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：
<span>public</span> <span>class</span> <span>Util</span><br>{<br> <span>private</span> <span>static</span> <span>readonly</span> <span>ILog</span> logger = <span>LogManager</span>.GetLogger(<span>typeof</span>(<span>Util</span>));<br> <br> <span>string</span> baseUrl = <span>""</span>;<br> <span>RestClient</span> m_client;<br><br> <br> <span>public</span> <span>static</span> <span>AccessToken</span> token;<br> <span>public</span> <span>static</span> <span>DateTime</span> issueDateTime;<br> <span>//refresh token if the token is about to expire in 5 seconds</span><br> <span>public</span> <span>static</span> <span>int</span> ABOUT_EXPIRED_SECONDS = 5;<br> <br><br> <span>public</span> Util(<span>string</span> baseUrl)<br> {<br> <span>this</span>.baseUrl = baseUrl;<br> m_client = <span>new</span> <span>RestClient</span>(baseUrl);<br> }<br> <br> <span>public</span> <span>AccessToken</span> GetAccessToken(<span>string</span> clientId, <span>string</span> clientSecret)<br> {<br> <span>//no token or token is going to be expired </span><br> <span>// (less than ABOUT_EXPIRED_SECONDS)</span><br> <br> <span>if</span> (token == <span>null</span><br> || (<span>DateTime</span>.Now - issueDateTime).TotalSeconds<br> > (token.expires_in - ABOUT_EXPIRED_SECONDS))<br> {<br> <span>RestRequest</span> req = <span>new</span> <span>RestRequest</span>();<br> req.Resource = <span>"authentication/v1/authenticate"</span>;<br> req.Method = <span>Method</span>.POST;<br> req.AddHeader(<span>"Content-Type"</span>, <span>"application/x-www-form-urlencoded"</span>);<br> req.AddParameter(<span>"client_id"</span>, clientId);<br> req.AddParameter(<span>"client_secret"</span>, clientSecret);<br> req.AddParameter(<span>"grant_type"</span>, <span>"client_credentials"</span>);<br> <span>//avoid CORS issue, do not use this if you just need to get access token from same domain<br></span><br> req.AddHeader(<span>"Access-Control-Allow-Origin"</span>, <span>"*"</span>);<br> <br> <span>IRestResponse</span><<span>AccessToken</span>> resp = m_client.Execute<<span>AccessToken</span>>(req);<br> logger.Debug(resp.Content);<br> <br> <span>if</span> (resp.StatusCode == System.Net.<span>HttpStatusCode</span>.OK)<br> {<br> <span>AccessToken</span> ar = resp.Data;<br> <span>if</span> (ar != <span>null</span>)<br> {<br> token = ar;<br> <br> <span>//update the token issue time</span><br> issueDateTime = <span>DateTime</span>.Now;<br> <br> <br> }<br> }<br> <span>else</span><br> {<br> <br> logger.Fatal(<span>"Authentication failed! clientId:"</span> + clientId);<br> <br> }<br> <br> }<br> <span>else</span><br> {<br> ;<span>//Do nothing, use the saved access token in static var </span><br> }<br> <br> <span>return</span> token;<br> }<br> <br> <br> }
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。
