CODEWITHSUNDEEP
project-reactor
naval jain
naval jain

Reputation: 393

Call back to back Rest services using Spring WebFlux and resuse result from intermediate services?

I am new to Spring WebFlux but the I am trying to achieve that is specified below.

First Service -> AuthService  Mono<String> ->gives auth token
Second Service -> ServiceSecodn Uses output from above service
Third service -> Uses output from both above specified services.

Not able to express it using webFlux flatmap API

 service1.dologin().flatmap(info->service2.apiCall(info))

I want to make a third service call service3.apiCall(loginInfo,infoFromSecondServiceCall)

Upvotes: 0

Views: 745

Answers (1)

Oleh Dokuka
Oleh Dokuka

Reputation: 12184

Combine output using Tuple2 in order to combine several outputs

You may keep all information all the way by holding it in one structure as in the following example:

service1.dologin()
        .flatMap(lInfo ->
            service2.apiCall(lInfo)
                    .map(result -> Tuples.of(lInfo, result))
        )
        .flatMap(lInfoAndResultTuple -> 
            service3.apiCall(
                lInfoAndResultTuple.getT1(),
                lInfoAndResultTuple.getT2()
            )
        )

In this example, we use additional structure to keep required data all the way down. The main advantage of that example is a flat stream. The main disadvantage of that technique is an additional structure which makes harder to operate on data within it.

Using complex Closure Model

In turn, to avoid redundant data structure, we may use closure technique and always have access to the parent closure data as it is shown in the following example:

service1.dologin()
        .flatMap(lInfo ->
            service2.apiCall(lInfo)            
                    .flatMap(result -> 
                        service3.apiCall(lInfo, result)
                    )
        )

Comparing to the previous example, here we do not have to use an additional data structure in order to access upstream data. The Java Language provides us with build in access to the parents' closures data so that we may use it anytime in children's closures. The main advantage of that technique is the absence of redundant data structure. The main disadvantage is complex Flux/Closures structure which looks like well known Callback Hell

Upvotes: 1

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