ViewandDataAPItips:缓存AccessToken

对于云API服务，常见的方式就是按照API调用次数收费，某些API调用也就有某些限制，比如在特定时间内只允许调用指定的次数以免造成滥用。虽然Autodesk的view and Data API目前还没有应用这样的限制，但我们最好也能实现这样的机制，比如对于或者Access Token

对于云API服务，常见的方式就是按照API调用次数收费，某些API调用也就有某些限制，比如在特定时间内只允许调用指定的次数以免造成滥用。虽然Autodesk的view and Data API目前还没有应用这样的限制，但我们最好也能实现这样的机制，比如对于或者Access Token这样的操作，一个Access Token是有一定的有效期的，在这个token的有效期内，我们就没必要重复发出API调用获取新的Acces Token，只有返回仍然有效的token就可以了。下面是c#实现的简单的逻辑，用一个全局静态变量来 缓存 Access Token：

 public   class   Util 
{
     private   static   readonly   ILog  logger =  LogManager .GetLogger( typeof ( Util ));
 
     string  baseUrl =  "" ;
     RestClient  m_client;

 
     public   static   AccessToken  token;
     public   static   DateTime  issueDateTime;
     //refresh token if the token is about to expire in 5 seconds 
     public   static   int  ABOUT_EXPIRED_SECONDS = 5;
 

     public  Util( string  baseUrl)
    {
         this .baseUrl = baseUrl;
        m_client =  new   RestClient (baseUrl);
    }
 
     public   AccessToken  GetAccessToken( string  clientId,  string  clientSecret)
    {
         //no token or token is going to be expired  
         // (less than ABOUT_EXPIRED_SECONDS) 
 
         if  (token ==  null 
            || ( DateTime .Now - issueDateTime).TotalSeconds
                > (token.expires_in - ABOUT_EXPIRED_SECONDS))
        {
             RestRequest  req =  new   RestRequest ();
            req.Resource =  "authentication/v1/authenticate" ;
            req.Method =  Method .POST;
            req.AddHeader( "Content-Type" ,  "application/x-www-form-urlencoded" );
            req.AddParameter( "client_id" , clientId);
            req.AddParameter( "client_secret" , clientSecret);
            req.AddParameter( "grant_type" ,  "client_credentials" );
             //avoid CORS issue, do not use this if you just need to get access token from same domain
 
            req.AddHeader( "Access-Control-Allow-Origin" ,  "*" );
 
             IRestResponse  AccessToken > resp = m_client.Execute AccessToken >(req);
            logger.Debug(resp.Content);
 
             if  (resp.StatusCode == System.Net. HttpStatusCode .OK)
            {
                 AccessToken  ar = resp.Data;
                 if  (ar !=  null )
                {
                    token = ar;
 
                     //update the token issue time 
                    issueDateTime =  DateTime .Now;
 
 
                }
            }
             else 
            {
 
                logger.Fatal( "Authentication failed! clientId:"  + clientId);
 
            }
 
        }
         else 
        {
            ; //Do nothing, use the saved access token in static var  
        }
 
         return  token;
    }
 
 
    } 

 

当然，根据需要你可以选择其他的方式，比如把token保存在数据库中，或者memcache中。

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