19/04/2022: Feign Reactive does not currently have support for Spring Boot 3. See the issues on github

I'm finding this question incomplete without proper usage example of how things should be set up.

Since op did not mention target language I'm feeling like to share Kotlin setup that works in my case:

build.gradle.kts

implementation("org.springframework.boot:spring-boot-starter-webflux")
implementation("com.playtika.reactivefeign:feign-reactor-core:3.2.1")
implementation("com.playtika.reactivefeign:feign-reactor-spring-configuration:3.2.1")
implementation("com.playtika.reactivefeign:feign-reactor-webclient:3.2.1")

Config.kt

@Configuration
@EnableWebFlux
@EnableReactiveFeignClients
class Config {
}

MyFeignClient.kt

@Component
@ReactiveFeignClient(
        url = "\${package.service.my-service-url}",
        name = "client"
)
interface MyFeignClient {
    @GetMapping(value = ["/my/url?my_param={my_value}"], consumes = ["application/json"])
    fun getValues(
            @PathVariable(name = "my_value") myValue: String?,
        ): Mono<MyEntity?>?
}

Then here goes code in some service class:

val myClient: MyFeignClient = WebReactiveFeign.builder<MyFeignClient>()
        .contract(ReactiveContract(SpringMvcContract()))
        .target(MyFeignClient::class.java, "http://example.com")
// feel free to add .block() to get unpacked value or just chain your logic further
val response = myClient.getValues(param)