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智能协同云图库-进入编辑报错解决

问题复现

点击进入编辑，页面没变化

image.png

F12 打开控制台，两条消息，连接已建立，然后又连接已断开

image.png

后端控制台报错，LocalDataTime 没有办法序列化

image.png

因为 user 的时间字段被我改成了 LocalDateTime，而 LocalDateTime 是需要手动添加序列化器的，因为异常最终导致 WebSocket 关闭。

解决

使用 Spring 提供的 ObjectMapper 代替自己new

▼
java
复制代码
/**
 * 复用 Spring 管理的 ObjectMapper，统一支持 Long 和 LocalDateTime 序列化。
 */
@Resource
private ObjectMapper objectMapper;

image.png

▼
java
复制代码
/**
     * 将响应信息广播给 集合里的session
     *
     * @param pictureId
     * @param pictureEditResponseMessage
     * @param excludeSession
     * @throws Exception
     */
    private void broadcastToPicture(Long pictureId, PictureEditResponseMessage pictureEditResponseMessage, WebSocketSession excludeSession) throws Exception {
        Set<WebSocketSession> sessionSet = pictureSessions.get(pictureId);
        if (CollectionUtils.isEmpty(sessionSet)) {
            return;
        }

        // 使用 Spring 管理的 ObjectMapper，避免裸 ObjectMapper 无法处理 LocalDateTime。
        String message = objectMapper.writeValueAsString(pictureEditResponseMessage);

        for (WebSocketSession session : sessionSet) {
            // 排除掉 session
            if (session.equals(excludeSession)) {
                continue;
            }

            if (session.isOpen()) {
                sendTextMessage(session, message);
            }
        }
    }

    /**
     * 向当前连接发送错误消息。
     */
    public void sendErrorMessage(WebSocketSession session, User user, String errorMessage) throws Exception {
        PictureEditResponseMessage responseMessage = new PictureEditResponseMessage();
        responseMessage.setType(PictureEditMessageTypeEnum.ERROR.getValue());
        responseMessage.setMessage(errorMessage);
        if (user != null) {
            responseMessage.setUser(userService.getUserVO(user));
        }
        String message = objectMapper.writeValueAsString(responseMessage);
        sendTextMessage(session, message);
    }
    
    /**
     * WebSocketSession 不保证并发发送安全，统一同步发送。
     */
    private void sendTextMessage(WebSocketSession session, String message) throws Exception {
        if (session == null || !session.isOpen()) {
            return;
        }
        synchronized (session) {
            if (session.isOpen()) {
                session.sendMessage(new TextMessage(message));
            }
        }
    }

接收前端发来的消息，也要 使用 objectMapper 转化为对象

▼
java
复制代码
/**
     * 收到前端的信息后处理
     *
     * @param session
     * @param message
     * @throws Exception
     */
    @Override
    protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
        User user = (User) session.getAttributes().get("user");
        Long pictureId = (Long) session.getAttributes().get("pictureId");

        PictureEditRequestMessage pictureEditRequestMessage;
        try {
            // TextMessage#getPayload() 是 JSON 字符串，必须使用 JSON 反序列化。
            pictureEditRequestMessage = objectMapper.readValue(
                    message.getPayload(),
                    PictureEditRequestMessage.class
            );
        } catch (JsonProcessingException e) {
            log.warn("图片编辑消息解析失败，sessionId={}，payload={}",
                    session.getId(), message.getPayload(), e);
            sendErrorMessage(session, user, "消息格式错误");
            return;
        }

        PictureEditMessageTypeEnum messageTypeEnum =
                PictureEditMessageTypeEnum.getEnumByValue(pictureEditRequestMessage.getType());
        if (messageTypeEnum == null) {
            sendErrorMessage(session, user, "消息类型错误");
            return;
        }

        // 生产消息
        pictureEditEventProducer.publishEvent(
                pictureEditRequestMessage,
                session,
                user,
                pictureId
        );
    }

完整代码

▼
java
复制代码
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.my.picturesystembackend.manager.websocket.disruptor.PictureEditEventProducer;
import com.my.picturesystembackend.manager.websocket.model.PictureEditActionEnum;
import com.my.picturesystembackend.manager.websocket.model.PictureEditMessageTypeEnum;
import com.my.picturesystembackend.manager.websocket.model.PictureEditRequestMessage;
import com.my.picturesystembackend.manager.websocket.model.PictureEditResponseMessage;
import com.my.picturesystembackend.model.entity.User;
import com.my.picturesystembackend.service.UserService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Component;
import org.springframework.util.CollectionUtils;
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;

import javax.annotation.Resource;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

/**
* 图片编辑处理
*/
@Component
@Slf4j
public class PictureEditHandler extends TextWebSocketHandler {

  @Resource
  private UserService userService;

  @Resource
  private PictureEditEventProducer pictureEditEventProducer;

  /**
   * 复用 Spring 管理的 ObjectMapper，统一支持 Long 和 LocalDateTime 序列化。
   */
  @Resource
  private ObjectMapper objectMapper;

