WeChat development of receiving event push and message deduplication

As mentioned in the previous blog post, WeChat messages can be roughly divided into two types. One is ordinary messages including text, voice, pictures, etc., and the other is the event type to be described in this article. . Including: following/unfollowing events, scanning QR code events with parameters, reporting geographical location events, custom menu-related events, etc. This article explains them one by one.

As mentioned in the previous article, If the WeChat server does not receive a response within 5 seconds, it will disconnect the connection and reinitiate the request, retrying three times in total. In this case, the problem arises. There is such a scenario: when a user follows a WeChat account, the current user information is obtained, and then the information is written to the database. Similar to registration on PC website. Perhaps because of this concern, the business logic we need to handle is relatively complex. Such as sending points, writing user logs, and assigning user groups. Wait... A series of logic needs to be executed, or the network environment is relatively complex and there is no guarantee that the current user's operation will be responded to within 5 seconds. Then if the operation is not completed yet, the WeChat server pushes the same attention event to our server. We will execute our logic again, which may lead to duplicate data in the database (some children's shoes will say, I first determine whether it already exists before inserting data, if it exists The insertion operation will not be performed. What I want to say is that I thought so at the beginning, but there is still a gap between the real operating environment and our debugging environment. Until I found that there was a lot of duplicate user information in the database, I Only then did I realize the importance of message deduplication).

Deduplication of messages There is a difference between ordinary messages and event messages. Ordinary messages use msgid, while event messages use FromUserName + CreateTime. My idea is:

1. Create a new class BaseMsg with three attributes namely FromUser, MsgFlag, and CreateTime. The code is as follows:

2. public class BaseMsg
       {        /// <summary>
           /// 发送者标识        /// </summary>
           public string FromUser { get; set; }        /// <summary>
           /// 消息表示。普通消息时，为msgid，事件消息时，为事件的创建时间        /// </summary>
           public string MsgFlag { get; set; }        /// <summary>
           /// 添加到队列的时间        /// </summary>
           public DateTime CreateTime { get; set; }
       }

3. Create a staticlist_queue to store the message list. The type of the list is Listf822bda892e76d613fb5d807a4e9e7c8.

4. Before processing the WeChat message body, first determine whether the list is instantiated. If not, instantiate it. Otherwise, determine whether the length of the list is greater than or equal to 50 (this can be customized, The purpose is the number of concurrent messages on WeChat). If it is greater than or equal to 50, messages that have not responded within 20 seconds will be retained (retry once every 5 seconds, a total of 3 retries, which is 15 seconds. To be on the safe side, write 20 seconds here).

5. Get the message type of the current message body and determine whether the current message has been requested based on _queue. If it is an event, FromUser and creation time are saved. If it is a normal message, MsgFlag is saved. The following is the code:

if (_queue == null)
            {
                _queue = new List<BaseMsg>();
            }            else if(_queue.Count>=50)
            {
                _queue = _queue.Where(q => { return q.CreateTime.AddSeconds(20) > DateTime.Now; }).ToList();//保留20秒内未响应的消息            }
            XElement xdoc = XElement.Parse(xml);            var msgtype = xdoc.Element("MsgType").Value.ToUpper();            var FromUserName = xdoc.Element("FromUserName").Value;            var MsgId = xdoc.Element("MsgId").Value;            var CreateTime = xdoc.Element("CreateTime").Value;
            MsgType type = (MsgType)Enum.Parse(typeof(MsgType), msgtype);            if (type!=MsgType.EVENT)
            {                if (_queue.FirstOrDefault(m => { return m.MsgFlag == MsgId; }) == null)
                {
                    _queue.Add(new BaseMsg
                    {
                        CreateTime = DateTime.Now,
                        FromUser = FromUserName,
                        MsgFlag = MsgId
                    });
                }                else
                {                    return null;
                }
               
            }            else
            {                if (_queue.FirstOrDefault(m => { return m.MsgFlag == CreateTime; }) == null)
                {
                    _queue.Add(new BaseMsg
                    {
                        CreateTime = DateTime.Now,
                        FromUser = FromUserName,
                        MsgFlag = CreateTime
                    });
                }                else
                {                    return null;
                }
            }

When the message already exists in the queue, the current message will not be converted into an entity, and null will be returned directly. When calling, it will not be done when null is returned. Any processing.

Let’s start with the event message. Continuing from the previous article. All messages inherit BaseMessage, and all event types contain an Event property. For the convenience of calling, the message type is defined as an enumeration. The code is as follows:

/// <summary>
    /// 事件类型枚举    /// </summary>
    public enum Event
    {        /// <summary>
        /// 非事件类型        /// </summary>        NOEVENT,        /// <summary>
        /// 订阅        /// </summary>        SUBSCRIBE,        /// <summary>
        /// 取消订阅        /// </summary>        UNSUBSCRIBE,        /// <summary>
        /// 扫描带参数的二维码        /// </summary>        SCAN,        /// <summary>
        /// 地理位置        /// </summary>        LOCATION,        /// <summary>
        /// 单击按钮        /// </summary>        CLICK,        /// <summary>
        /// 链接按钮        /// </summary>        VIEW,        /// <summary>
        /// 扫码推事件        /// </summary>        SCANCODE_PUSH,        /// <summary>
        /// 扫码推事件且弹出“消息接收中”提示框        /// </summary>        SCANCODE_WAITMSG,        /// <summary>
        /// 弹出系统拍照发图        /// </summary>        PIC_SYSPHOTO,        /// <summary>
        /// 弹出拍照或者相册发图        /// </summary>        PIC_PHOTO_OR_ALBUM,        /// <summary>
        /// 弹出微信相册发图器        /// </summary>        PIC_WEIXIN,        /// <summary>
        /// 弹出地理位置选择器        /// </summary>        LOCATION_SELECT,        /// <summary>
        /// 模板消息推送        /// </summary>        TEMPLATESENDJOBFINISH
    }

After defining the enumeration, it is time to define the message entity.

Follow/unfollow event

xml data package is as follows:

<xml><ToUserName><![CDATA[toUser]]></ToUserName><FromUserName><![CDATA[FromUser]]></FromUserName><CreateTime>123456789</CreateTime><MsgType><![CDATA[event]]></MsgType><Event><![CDATA[subscribe]]></Event></xml>

Corresponding entity:

/// <summary>
    /// 订阅/取消订阅事件    /// </summary>
    public class SubEventMessage : EventMessage
    {        private string _eventkey;        /// <summary>
        /// 事件KEY值，qrscene_为前缀，后面为二维码的参数值（已去掉前缀，可以直接使用）        /// </summary>
        public string EventKey
        {            get { return _eventkey; }            set { _eventkey = value.Replace("qrscene_", ""); }
        }        /// <summary>
        /// 二维码的ticket，可用来换取二维码图片        /// </summary>
        public string Ticket { get; set; }

    }

What needs to be noted here Yes, when the user scans the QR code with parameters, if the user does not follow the current official account, when the user follows it, the qrscene_ parameter and Ticket will be included in the message body, so two attributes are defined here: EventKey, Ticket . When assigning a value to EventKey, replace qrscene_, because what we really need is the following parameters.

Scan QR code event with parameters

When a user scans a QR code with scene value, two events may be pushed:

1. If the user has not followed the official account, the user can follow the official account. After following the official account, WeChat will push the follow event with the scene value to the developer.

2. If the user has followed the official account, WeChat will push the scanning event with scene value to the developer. ,

The first type has been discussed above, and only the second type will be explained here.

Event push when the user has followed

The xml package is as follows:

<xml><ToUserName><![CDATA[toUser]]></ToUserName><FromUserName><![CDATA[FromUser]]></FromUserName><CreateTime>123456789</CreateTime><MsgType><![CDATA[event]]></MsgType><Event><![CDATA[SCAN]]></Event><EventKey><![CDATA[SCENE_VALUE]]></EventKey><Ticket><![CDATA[TICKET]]></Ticket></xml>

The corresponding entity is as follows:

/// <summary>
    /// 扫描带参数的二维码实体    /// </summary>
    public class ScanEventMessage : EventMessage
    {        /// <summary>
        /// 事件KEY值，是一个32位无符号整数，即创建二维码时的二维码scene_id        /// </summary>
        public string EventKey { get; set; }        /// <summary>
        /// 二维码的ticket，可用来换取二维码图片        /// </summary>
        public string Ticket { get; set; }

    }

Reporting geographical location events

When the official account turns on the geographical location reporting function, every time when entering the official account session, after the user agrees to report the geographical location, it will be reported when entering. The geographical location, or the geographical location is reported every 5 seconds after entering the reply. The official account can modify the settings in the background of the official platform. When reporting the geographical location, WeChat will push the reported geographical location event to the URL filled in by the developer.

xml data package is as follows:

<xml><ToUserName><![CDATA[toUser]]></ToUserName><FromUserName><![CDATA[fromUser]]></FromUserName><CreateTime>123456789</CreateTime><MsgType><![CDATA[event]]></MsgType><Event><![CDATA[LOCATION]]></Event><Latitude>23.137466</Latitude><Longitude>113.352425</Longitude><Precision>119.385040</Precision></xml>

The corresponding entity is as follows:

/// <summary>
    /// 上报地理位置实体    /// </summary>
    public class LocationEventMessage : EventMessage
    {        /// <summary>
        /// 地理位置纬度        /// </summary>
        public string Latitude { get; set; }        /// <summary>
        /// 地理位置经度        /// </summary>
        public string Longitude { get; set; }       /// <summary>
        /// 地理位置精度       /// </summary>
        public string Precision { get; set; }

    }

自定义菜单事件常用的事件有：click，view，scancode_puth，scancode_waitmsg，location_select。另外还有三种发图的事件，由于并不常用，笔者也没想到使用场景，再次就不一一讲述了，有兴趣的可以自己研究下，或者和我进行交流。

click事件推送的xml数据包：

<xml><ToUserName><![CDATA[toUser]]></ToUserName><FromUserName><![CDATA[FromUser]]></FromUserName><CreateTime>123456789</CreateTime><MsgType><![CDATA[event]]></MsgType><Event><![CDATA[CLICK]]></Event><EventKey><![CDATA[EVENTKEY]]></EventKey></xml>

view事件推送的xml数据包和click的格式是一样的，所以定义一个类就可以了，如下：

/// <summary>
    /// 普通菜单事件，包括click和view    /// </summary>
    public class NormalMenuEventMessage : EventMessage
    {        /// <summary>
        /// 事件KEY值，设置的跳转URL        /// </summary>
        public string EventKey { get; set; }
  

    }

scancode事件的xml数据包如下：

<xml><ToUserName><![CDATA[ToUserName]]></ToUserName><FromUserName><![CDATA[FromUserName]]></FromUserName><CreateTime>1419265698</CreateTime><MsgType><![CDATA[event]]></MsgType><Event><![CDATA[scancode_push]]></Event><EventKey><![CDATA[EventKey]]></EventKey><ScanCodeInfo><ScanType><![CDATA[qrcode]]></ScanType><ScanResult><![CDATA[http://weixin.qq.com/r/JEy5oRLE0U_urVbC9xk2]]></ScanResult></ScanCodeInfo></xml>

对应的实体如下：

/// <summary>
    /// 菜单扫描事件    /// </summary>
    public class ScanMenuEventMessage : EventMessage
    {        /// <summary>
        /// 事件KEY值        /// </summary>
        public string EventKey { get; set; }        /// <summary>
        /// 扫码类型。qrcode是二维码，其他的是条码        /// </summary>
        public string ScanType { get; set; }        /// <summary>
        /// 扫描结果        /// </summary>
        public string ScanResult { get; set; }
    }

至此，当前常用的事件类型消息都已定义完毕，结合上一篇所讲的，将xml数据包转换成对象的完整代码如下：

public class MessageFactory
    {        private static List _queue; 
        public static BaseMessage CreateMessage(string xml)
        {            if (_queue == null)
            {
                _queue = new List<BaseMsg>();
            }            else if(_queue.Count>=50)
            {
                _queue = _queue.Where(q => { return q.CreateTime.AddSeconds(20) > DateTime.Now; }).ToList();//保留20秒内未响应的消息            }
            XElement xdoc = XElement.Parse(xml);            var msgtype = xdoc.Element("MsgType").Value.ToUpper();            var FromUserName = xdoc.Element("FromUserName").Value;            var MsgId = xdoc.Element("MsgId").Value;            var CreateTime = xdoc.Element("CreateTime").Value;
            MsgType type = (MsgType)Enum.Parse(typeof(MsgType), msgtype);            if (type!=MsgType.EVENT)
            {                if (_queue.FirstOrDefault(m => { return m.MsgFlag == MsgId; }) == null)
                {
                    _queue.Add(new BaseMsg
                    {
                        CreateTime = DateTime.Now,
                        FromUser = FromUserName,
                        MsgFlag = MsgId
                    });
                }                else
                {                    return null;
                }
               
            }            else
            {                if (_queue.FirstOrDefault(m => { return m.MsgFlag == CreateTime; }) == null)
                {
                    _queue.Add(new BaseMsg
                    {
                        CreateTime = DateTime.Now,
                        FromUser = FromUserName,
                        MsgFlag = CreateTime
                    });
                }                else
                {                    return null;
                }
            }            switch (type)
            {                case MsgType.TEXT: return Utils.ConvertObj(xml);                case MsgType.IMAGE: return Utils.ConvertObj(xml);                case MsgType.VIDEO: return Utils.ConvertObj(xml);                case MsgType.VOICE: return Utils.ConvertObj(xml);                case MsgType.LINK:                    return Utils.ConvertObj(xml);                case MsgType.LOCATION:                    return Utils.ConvertObj(xml);                case MsgType.EVENT://事件类型                {                    var eventtype = (Event)Enum.Parse(typeof(Event), xdoc.Element("Event").Value.ToUpper());                    switch (eventtype)
                    {                        case Event.CLICK:                            return Utils.ConvertObj(xml);                        case Event.VIEW: return Utils.ConvertObj(xml);                        case Event.LOCATION: return Utils.ConvertObj(xml);                        case Event.LOCATION_SELECT: return Utils.ConvertObj(xml);                        case Event.SCAN: return Utils.ConvertObj(xml);                        case Event.SUBSCRIBE: return Utils.ConvertObj(xml);                        case Event.UNSUBSCRIBE: return Utils.ConvertObj(xml);                        case Event.SCANCODE_WAITMSG: return Utils.ConvertObj(xml);                        default:                            return Utils.ConvertObj(xml);
                    }
                } break;                default:                    return Utils.ConvertObj(xml);
            }
        }
    }

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