获取AccessToken是微信接入的又一个基础操作。很多微信接口需要这个2小时一刷新的AccessToken作为参数。
首先根据开发文档把获取AccessToken需要Get的那个链接拼凑出来。
Const AccessToken = "https://api.weixin.qq.com/cgi-bin/token?grant_type=client_credential&appid=" & AppId & "&secret=" & Secret
注意这里不要使用字符串内插，因为那个不能给常量表达式用。
文档上写着返回的是Json，那就把Newtonsoft.Json装上。
然后写这个函数放到某个模块里面备用。
Public Async Function GetJsonPopulateObjectAsync(url As String, obj As Object) As Task Dim httpClient As New HttpClient httpClient.DefaultRequestHeaders.Accept.Add(New MediaTypeWithQualityHeaderValue("application/json")) Dim response = Await httpClient.GetAsync(url) If response.IsSuccessStatusCode Then Dim str = Await response.Content.ReadAsStringAsync() JsonConvert.PopulateObject(str, obj) End If End Function
接下来就是写获取数据了。AccessToken适合单实例的对象，那么我们新建模块。
用一个嵌套的类把需要反序列化的数据描述一下，并且初始化。
这里注意一下，Await是不能在SyncLock里面用的，所以要利用Monitor。
Imports System.Threading Imports System.Threading.Tasks Module AccessToken Dim dat As New Data Sub New() CreateTime = Date.Now End Sub Public Async Function GetValueAsync() As Task(Of String) Try Monitor.Enter(dat) If IsExpiredOrEmpty Then Await GetJsonFillObjectAsync(WeChatGlobalValues.AccessToken, dat) _CreateTime = Date.Now WeChatException.Assert(dat.errcode) End If Return dat.access_token Finally Monitor.Exit(dat) End Try End Function Public ReadOnly Property CreateTime As Date Public ReadOnly Property IsExpiredOrEmpty As Boolean Get Return Date.Now >= CreateTime.AddSeconds(dat.expires_in) End Get End Property Private Class Data Public Property access_token$ Public Property expires_in% = -1 Public Property errcode% Public Property errmsg$ End Class End Module
如果出错，微信会产生错误码。根据错误码表编写异常类
Public Class WeChatException Inherits Exception Public ReadOnly Property ErrorCode% Sub New() MyBase.New("调用微信服务时发生异常") End Sub Sub New(ErrorCode%) MyBase.New(ErrorMap(ErrorCode)) _ErrorCode = ErrorCode End Sub ‘‘‘ <summary> ‘‘‘ 断言这个错误码并不代表出错。如果断言失败则抛出异常。 ‘‘‘ </summary> ‘‘‘ <param name="ErrorCode%">错误码</param> Public Shared Sub Assert(ErrorCode%) If ErrorCode <> 0 Then Throw New WeChatException(ErrorCode) End Sub Shared ErrorMap As New Dictionary(Of Integer, String) From { {-1, "系统繁忙，此时请开发者稍候再试"}, {0, "请求成功"}, {40001, "获取access_token时AppSecret错误，或者access_token无效。请开发者认真比对AppSecret的正确性，或查看是否正在为恰当的公众号调用接口"}, {40002, "不合法的凭证类型"}, {40003, "不合法的OpenID，请开发者确认OpenID（该用户）是否已关注公众号，或是否是其他公众号的OpenID"}, {40004, "不合法的媒体文件类型"}, {40005, "不合法的文件类型"}, {40006, "不合法的文件大小"}, {40007, "不合法的媒体文件id"}, {40008, "不合法的消息类型"}, {40009, "不合法的图片文件大小"}, {40010, "不合法的语音文件大小"}, {40011, "不合法的视频文件大小"}, {40012, "不合法的缩略图文件大小"}, {40013, "不合法的AppID，请开发者检查AppID的正确性，避免异常字符，注意大小写"}, {40014, "不合法的access_token，请开发者认真比对access_token的有效性（如是否过期），或查看是否正在为恰当的公众号调用接口"}, {40015, "不合法的菜单类型"}, {40016, "不合法的按钮个数"}, {40017, "不合法的按钮个数"}, {40018, "不合法的按钮名字长度"}, {40019, "不合法的按钮KEY长度"}, {40020, "不合法的按钮URL长度"}, {40021