  // 当前正在编辑的图片的用户：key:pictureId value: 当前正在编辑的 userId
  private static final Map<Long, Long> pictureEditingUsers = new ConcurrentHashMap<>();

  // 保存连接的所有会话，key: pictureId, value: 用户会话集合
  private static final Map<Long, Set<WebSocketSession>> pictureSessions = new ConcurrentHashMap<>();

  /**
   * 连接建立成功后保存信息
   *
   * @param session
   * @throws Exception
   */
  @Override
  public void afterConnectionEstablished(WebSocketSession session) throws Exception {
      super.afterConnectionEstablished(session);

      // 保存用户信息
      User user = (User) session.getAttributes().get("user");
      Long pictureId = (Long) session.getAttributes().get("pictureId");
      // session 加到集合中
      pictureSessions.computeIfAbsent(pictureId, key -> ConcurrentHashMap.newKeySet()).add(session);
      // 发送广播信息，通知在这个集合的所有用户，who 加进来了，相当于加入房间
      PictureEditResponseMessage pictureEditResponseMessage = new PictureEditResponseMessage();
      pictureEditResponseMessage.setType(PictureEditMessageTypeEnum.INFO.getValue());
      String message = String.format("用户 %s 加入编辑", user.getUserName());
      pictureEditResponseMessage.setMessage(message);
      pictureEditResponseMessage.setUser(userService.getUserVO(user));
      // 广播消息
      broadcastToPicture(pictureId, pictureEditResponseMessage);
  }

  /**
   * 收到前端的信息后处理
   *
   * @param session
   * @param message
   * @throws Exception
   */
  @Override
  protected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception {
      User user = (User) session.getAttributes().get("user");
      Long pictureId = (Long) session.getAttributes().get("pictureId");

      PictureEditRequestMessage pictureEditRequestMessage;
      try {
          // TextMessage#getPayload() 是 JSON 字符串，必须使用 JSON 反序列化。
          pictureEditRequestMessage = objectMapper.readValue(
                  message.getPayload(),
                  PictureEditRequestMessage.class
          );
      } catch (JsonProcessingException e) {
          log.warn("图片编辑消息解析失败，sessionId={}，payload={}",
                  session.getId(), message.getPayload(), e);
          sendErrorMessage(session, user, "消息格式错误");
          return;
      }

      PictureEditMessageTypeEnum messageTypeEnum =
              PictureEditMessageTypeEnum.getEnumByValue(pictureEditRequestMessage.getType());
      if (messageTypeEnum == null) {
          sendErrorMessage(session, user, "消息类型错误");
          return;
      }

      // 生产消息
      pictureEditEventProducer.publishEvent(
              pictureEditRequestMessage,
              session,
              user,
              pictureId
      );
  }

  /**
   * 进入编辑状态
   *
   * @param pictureEditRequestMessage
   * @param session
   * @param user
   * @param pictureId
   */
  public void handleEnterEditMessage(PictureEditRequestMessage pictureEditRequestMessage, WebSocketSession session, User user, Long pictureId) throws Exception {
      // 一张图片同时只能有一个用户在编辑
      // 判断是否有其他人在编辑
      if (!pictureEditingUsers.containsKey(pictureId)) {
          // 加入编辑
          pictureEditingUsers.put(pictureId, user.getId());
          // 发送 广播 通知其他用户我已经进入编辑状态
          PictureEditResponseMessage pictureEditResponseMessage = new PictureEditResponseMessage();
          pictureEditResponseMessage.setType(PictureEditMessageTypeEnum.ENTER_EDIT.getValue());
          pictureEditResponseMessage.setMessage(String.format(" %s 开始编辑图片", user.getUserName()));
          pictureEditResponseMessage.setUser(userService.getUserVO(user));

          broadcastToPicture(pictureId, pictureEditResponseMessage);
      }
  }

  /**
   * 处理编辑动作
   *
   * @param pictureEditRequestMessage
   * @param session
   * @param user
   * @param pictureId
   */
  public void handleEditActionMessage(PictureEditRequestMessage pictureEditRequestMessage, WebSocketSession session, User user, Long pictureId) throws Exception {
      // 判断当前正在编辑的用户是不是自己
      Long currentEditUserId = pictureEditingUsers.get(pictureId);

      String editAction = pictureEditRequestMessage.getEditAction();
      PictureEditActionEnum pictureEditActionEnum = PictureEditActionEnum.getEnumByValue(editAction);
      if (pictureEditActionEnum == null) {
          return;
      }

      if (currentEditUserId != null && currentEditUserId.equals(user.getId())) {
          // 是本人发送编辑通知
          PictureEditResponseMessage pictureEditResponseMessage = new PictureEditResponseMessage();
          pictureEditResponseMessage.setType(PictureEditMessageTypeEnum.EDIT_ACTION.getValue());
          pictureEditResponseMessage.setMessage(String.format("%s 执行了 %s 操作", user.getUserName(), pictureEditActionEnum.getText()));
          pictureEditResponseMessage.setEditAction(editAction);
          pictureEditResponseMessage.setUser(userService.getUserVO(user));

