Spring Reactive SSE Example (https://blog.davidvassallo.me/3170)

DefaultRouter.kt

package com.example.sse.routers

import com.example.sse.HomeHandler
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.http.MediaType
import org.springframework.web.reactive.function.server.HandlerFunction
import org.springframework.web.reactive.function.server.RequestPredicates
import org.springframework.web.reactive.function.server.RouterFunction
import org.springframework.web.reactive.function.server.RouterFunctions
import org.springframework.web.reactive.function.server.ServerResponse


@Configuration
class DefaultRouter{

    @Bean
    fun route(homeHandler: HomeHandler): RouterFunction<ServerResponse> {

        return RouterFunctions
                .route(RequestPredicates.GET("/sse").and(RequestPredicates.accept(MediaType.TEXT_PLAIN)),
                                    HandlerFunction<ServerResponse> { homeHandler.ssEvents(it) })

    }
}

HomeHandler.kt

package com.example.sse.handlers

import com.example.sse.services.ServerSideEvents
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.http.MediaType
import org.springframework.http.codec.multipart.FilePart
import org.springframework.http.codec.multipart.Part
import org.springframework.stereotype.Component
import org.springframework.web.reactive.function.BodyExtractors
import org.springframework.web.reactive.function.BodyInserters
import org.springframework.web.reactive.function.server.ServerRequest
import org.springframework.web.reactive.function.server.ServerResponse
import org.springframework.web.reactive.function.server.bodyToServerSentEvents

import reactor.core.publisher.Mono


@Component
class HomeHandler {

    @Autowired
    var sseService : ServerSideEvents ?= null

    fun ssEvents(request: ServerRequest): Mono<ServerResponse> {
        val sseEvents = sseService!!.getSSE()
        println(request.headers().host().toString())
        return ServerResponse.ok().bodyToServerSentEvents(sseEvents)
    }
  
}