寫一個ActionFilter檢測WebApi接口請求和響應

我們一般用日志記錄每次Action的請求和響應，方便接口出錯后排查，不過如果每個Action方法內都寫操作日志太麻煩，而且客戶端傳遞了錯誤JSON或XML，沒法對應強類型參數，請求沒法進入方法內，

把日志記錄操作放在一個ActionFilter即可。

[AttributeUsageAttribute(AttributeTargets.Method, Inherited = false, AllowMultiple = false)]
public class ApiActionAttribute : ActionFilterAttribute
{
    private string _requestId;
    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        base.OnActionExecuting(actionContext);
        _requestId = DateTime.Now.Ticks.ToString();

        //獲取請求數據  
        Stream stream = actionContext.Request.Content.ReadAsStreamAsync().Result;
        string requestDataStr = "";
        if (stream != null && stream.Length > 0)
        {
            stream.Position = 0; //當你讀取完之后必須把stream的讀取位置設為開始
            using (StreamReader reader = new StreamReader(stream, System.Text.Encoding.UTF8))
            {
                requestDataStr = reader.ReadToEnd().ToString();
            }
        }

        //[POST_Request] {requestid} http://dev.localhost/messagr/api/message/send {data}
        Logger.Instance.WriteLine("[{0}_Request] {1} {2}\r\n{3}", actionContext.Request.Method.Method, _requestId, actionContext.Request.RequestUri.AbsoluteUri, requestDataStr);
    }

    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        base.OnActionExecuted(actionExecutedContext);
        string responseDataStr = actionExecutedContext.Response.Content.ReadAsStringAsync().Result;
        //[POST_Response] {requestid} {data}
        Logger.Instance.WriteLine("[{0}_Response] {1}\r\n{2}", actionExecutedContext.Response.RequestMessage.Method, _requestId, responseDataStr);
    }
}

_requestId 是用來標識請求的，根據它可以找到對應的Request與Response，便於排查。在Action上聲明：

[Route("send_email")]
[HttpPost]
[ApiAction]
[ApiException]
public async Task<SendMessageResponseDto> Send(SendEmailMessageRequestDto dto)
{
    //...
}