前言

製作 API 前必須先到 Google Cloud API 完成註冊，過程中會比較繁雜內容請參閱即可。

Google Cloud API

創建憑證

選擇 OAuth 用戶端 ID 。如果不確定授權 URL 可以先跳過。


創建專案

架構需要驗證 OAuth2 先確認要設定 “重新導向 URI”，範例使用 https://localhost:999/Api/Google/Home 。

一、取得URL

Redirect URL 從 Youtube API 官方網文件可以找得到，原則上直接使用下圖位置的 URL 即可。參數傳值部分官方已經有提供使用方式，因為他有特定傳參數

二、AppSetting.json

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{
    "Google": {
    "Oauth": {
      "url": "https://accounts.google.com/o/oauth2/v2/auth",
      "scope": "https://www.googleapis.com/auth/youtube",
      "access_type": "offline",
      "include_granted_scopes": "true",
      "state": "state_parameter_passthrough_value",
      "redirect_uri": "https://localhost:999/Api/Google/Home",
      "response_type": "code",
      "client_id": "client_id",
      "client_secret": "client_secret"
    }
  }
}

製作授權網址

使用 https://localhost:999/Api/Google/Home 網址，必須要確認使用者是否已經是授權登入。

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[HttpGet("Home")]
 public async Task<IActionResult> Home([FromQuery] string code)
 {
     if (string.IsNullOrEmpty(code)) return this.StatusCode(400);

     string accessToken = await this.ExchangeAccessToken(code);
     if (string.IsNullOrEmpty(accessToken))
     {
         return this.StatusCode(400);
     }

     var claims = new List<Claim>
     {
         new Claim("access_token",accessToken ),
         new Claim(ClaimTypes.Role, "nobody"),
     };

     var claimsIdentity = new ClaimsIdentity(
         claims, CookieAuthenticationDefaults.AuthenticationScheme);

     HttpContext.SignInAsync(
         CookieAuthenticationDefaults.AuthenticationScheme,
         new ClaimsPrincipal(claimsIdentity),
         authProperties);
     return this.Redirect("/");
 }

 private async Task<string> ExchangeAccessToken(string code)
 {
     //取得當前 html 字串
     HttpClient client = new();
     client
         .DefaultRequestHeaders
         .Accept
         .Add(
             new MediaTypeWithQualityHeaderValue("text/json")
         );//ACCEPT header
     var request = new HttpRequestMessage(HttpMethod.Post, "https://oauth2.googleapis.com/token");

     request.Content = new FormUrlEncodedContent(
         new Dictionary<string, string>
         {
             ["grant_type"] = "authorization_code",
             ["code"] = code,
             ["redirect_uri"] = Config.GetConfiguration().GetValue<string>("Google:Oauth:redirect_uri").ToString(),
             ["client_id"] = Config.GetConfiguration().GetValue<string>("Google:Oauth:client_id").ToString(),
             ["client_secret"] = Config.GetConfiguration().GetValue<string>("Google:Oauth:client_secret").ToString(),
         });

     var response = await client.SendAsync(request);

     if (response.StatusCode != HttpStatusCode.OK) return "";
     var content = await response.Content.ReadAsStringAsync();
     var result = JsonNode.Parse(content);
     return result["access_token"]?.ToString()??"";
 }

加入登入 API

這邊是使用 AppSetting.json 設定好的參數串出網址，請各位讀者自行評估。

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[HttpGet("Login")]
public ActionResult Login()
{

    string redirectUrl = Get_Oauth2Url();

    return Redirect(redirectUrl);
}

  private string Get_Oauth2Url()
  {
      string resultUrl = Config.GetConfiguration().GetValue<string>("Google:Oauth:url").ToString();
      var obj = new
      {
          scope = Config.GetConfiguration().GetValue<string>("Google:Oauth:scope").ToString(),
          access_type = Config.GetConfiguration().GetValue<string>("Google:Oauth:access_type").ToString(),
          include_granted_scopes = Config.GetConfiguration().GetValue<string>("Google:Oauth:include_granted_scopes").ToString(),
          state = Config.GetConfiguration().GetValue<string>("Google:Oauth:state").ToString(),
          redirect_uri = Config.GetConfiguration().GetValue<string>("Google:Oauth:redirect_uri").ToString(),
          response_type = Config.GetConfiguration().GetValue<string>("Google:Oauth:response_type").ToString(),
          client_id = Config.GetConfiguration().GetValue<string>("Google:Oauth:client_id").ToString(),
      };

      List<string> resultData = new();
      Type type = obj.GetType();
      var props = type.GetProperties();
      foreach (var prop in props)
      {
          string paramName = prop.Name;
          object paramValue =prop.GetValue(obj, null)??"";
          if (paramValue == null) { continue; }
          resultData.Add(paramName + "=" + paramValue.ToString());
      }
      return resultUrl + "?" + string.Join("&", resultData);
  }

登入帳號

把剛才製作的授權網址點開 https://localhost:999/Api/Google/Login 完成授權即可。


文件參考