I’m learning spring boot with Kotlin and I’m tryin...

# spring

[dany giguere]

I’m learning spring boot with Kotlin and I’m trying to do a WebClient call with Flux. I have these methods in a controller:

@GetMapping("/slow-service-users")
    fun getAllUsers(): List<User?>? {
        Thread.sleep(2000L) // delay
        return userRepository.findAll()
    }

    @GetMapping(value = ["/users-non-blocking"])
    fun getUsersNonBlocking(): Flux<User?>? {
        <http://logger.info|logger.info>("Starting NON-BLOCKING Controller!")
        val userFlux: Flux<User?> = WebClient.create()
            .get()
            .uri("<http://localhost:8080/slow-service-users>")
            .retrieve()
            .bodyToFlux(User::class.java)
        userFlux.subscribe { user -> <http://logger.info|logger.info>(user.toString()) }
        <http://logger.info|logger.info>("Exiting NON-BLOCKING Controller!")
        return userFlux
    }

/slow-service-users returns a proper response. But when I call /users-non-blocking, I get this error:

"org.springframework.web.reactive.function.client.WebClientResponseException: 200 OK from GET <http://localhost:8080/slow-service-users>; nested exception is org.springframework.web.reactive.function.UnsupportedMediaTypeException: Content type 'application/json' not supported for bodyType=com.example.app.models.User

How can I fix this Content type 'application/json' not supported for bodyType error ? The project repo is here: https://github.com/danygiguere/springboot-kotlin-example.
The user model is:

@Entity
class User {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    var id: Long? = null

    var username = ""

    @Column(unique = true)
    var email = ""

    var password = ""
        @JsonIgnore
        get() = field
        set(value) {
            val passwordEncoder = BCryptPasswordEncoder()
            field = passwordEncoder.encode(value)
        }

    fun comparePassword(password: String): Boolean {
        return BCryptPasswordEncoder().matches(password, this.password)
    }

    val firstName: String = ""

    val lastName: String = ""

    @JsonManagedReference
    @OneToMany(cascade = [(CascadeType.ALL)], orphanRemoval = true, fetch = FetchType.EAGER)
    @JoinColumn(name = "userId", referencedColumnName = "id")
    var posts: List<Post>? = null
}

[Giorgos Makris]

i know this is not directly tied to your question but your endpoints should return Mono<ServerResponse>

[Giorgos Makris]

if you are interest i could bring up an example i have laying around of how i got it set up

[dany giguere]

you mean Mono… instead of Flux<User?> ?

[kqr]

I would try to define content type on endpoint via @GetMapping(produces=application/json) and in webclient define header ACCEPT to application/json

[Giorgos Makris]

@dany giguere yeah that's what i mean, your endpoints return a single server response where the body is the Flux<User>

[dany giguere]

ok thanks guys. tried addding application/json and also changing to Mono but I sill have the same error. Here is my function now:

@GetMapping(value = ["/users-non-blocking"], produces = ["application/json"])
    fun getUsersNonBlocking(): Mono<User> {
        <http://logger.info|logger.info>("Starting NON-BLOCKING Controller!")
        val userFlux: Mono<User> = WebClient.create()
            .get()
            .uri("<http://localhost:8080/slow-service-users>")
            .header("ACCEPT", "application/json")
            .retrieve()
            .bodyToMono(User::class.java)
        userFlux.subscribe { user -> <http://logger.info|logger.info>(user.toString()) }
        <http://logger.info|logger.info>("Exiting NON-BLOCKING Controller!")
        return userFlux
    }

[kqr]

just to be sure, you have produces on slow-service too?

[dany giguere]

yes Jakub, I do have the produces = [“application/json”] as well on the slow-service too

[kqr]

if you call your slow endpoint via insomnia/postman how does response look like?

[dany giguere]

I get a 200 with the proper payload:

[
    {
        "id": 1,
        "username": "johndoe1",
        "email": "<mailto:[e-mail]|[e-mail]>",
        "firstName": "",
     ...
]

[kqr]

does this work https://stackoverflow.com/a/54014312/1462417

[dany giguere]

thanks a lot @kqr. Indeed I had to pass something like an array. This works now :

@GetMapping("/slow-service-users")
    fun getAllUsers(): List<User?>? {
//        Thread.sleep(2000L) // delay
        return userRepository.findAll()
    }

    @GetMapping(value = ["/users-non-blocking"])
    fun getUsersNonBlocking(): Mono<ArrayList<*>> {
        <http://logger.info|logger.info>("Starting NON-BLOCKING Controller!")
        val userFlux: Mono<ArrayList<*>> = WebClient.create()
            .get()
            .uri("<http://localhost:8080/slow-service-users>")
            .retrieve()
            .bodyToMono(ArrayList::class.java)
        userFlux.subscribe { user -> <http://logger.info|logger.info>(user.toString()) }
        <http://logger.info|logger.info>("Exiting NON-BLOCKING Controller!")
        return userFlux
    }