Question

我正在为我的应用程序使用简单的聊天模块，使用Spring WebFlux和后端的ReactiveMongoRepository以及前面的Angular 4。我能够通过WebSocketSession接收数据，但在从db传输所有消息后，我想保持连接，以便我可以更新消息列表。任何人都可以给我提供如何实现这一点的线索，或者我可能会遵循错误的假设吗？

Java Backend负责WebSocket，我的订阅者只记录当前状态，与此无关：

WebFluxConfiguration：

@Configuration
@EnableWebFlux
public class WebSocketConfig {

private final WebSocketHandler webSocketHandler;

@Autowired
public WebSocketConfig(WebSocketHandler webSocketHandler) {
    this.webSocketHandler = webSocketHandler;
}

@Bean
@Primary
public HandlerMapping webSocketMapping() {
    Map<String, Object> map = new HashMap<>();
    map.put("/websocket-messages", webSocketHandler);

    SimpleUrlHandlerMapping mapping = new SimpleUrlHandlerMapping();
    mapping.setOrder(10);
    mapping.setUrlMap(map);
    return mapping;
}

@Bean
public WebSocketHandlerAdapter handlerAdapter() {
    return new WebSocketHandlerAdapter();
}


}

WebSocketHandler实现

@Component
public class MessageWebSocketHandler implements WebSocketHandler {

private final MessageRepository messageRepository;
private ObjectMapper mapper = new ObjectMapper();
private MessageSubscriber subscriber = new MessageSubscriber();

@Autowired
public MessageWebSocketHandler(MessageRepository messageRepository) {
    this.messageRepository = messageRepository;
}

@Override
    public Mono<Void> handle(WebSocketSession session) {
    session.receive()
            .map(WebSocketMessage::getPayloadAsText)
            .map(this::toMessage)
            .subscribe(subscriber::onNext, subscriber:: onError, subscriber::onComplete);
    return session.send(
            messageRepository.findAll()
                    .map(this::toJSON)
                    .map(session::textMessage));
}

private String toJSON(Message message) {
    try {
        return mapper.writeValueAsString(message);
    } catch (JsonProcessingException e) {
        throw new RuntimeException(e);
    }
}

private Message toMessage(String json) {
    try {
        return mapper.readValue(json, Message.class);
    } catch (IOException e) {
        throw new RuntimeException("Invalid JSON:" + json, e);
    }
}
}

和MongoRepo

@Repository
public interface MessageRepository extends 
ReactiveMongoRepository<Message,String> {
}

前端处理：

@Injectable()
export class WebSocketService {
  private subject: Rx.Subject<MessageEvent>;

  constructor() {
  }

  public connect(url): Rx.Subject<MessageEvent> {
    if (!this.subject) {
      this.subject = this.create(url);
      console.log('Successfully connected: ' + url);
    }
    return this.subject;
  }

  private create(url): Rx.Subject<MessageEvent> {
    const ws = new WebSocket(url);
    const observable = Rx.Observable.create(
      (obs: Rx.Observer<MessageEvent>) => {
        ws.onmessage = obs.next.bind(obs);
        ws.onerror = obs.error.bind(obs);
        ws.onclose = obs.complete.bind(obs);
        return ws.close.bind(ws);
      });
    const observer = {
      next: (data: Object) => {
        if (ws.readyState === WebSocket.OPEN) {
          ws.send(JSON.stringify(data));
        }
      }
    };
    return Rx.Subject.create(observer, observable);
  }
}

在其他服务中我将observable从响应映射到我的类型

  constructor(private wsService: WebSocketService) {
    this.messages = <Subject<MessageEntity>>this.wsService
      .connect('ws://localhost:8081/websocket-messages')
      .map((response: MessageEvent): MessageEntity => {
        const data = JSON.parse(response.data);
        return new MessageEntity(data.id, data.user_id, data.username, data.message, data.links);
      });
  }

最后订阅了send函数，由于关闭连接我无法使用：

  ngOnInit() {
    this.messages = [];
    this._ws_subscription = this.chatService.messages.subscribe(
      (message: MessageEntity) => {
        this.messages.push(message);
      },
      error2 => {
        console.log(error2.json());
      },
      () => {
        console.log('Closed');
      }
    );
  }

  sendTestMessage() {
    this.chatService.messages.next(new MessageEntity(null, '59ca30ac87e77d0f38237739', 'mickl', 'test message angular', null));
  }

Answer 1

假设您的聊天消息在收到时被持久保存到数据存储区，您可以使用Spring Data MongoDB Reactive中的tailable游标功能（请参阅reference documentation）。

因此，您可以在存储库中创建一个新方法，如：

public interface MessageRepository extends ReactiveSortingRepository< Message, String> {

    @Tailable
    Flux<Message> findWithTailableCursor();
}

请注意，tailable游标有一些限制：您需要对mongo集合进行限制，并按照插入顺序对条目进行流式处理。

Spring WebFlux websocket支持尚不支持STOMP和消息代理，但对于这样的用例，这可能是更好的选择。

Spring WebFlux反应式WebSocket阻止连接关闭

1 个答案: