.netcore2.1 JS-SDK 从后台获取微信签名，实现自定义分享标题、描述、图片

　　最近项目移动端需要实现微信自定义分享功能，包含分享自定义标题、描述等。

首先到公众号的后台，功能设置里面，添加将要被分享的域名，如图

后端签名算法实现，参考腾讯开发者文档https://mp.weixin.qq.com/wiki?t=resource/res_main&id=mp1421141115

　　jsapi_ticket

　　生成签名之前必须先了解一下jsapi_ticket，jsapi_ticket是公众号用于调用微信JS接口的临时票据。正常情况下，jsapi_ticket的有效期为7200秒，通过access_token来获取。由于获取jsapi_ticket的api调用次数非常有限，频繁刷新jsapi_ticket会导致api调用受限，影响自身业务，开发者必须在自己的服务全局缓存jsapi_ticket 。

　　生成签名步骤，获取AccessToken-》获取JsApiTicket-》生成签名

　　appsettings配置文件添加配置

 "Api": {

    "JSJDKBaseApi": "https://api.weixin.qq.com/cgi-bin"

  },

  "JSJDK": {

    "AppId": "***",

    "Secret": "****"

  }

创建签名公用类

 public class JSSDKSignHelper

    {

        private static AccessTokenResponse singleAccessToken;

        private  string _tencentApi { get; set; }

        private  string _appid { get; set; }

        private  string _appSecret { get; set; }

        public  JSSDKSignHelper(IConfiguration config)

        {

            _tencentApi = config["Api:JSJDKBaseApi"];

            _appid = config["JSJDK:AppId"];

            _appSecret = config["JSJDK:Secret"];

        }

        public string GetAccessTokenSingle(out bool isNewObj)

        {

            isNewObj = false;

            if (singleAccessToken != null && (singleAccessToken.expire_out > DateTime.Now.AddHours()))

            {

                return singleAccessToken.access_token;

            }

            else

            {

                var response = GetAccessToken();

                if (response.errcode == )

                {

                    response.expire_out = DateTime.Now.AddHours(expireHour);

                    singleAccessToken = response;

                    isNewObj = true;

                    return response?.access_token;

                }

            }

            return null;

        }

        /// <summary>

        /// 获取access_token

        /// </summary>

        /// <returns></returns>

        private AccessTokenResponse GetAccessToken()

        {

            string url = _tencentApi + "/token?grant_type=client_credential&appid=" + _appid + "&secret=" + _appSecret;

            var response = ApiClient.GetJson<AccessTokenResponse>(url);

            return response;

        }

        /// <summary>

        /// 获取JsApiTicket

        /// </summary>

        /// <param name="accessToken"></param>

        /// <returns></returns>

        public  string GetJsApiTicket(string accessToken)

        {

            if (string.IsNullOrWhiteSpace(accessToken))

            {

                return null;

            }

            string url = _tencentApi + $"/ticket/getticket?type=jsapi&access_token={accessToken}";

            var response = ApiClient.GetJson<AccessTicketResponse>(url);

            return response?.ticket;

        }

        /// <summary>

        /// 获取签名

        /// </summary>

        /// <param name="jsapi_ticket"></param>

        /// <param name="noncestr">随机字符串(必须与wx.config中的nonceStr相同)</param>

        /// <param name="timestamp">时间戳(必须与wx.config中的timestamp相同)</param>

        /// <param name="url">当前网页的URL，不包含#及其后面部分(必须是调用JS接口页面的完整URL)</param>

        /// <returns></returns>

        public string  GetSignature(string jsapi_ticket, string noncestr, string timestamp, string url)

        {

            if (string.IsNullOrEmpty(jsapi_ticket) || string.IsNullOrEmpty(noncestr) || string.IsNullOrEmpty(timestamp) || string.IsNullOrEmpty(url))

                return null;

            var string1Builder = new StringBuilder();

            string1Builder.Append("jsapi_ticket=").Append(jsapi_ticket).Append("&")

                          .Append("noncestr=").Append(noncestr).Append("&")

                          .Append("timestamp=").Append(timestamp).Append("&")

                          .Append("url=").Append(url.IndexOf("#") >=  ? url.Substring(, url.IndexOf("#")) : url);

             return Sha1Sign(string1Builder.ToString());

        }

        /// <summary>

        /// Sha1加密签名

        /// </summary>

        /// <param name="str"></param>

        /// <returns></returns>

        public string Sha1Sign(string str)

        {

            SHA1 sha1 = new SHA1CryptoServiceProvider();

            byte[] bytes_sha1_in = System.Text.UTF8Encoding.Default.GetBytes(str);

            byte[] bytes_sha1_out = sha1.ComputeHash(bytes_sha1_in);

            string signature = BitConverter.ToString(bytes_sha1_out);

            signature = signature.Replace("-", "").ToLower();

            return signature;

        }

    }

签名定义的Model

public class AccessTokenResponse: BaseResponse

    {

        /// <summary>

        /// 返回access_token值，有效期7200秒

        /// </summary>

        public string access_token { get; set; }

        /// <summary>

        /// 过期时间，单位小时

        /// </summary>

        public DateTime expire_out { get; set; }

    }

    public class AccessTicketResponse : BaseResponse

    {

        /// <summary>

        /// 返回Ticket票据，有效期7200秒

        /// </summary>

        public string ticket { get; set; }

    }

  public class BaseResponse

    {

        /// <summary>

        /// 过期时间，单位秒

        /// </summary>

        public string expire_in { get; set; }

        /// <summary>

        /// 错误代码

        /// </summary>

        public Int32 errcode { get; set; }

        /// <summary>

        /// 错误信息描述

        /// </summary>

        public string errmsg { get; set; }

    }

创建生成签名的时间戳和随机串

 /// <summary>

        /// 获取微信JS-JDK时间戳

        /// </summary>

        /// <returns></returns>

        public static string GetTimeStamp()

        {

            TimeSpan ts = DateTime.UtcNow - new DateTime(, , , , , );

            return Convert.ToInt64(ts.TotalSeconds).ToString();

        }

        /// <summary>

        /// JS-JDK 创建随机字符串

        /// </summary>

        /// <returns></returns>

        public static string CreatenNonce_str()

        {

            Random r = new Random();

            var sb = new StringBuilder();

            var length = strs.Length;

            for (int i = ; i < ; i++)

            {

                sb.Append(strs[r.Next(length - )]);

            }

            return sb.ToString();

        }

Action中实际调用

        [HttpPost]

        [Route("GetSignature")]

        public string GetSignature(string url= "http://www.sina.cn/")

        {

            try

            {

                if (string.IsNullOrEmpty(url)) return "url不能为空";

                string _jsTicket = null, _signature = null;

                string _accessToken = _jsSignHelper.GetAccessTokenSingle(out bool isNewObj);

                WxConfigModel model = new WxConfigModel();

                model.AppId = appId;

                model.TimeStamp = MyUtil.GetTimeStamp();

                model.NonceStr = MyUtil.CreatenNonce_str();

                if (isNewObj|| _wxConfigModel.Signature==null)

                {

                    _jsTicket = _jsSignHelper.GetJsApiTicket(_accessToken);

                    _signature = _jsSignHelper.GetSignature(_jsTicket, model.NonceStr, model.TimeStamp, url);

                    model.jsTicket = _jsTicket;

                    model.Signature = _signature;

                    _wxConfigModel = model;

                }

                return JsonConvert.SerializeObject(model);

            }

            catch (Exception ex)

            {

                throw ex;

            }

        }

　　注意：

签名用的noncestr和timestamp必须与wx.config中的nonceStr和timestamp相同。
移动端分享时，不能本地测试，需要发布到外网测试，否则报签名错误
生成的签名，可以实用校验工具校验是否正确。https://mp.weixin.qq.com/debug/cgi-bin/sandbox?t=jsapisign

巴特西

.netcore2.1 JS-SDK 从后台获取微信签名，实现自定义分享标题、描述、图片

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