메리

1. websocket 연결설정

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;

import lombok.RequiredArgsConstructor;

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

    //밑에서 만들 WebSocketHandler 클래스
    private final WebSocketHandler webSocketHandler;

    @Override
    public void registerWebSocketHandlers(WebSocketHandlerRegistry registry){
        registry.addHandler(webSocketHandler,"/websocket").setAllowedOrigins("*");
        // /websocket : 연결url
        //setAllowedOrigins : 웹소켓 cors정책으로, 허용 도메인 지정
        
    }

}

2. websocket 핸들러 생성. web socket 연결 및 종료의 수행에 대한 내용

import java.util.concurrent.ConcurrentHashMap;

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;

@Component
//TextWebSocketHandler 상속 시 3개의 메소드 오버라이딩
public class WebSocketHandler extends TextWebSocketHandler{
    
    //ConcurrentHashMap : 멀티 스레드 환경에서 사용. entry 아이템별로 락을 건다.
    private static final ConcurrentHashMap<String, WebSocketSession> CLIENTS = new ConcurrentHashMap<String, WebSocketSession>();
    
    public void afterConnectionEstablished(WebSocketSession session)throws Exception{
        CLIENTS.put(session.getId(), session);
        System.out.println("session Id(" + session.getId() + ") 연결");
        //출력예시 : session Id(84693265-e147-0b2c-5505-b2d3c62e62b4) 연결
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception{
        CLIENTS.remove(session.getId());
        System.out.println("session Id(" + session.getId() + ") 연결해제");
        //출력예시 : session Id(03017781-abf2-bc66-855e-f217bb99b275) 연결해제
    }

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception{
        String id = session.getId();
        System.out.println(CLIENTS.toString());
        //출력예시 : {03017781-abf2-bc66-855e-f217bb99b275=StandardWebSocketSession[id=03017781-abf2-bc66-855e-f217bb99b275, uri=ws://localhost:8081/websocket]}
        CLIENTS.entrySet().forEach(arg ->{
            if(!arg.getKey().equals(id)){
                try{
                    arg.getValue().sendMessage(message);
                }catch(Exception e){
                    e.printStackTrace();
                }
            }
        });
    }
}

테스트 방법

1. chrome에서 제공하는 확장 프로그램 이용

https://chromewebstore.google.com/detail/websocket-test-client/fgponpodhbmadfljofbimhhlengambbn?pli=1

2. postman에서 제공하는 웹소켓 연결 기능 이용