero.queryAndWait(new GetGreeting("Alice"));

Kotlin

data class GetGreeting(val name: String) : Request<String> {
    @HandleQuery
    fun handle() = "Hello, $name!"
}

val greeting = Fluxzero.queryAndWait(GetGreeting("Alice"))

The example keeps the handler on the query. Separate handlers can use the same request contract.

Typed tests

The fixture also knows the result type:

Java

TestFixture.create().whenQuery(new GetGreeting("Alice"))
        .expectResult(greeting -> greeting.startsWith("Hello"));

Kotlin

TestFixture.create().whenQuery(GetGreeting("Alice"))
    .expectResult { greeting: String -> greeting.startsWith("Hello") }

Handler compatibility

The SDK’s annotation processor checks the return types of annotated handlers against the request contract. Request<R> describes the response type; it does not register or create a handler. See message handling for handler registration and asynchronous results.