          // 广播给处了自己以外的其他用户
          broadcastToPicture(pictureId, pictureEditResponseMessage, session);
      }
  }

  /**
   * 退出编辑
   *
   * @param pictureEditRequestMessage
   * @param session
   * @param user
   * @param pictureId
   */
  public void handleExitEditMessage(PictureEditRequestMessage pictureEditRequestMessage, WebSocketSession session, User user, Long pictureId) throws Exception {
      // 校验当前正在编辑的用户是不是自己
      Long currentEditUserId = pictureEditingUsers.get(pictureId);
      if (currentEditUserId != null && currentEditUserId.equals(user.getId())) {
          pictureEditingUsers.remove(pictureId);
          // 发送消息通知
          PictureEditResponseMessage pictureEditResponseMessage = new PictureEditResponseMessage();
          pictureEditResponseMessage.setType(PictureEditMessageTypeEnum.EXIT_EDIT.getValue());
          pictureEditResponseMessage.setMessage(String.format("%s 退出编辑图片", user.getUserName()));
          pictureEditResponseMessage.setUser(userService.getUserVO(user));

          broadcastToPicture(pictureId, pictureEditResponseMessage);
      }
  }

  /**
   * 关闭连接的处理
   *
   * @param session
   * @param status
   * @throws Exception
   */
  @Override
  public void afterConnectionClosed(WebSocketSession session, CloseStatus status) throws Exception {
      super.afterConnectionClosed(session, status);
      // 判断该用户是否正在编辑，如果是需要退出

      // 从 session 中获取通用参数
      User user = (User) session.getAttributes().get("user");
      Long pictureId = (Long) session.getAttributes().get("pictureId");

      handleExitEditMessage(null, session, user, pictureId);

      // 移除session
      Set<WebSocketSession> webSocketSessions = pictureSessions.get(pictureId);
      if (webSocketSessions != null) {
          webSocketSessions.remove(session);
          if (webSocketSessions.isEmpty()) {
              pictureSessions.remove(pictureId);
          }
      }

      // 发送消息退出编辑
      PictureEditResponseMessage pictureEditResponseMessage = new PictureEditResponseMessage();
      pictureEditResponseMessage.setType(PictureEditMessageTypeEnum.INFO.getValue());
      pictureEditResponseMessage.setMessage(String.format("%s离开编辑", user.getUserName()));
      pictureEditResponseMessage.setUser(userService.getUserVO(user));

      broadcastToPicture(pictureId, pictureEditResponseMessage);
  }

  /**
   * 将响应信息广播给 集合里的session
   *
   * @param pictureId
   * @param pictureEditResponseMessage
   * @param excludeSession
   * @throws Exception
   */
  private void broadcastToPicture(Long pictureId, PictureEditResponseMessage pictureEditResponseMessage, WebSocketSession excludeSession) throws Exception {
      Set<WebSocketSession> sessionSet = pictureSessions.get(pictureId);
      if (CollectionUtils.isEmpty(sessionSet)) {
          return;
      }

      // 使用 Spring 管理的 ObjectMapper，避免裸 ObjectMapper 无法处理 LocalDateTime。
      String message = objectMapper.writeValueAsString(pictureEditResponseMessage);

      for (WebSocketSession session : sessionSet) {
          // 排除掉 session
          if (session.equals(excludeSession)) {
              continue;
          }

          if (session.isOpen()) {
              sendTextMessage(session, message);
          }
      }
  }

  /**
   * 向当前连接发送错误消息。
   */
  public void sendErrorMessage(WebSocketSession session, User user, String errorMessage) throws Exception {
      PictureEditResponseMessage responseMessage = new PictureEditResponseMessage();
      responseMessage.setType(PictureEditMessageTypeEnum.ERROR.getValue());
      responseMessage.setMessage(errorMessage);
      if (user != null) {
          responseMessage.setUser(userService.getUserVO(user));
      }
      String message = objectMapper.writeValueAsString(responseMessage);
      sendTextMessage(session, message);
  }

  /**
   * WebSocketSession 不保证并发发送安全，统一同步发送。
   */
  private void sendTextMessage(WebSocketSession session, String message) throws Exception {
      if (session == null || !session.isOpen()) {
          return;
      }
      synchronized (session) {
          if (session.isOpen()) {
              session.sendMessage(new TextMessage(message));
          }
      }
  }

  /**
   * 全体广播不排除
   *
   * @param pictureId
   * @param pictureEditResponseMessage
   * @throws Exception
   */
  private void broadcastToPicture(Long pictureId, PictureEditResponseMessage pictureEditResponseMessage) throws Exception {
      broadcastToPicture(pictureId, pictureEditResponseMessage, null);
  }
}
笔记
智能协同云图库项目
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