java - CopyOnWriteArrayList 为零而不是实际大小？

Question

可能很简单，但我自己无法弄清楚。我有一些 Spring Boot WebSockets 实现示例，并且想要显示总 Activity session 。所以我创建了@Scheduled activeSessions任务，它应该显示实际计数，但它始终为 0。当 afterConnectionEstablished称为我得到预期的 session 大小。有什么问题吗？

@Configuration
public class Monitoring extends TextWebSocketHandler {

    private List<WebSocketSession> sessions = new CopyOnWriteArrayList<>();

    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message)
            throws Exception {

        String clientMessage = message.getPayload();
        System.out.println(clientMessage);
        sessions.forEach(s -> {
            try {
                s.sendMessage(new TextMessage("Hello! You session id is: " + s.getId()));
                activeSessions();
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
    }

    @Override
    public void afterConnectionEstablished(WebSocketSession session) throws Exception {
        //the messages will be broadcasted to all users.
        System.out.println("Adding new session.");
        sessions.add(session);
        System.out.println("Current session count: " + sessions.size());
    }

    @Override
    public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
        sessions.remove(session);
    }

    @Scheduled(fixedRate = 2000)
    public void activeSessions() {
        System.out.println("Total sessions: " + sessions.size());
    }
}

配置部分:

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {
    @Override
    public void registerWebSocketHandlers(@NotNull WebSocketHandlerRegistry registry) {
        registry.addHandler(new Monitoring(), "/socket");
    }
}

到期conflict描述的自定义调度程序:

@Configuration
@EnableScheduling
public class SchedulingConfig {

    // https://stackoverflow.com/questions/49343692/websocketconfigurer-and-scheduled-are-not-work-well-in-an-application

    @Bean
    public TaskScheduler taskScheduler() {
        ThreadPoolTaskScheduler taskScheduler = new ThreadPoolTaskScheduler();
        taskScheduler.setPoolSize(10);
        taskScheduler.initialize();
        return taskScheduler;
    }
}

Answer 1

您当前有 Monitoring 类的 2 个独立实例。一个由您自己创建，执行请求处理(这不是 Spring 托管 bean!)，另一个由 Spring 由于 @Configuration 检测到(这不应该是一个 @Component ？)。

删除 @Configuration 并将其替换为 @Bean 方法，这样您的 WebSocketConfig 如下所示

@Configuration
@EnableWebSocket
public class WebSocketConfig implements WebSocketConfigurer {

    @Override
    public void registerWebSocketHandlers(@NotNull WebSocketHandlerRegistry registry) {
        registry.addHandler(monitoring(), "/socket");
    }

    @Bean
    public Monitoring monitoring() {
        return new Monitoring();
    }
}

您现在拥有该 bean 的单个实例，由 Spring 管理。