[Spring Boot] Websocket 적용

실시간 정보 조회를 위하여 Websocket을 사용할 일이 있어 적용하였다. 

 

1. 의존성 추가

implementation 'org.springframework.boot:spring-boot-starter-websocket'

 

2. config 추가 

package com.hyeon.backend.config;

import com.hyeon.backend.controller.ws.WebsocketController;
import lombok.RequiredArgsConstructor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.socket.config.annotation.EnableWebSocket;
import org.springframework.web.socket.config.annotation.WebSocketConfigurer;
import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry;

@Configuration
@RequiredArgsConstructor
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {

  private final WebsocketController wsController;

  @Override
  public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
    // TODO: 필요에 따라 허용할 origin을 지정
    registry.addHandler(wsController, "/ws").setAllowedOrigins("*");
  }
}

 

3. Controller 추가 

package com.hyeon.backend.controller.ws;

import com.hyeon.backend.utils.Formatter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import lombok.extern.slf4j.Slf4j;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
import org.springframework.web.socket.CloseStatus;
import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler;

@Slf4j
@Component
@EnableScheduling
public class WebsocketController extends TextWebSocketHandler {

  private static List<WebSocketSession> list = new ArrayList<>();

  @Override
  protected void handleTextMessage(
    WebSocketSession session,
    TextMessage message
  ) throws Exception {
    String payload = message.getPayload();
    log.info("payload : " + payload);

    for (WebSocketSession sess : list) {
      if (!sess.getId().equals(session.getId())) {
        sess.sendMessage(message);
      }
    }
  }

  /* Client가 접속 시 호출되는 메서드 */
  @Override
  public void afterConnectionEstablished(WebSocketSession session)
    throws Exception {
    list.add(session);
    log.info("{} 클라이언트 접속", list.toString());
  }

  /* Client가 접속 해제 시 호출되는 메서드 */
  @Override
  public void afterConnectionClosed(
    WebSocketSession session,
    CloseStatus status
  ) throws Exception {
    list.remove(session);
  }

  @Scheduled(fixedRate = 1000)
  public void sendMetricsToClients() {
    try {
      String diskUsage = "0";
      String memoryUsage = "0";
      String cpuUsage = "0";

      for (WebSocketSession sess : list) {
        sess.sendMessage(
          new TextMessage(Formatter.formatJsonWithKey("diskUsage", diskUsage))
        );
        sess.sendMessage(
          new TextMessage(
            Formatter.formatJsonWithKey("memoryUsage", memoryUsage)
          )
        );
        sess.sendMessage(
          new TextMessage(Formatter.formatJsonWithKey("cpuUsage", cpuUsage))
        );
      }
    } catch (IOException e) {
      log.error("IOException occurred: {}", e.getMessage());
      // TODO: 웹소켓 서버 자체에서 에러가 발생하면 어떻게 할 것인지?
      // TODO: Retry?

    }
  }
}

 

 

4. TEST

https://piehost.com/websocket-tester

사이트에서 온라인 테스트

혹은 postman에서 테스트

다양한 방법이 있음

Online Websockets Tester - Debug Client Tool