尝试使用GAE数据存储中的键访问实体时出现异常

Question

我实际上正在使用GAE构建一个聊天室，问题是我将clientid和令牌存储在chatrromservlet中，并使用datastore密钥访问它们，但当我试图使用该密钥从sayservlet访问数据存储时，我得到一个异常，即没有找到具有该密钥的实体。

我的chatroomservlet

    String clientid = request.getParameter("clientid");
    ChannelService channelService = ChannelServiceFactory.getChannelService();

    String token = channelService.createChannel(clientid);
    channelService.sendMessage(new ChannelMessage(token, "Hello World"));
    System.out.println("token is ="+token);

    JSONObject job=new JSONObject();
    job.put("token",token);

    Key userkey=KeyFactory.createKey("users", "user1");
    System.out.println("user key in chatroom "+ userkey);
    Entity ent=new Entity("user");
    ent.setProperty("clientid", clientid);
    ent.setProperty("token", token);


    DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
    datastore.put(ent);
    System.out.println(ent);  

say servlet是

            String message = request.getParameter("message");
            String clientid = request.getParameter("clientid");
            System.out.println(message);

            Key userkey=KeyFactory.createKey("users", "user1");
            Entity entity;
            DatastoreService datastore = DatastoreServiceFactory
                    .getDatastoreService();
            entity = datastore.get(userkey);
            String token = (String) entity.getProperty("token");
            System.out.println("token frm db ="+token);

            ChannelService channelService = ChannelServiceFactory.getChannelService();
            channelService.sendMessage(new ChannelMessage(token, "Hello World"));
            System.out.println("message is ="+message);
            System.out.println("cid is ="+clientid);

如果在访问时有任何错误，请帮助我。

Answer 1

看起来像是在chatroomservlet中创建了一个实体，但不使用生成的密钥。因此，当您在say servlet中通过该键进行查找时，数据存储将无法找到该实体。

您的chatroomservlet应该使用userkey创建实体：

    Key userkey=KeyFactory.createKey("users", "user1");
    System.out.println("user key in chatroom "+ userkey);
    Entity ent=new Entity(userkey);