, "不合法的菜单版本号"}, {40022, "不合法的子菜单级数"}, {40023, "不合法的子菜单按钮个数"}, {40024, "不合法的子菜单按钮类型"}, {40025, "不合法的子菜单按钮名字长度"}, {40026, "不合法的子菜单按钮KEY长度"}, {40027, "不合法的子菜单按钮URL长度"}, {40028, "不合法的自定义菜单使用用户"}, {40029, "不合法的oauth_code"}, {40030, "不合法的refresh_token"}, {40031, "不合法的openid列表"}, {40032, "不合法的openid列表长度"}, {40033, "不合法的请求字符，不能包含\uxxxx格式的字符"}, {40035, "不合法的参数"}, {40038, "不合法的请求格式"}, {40039, "不合法的URL长度"}, {40050, "不合法的分组id"}, {40051, "分组名字不合法"}, {40117, "分组名字不合法"}, {40118, "media_id大小不合法"}, {40119, "button类型错误"}, {40120, "button类型错误"}, {40121, "不合法的media_id类型"}, {40132, "微信号不合法"}, {40137, "不支持的图片格式"}, {41001, "缺少access_token参数"}, {41002, "缺少appid参数"}, {41003, "缺少refresh_token参数"}, {41004, "缺少secret参数"}, {41005, "缺少多媒体文件数据"}, {41006, "缺少media_id参数"}, {41007, "缺少子菜单数据"}, {41008, "缺少oauth code"}, {41009, "缺少openid"}, {42001, "access_token超时，请检查access_token的有效期，请参考基础支持-获取access_token中，对access_token的详细机制说明"}, {42002, "refresh_token超时"}, {42003, "oauth_code超时"}, {43001, "需要GET请求"}, {43002, "需要POST请求"}, {43003, "需要HTTPS请求"}, {43004, "需要接收者关注"}, {43005, "需要好友关系"}, {44001, "多媒体文件为空"}, {44002, "POST的数据包为空"}, {44003, "图文消息内容为空"}, {44004, "文本消息内容为空"}, {45001, "多媒体文件大小超过限制"}, {45002, "消息内容超过限制"}, {45003, "标题字段超过限制"}, {45004, "描述字段超过限制"}, {45005, "链接字段超过限制"}, {45006, "图片链接字段超过限制"}, {45007, "语音播放时间超过限制"}, {45008, "图文消息超过限制"}, {45009, "接口调用超过限制"}, {45010, "创建菜单个数超过限制"}, {45015, "回复时间超过限制"}, {45016, "系统分组，不允许修改"}, {45017, "分组名字过长"}, {45018, "分组数量超过上限"}, {46001, "不存在媒体数据"}, {46002, "不存在的菜单版本"}, {46003, "不存在的菜单数据"}, {46004, "不存在的用户"}, {47001, "解析JSON/XML内容错误"}, {48001, "api功能未授权，请确认公众号已获得该接口，可以在公众平台官网-开发者中心页中查看接口权限"}, {50001, "用户未授权该api"}, {50002, "用户受限，可能是违规后接口被封禁"}, {61451, "参数错误(invalid parameter)"}, {61452, "无效客服账号(invalid kf_account)"}, {61453, "客服帐号已存在(kf_account exsited)"}, {61454, "客服帐号名长度超过限制(仅允许10个英文字符，不包括@及@后的公众号的微信号)(invalid kf_acount length)"}, {61455, "客服帐号名包含非法字符(仅允许英文+数字)(illegal character in kf_account)"}, {61456, "客服帐号个数超过限制(10个客服账号)(kf_account count exceeded)"}, {61457, "无效头像文件类型(invalid file type)"}, {61450, "系统错误(system error)"}, {61500, "日期格式错误"}, {61501, "日期范围错误"}, {9001001, "POST数据参数不合法"}, {9001002, "远端服务不可用"}, {9001003, "Ticket不合法"}, {9001004, "获取摇周边用户信息失败"}, {9001005, "获取商户信息失败"}, {9001006, "获取OpenID失败"}, {9001007, "上传文件缺失"}, {9001008, "上传素材的文件类型不合法"}, {9001009, "上传素材的文件尺寸不合法"}, {9001010, "上传失败"}, {9001020, "帐号不合法"}, {9001021, "已有设备激活率低于50%，不能新增设备"}, {9001022, "设备申请数不合法，必须为大于0的数字"}, {9001023, "已存在审核中的设备ID申请"}, {9001024, "一次查询设备ID数量不能超过50"}, {9001025, "设备ID不合法"}, {9001026, "页面ID不合法"}, {9001027, "页面参数不合法"}, {9001028, "一次删除页面ID数量不能超过10"}, {9001029, "页面已应用在设备中，请先解除应用关系再删除"}, {9001030, "一次查询页面ID数量不能超过50"}, {9001031, "时间区间不合法"}, {9001032, "保存设备与页面的绑定关系参数错误"}, {9001033, "门店ID不合法"}, {9001034, "设备备注信息过长"}, {9001035, "设备申请参数不合法"}, {9001036, "查询起始值begin不合法"} } End Class