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The Kotlin serverside code the WebSocket implementation
package codemwnci.bootsocket
import com.fasterxml.jackson.databind.ObjectMapper
import com.fasterxml.jackson.module.kotlin.jacksonObjectMapper
import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Configuration
import org.springframework.web.socket.*
import org.springframework.web.socket.config.annotation.*
import org.springframework.web.socket.handler.TextWebSocketHandler
import java.util.concurrent.atomic.AtomicLong
class User(val id: Long, val name: String)
class Message(val msgType: String, val data: Any)
class ChatHandler : TextWebSocketHandler() {
val sessionList = HashMap<WebSocketSession, User>()
var uids = AtomicLong(0)
override fun afterConnectionClosed(session: WebSocketSession, status: CloseStatus) {
sessionList -= session
public override fun handleTextMessage(session: WebSocketSession?, message: TextMessage?) {
val json = ObjectMapper().readTree(message?.payload)
// {type: "join/say", data: "name/msg"}
when (json.get("type").asText()) {
"join" -> {
val user = User(uids.getAndIncrement(), json.get("data").asText())
sessionList.put(session!!, user)
// tell this user about all other users
emit(session, Message("users", sessionList.values))
// tell all other users, about this user
broadcastToOthers(session, Message("join", user))
"say" -> {
broadcast(Message("say", json.get("data").asText()))
fun emit(session: WebSocketSession, msg: Message) = session.sendMessage(TextMessage(jacksonObjectMapper().writeValueAsString(msg)))
fun broadcast(msg: Message) = sessionList.forEach { emit(it.key, msg) }
fun broadcastToOthers(me: WebSocketSession, msg: Message) = sessionList.filterNot { it.key == me }.forEach { emit(it.key, msg) }
@Configuration @EnableWebSocket
class WSConfig : WebSocketConfigurer {
override fun registerWebSocketHandlers(registry: WebSocketHandlerRegistry) {
registry.addHandler(ChatHandler(), "/chat").withSockJS()
class ChatApplication
fun main(args: Array<String>) {
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