Заготовка под отправку счетчиков

src/main/java/ru/serega6531/packmate/service/SubscriptionService.java

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+package ru.serega6531.packmate.service;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import lombok.extern.slf4j.Slf4j;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+import org.springframework.web.socket.TextMessage;
+import org.springframework.web.socket.WebSocketSession;
+import org.springframework.web.socket.sockjs.SockJsTransportFailureException;
+import ru.serega6531.packmate.model.pojo.SubscriptionMessage;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Objects;
+
+@Service
+@Slf4j
+public class SubscriptionService {
+
+    private final List<WebSocketSession> subscribers = Collections.synchronizedList(new ArrayList<>());
+
+    private final ObjectMapper mapper;
+
+    @Autowired
+    public SubscriptionService(ObjectMapper mapper) {
+        this.mapper = mapper;
+    }
+
+    public void addSubscriber(WebSocketSession session) {
+        subscribers.add(session);
+        log.info("User subscribed: {}", Objects.requireNonNull(session.getRemoteAddress()).getHostName());
+    }
+
+    public void removeSubscriber(WebSocketSession session) {
+        subscribers.remove(session);
+        log.info("User unsubscribed {}", Objects.requireNonNull(session.getRemoteAddress()).getHostName());
+    }
+
+    void broadcast(SubscriptionMessage message) {
+        subscribers.forEach(s -> {
+            try {
+                s.sendMessage(objectToTextMessage(message));
+            } catch (IOException | SockJsTransportFailureException e) {
+                log.warn("WS", e);
+            }
+        });
+    }
+
+    private TextMessage objectToTextMessage(SubscriptionMessage object) throws JsonProcessingException {
+        return new TextMessage(mapper.writeValueAsString(object));
+    }
+
+}