please support the use of resolvable parameters in functional (reactive) Spring MVC endpoints

[joshlong]

Spring WebFlux and Spring MVC introduced functional style configuration models for HTTP endpoints in 2017.

    @Bean
    RouterFunction<ServerResponse> myMvcRouterFunction() {
        return route()
                .GET("/**", new HandlerFunction<ServerResponse>() {
                    @Override
                    public ServerResponse handle(ServerRequest request) throws Exception {
                        return ServerResponse.ok().body("hello world");
                    }
                })
                .build();
    }

obviously, you wouldn't normally write that code out long hand. You'd use a lambda.

    @Bean
    RouterFunction<ServerResponse> myMvcRouterFunction() {
        return route()
                .GET("/**",  _  ->  ServerResponse.ok().body("hello world"))
                .build();
    }

That's taken from a Spring MVC application, though it's basically the same in Spring Webflux.

However, as far as I can tell, it's not possible to benefit from the various parameter/return value/argument resolvers for Spring MVC/Spring Webflux controllers in this model. This means things like Spring Security's @RegisteredOAuth2AuthorizedClient OAuth2AuthorizedClient oac are inaccessible.

For at leas the argument / parameter resolvers, it might be nice to provide a singleton.

I am hoping you'd consider exposing those as proxied singletons, sort of like Spring Framework's EntityManager, so that I could inject a singleton bean (OAuth2AuthorizedClient), but behind the scenes it would be scoped to the currently authenticated user. This might even be as simple as a request scoped bean, though I feel (perhaps irrationally) that that's less ideal than a simple facade (or even a proxy) that just sources the right value for the currently authenticated user.

[joshlong]

this will have the knock-on benefit of working naturally with Spring Cloud Gateway's functional MVC endpoint integration, which provides static methods that plugin as handlers and filters in the Spring Framework functional MVC configuration style

[rwinch]

I really don't like request based proxies because it confuses users.

I wonder if we could have Spring Security put the value in a request attribute. The controllers would get it from the request attribute and we could provide some convenience mechanism for this to work with the route