Decorate webclient response using reactive context

Question

I'm trying to pass a parameter through the webClient context to understand how the reactive context works.

    .post()
    .uri(uri)
    .headers(httpHeaders -> httpHeaders.putAll(headers))
    .body(BodyInserters.fromObject(payload))
    .exchange()
    .flatMap( s -> Mono.subscriberContext()
        .map( ctx -> {
            System.out.println(“SubscriberContext1 " + ctx.getOrDefault("test", "DefaultValue”));
            return s;
        }))
    .flatMap(resp -> {
         return resp
            .bodyToMono(Object.class)
            .defaultIfEmpty(new HashMap<>())
            .map(body -> {
                //I would like to access the context variable here
                return doSomething(body, contextVariable);
            });})
    .flatMap( s -> Mono.subscriberContext()
        .map( ctx -> {
            System.out.println("SubscriberContext2” + ctx.getOrDefault("test", "DefaultValue”));
            return s;
        }))
    .subscriberContext(ctx -> {
        System.out.println("WRITE TEST");
        ctx.put("test", "test");
        return ctx;
    });

This prints out:

WRITE TEST
SubscriberContext1 DefaultValue
SubscriberContext2 DefaultValue

I'd expect it to be:

WRITE TEST
SubscriberContext1 test
SubscriberContext2 test

Why is the context variable not accessible within the flatMap?

Answer 1

ctx.put creates a new context. Changing the code to:

 .subscriberContext(ctx -> {
        System.out.println("WRITE TEST");
        return ctx.put("test", "test");

    });

solves it.