基于.Net Framework 4.0 Web API开发（3）：ASP.NET Web APIs 异常的统一处理Attribute 和统一写Log 的Attribute的实现

概述： 

　　ASP.NET Web API 的好用使用过的都知道，没有复杂的配置文件，一个简单的ApiController加上需要的Action就能工作。但是项目，总有异常发生，本节就来谈谈API的异常的统一处理和写统一写log逻辑的解决方案。

问题：

　　 在ASP.NET Web API编写时，如果每个API都写异常处理逻辑，不但加大了开发工作量，且每个开发人员处理异常返回的数据结构也不尽相同，在异常发生情况下，客户端处理异常的逻辑就不再通用，也同时加大了对接接口人员的工作量，好的API错误码和错误信息都是固定格式，并后台应该有相应的异常记录。

异常的统一处理的实现：

1. 首先定义异常处理Attribute，继承System.Web.Http.Filters.ExceptionAttribute, 重写OnException， 代码如下

   public class ErrorHandleAttribute : System.Web.Http.Filters.ExceptionFilterAttribute
     {
         private string _msg = string.Empty;

         public ErrorHandleAttribute() { }

         public ErrorHandleAttribute(string msg)
         {
             this._msg = msg;
         }
         public override void OnException(System.Web.Http.Filters.HttpActionExecutedContext actionExecutedContext)
         {
             base.OnException(actionExecutedContext);
             // 取得发生异常时的错误讯息
             //var errorMessage = actionExecutedContext.Exception.Message;
             // 标记log
             var logAction = actionExecutedContext.ActionContext.ActionDescriptor.GetCustomAttributes<NoErrorHandlerAttribute>();
             if (logAction.Any())
             {
                 actionExecutedContext.Response = actionExecutedContext.Request.CreateResponse(System.Net.HttpStatusCode.InternalServerError, new ResultData(ResultType.SystemException, actionExecutedContext.Exception.Message));
                 return;
             }

             var request = HttpContext.Current.Request;
             var logDetail = new LogDetail
             {
                 //获取action名称
                 ActionName = actionExecutedContext.ActionContext.ActionDescriptor.ActionName,
                 //获取Controller 名称
                 ControllerName = actionExecutedContext.ActionContext.ActionDescriptor.ControllerDescriptor.ControllerName,
                 Navigator = request.UserAgent,
                 //获取访问的ip
                 IP = request.UserHostAddress,
                 UserHostName = request.UserHostName,
                 UrlReferrer = request.UrlReferrer != null ? request.UrlReferrer.AbsoluteUri : "",
                 Browser = request.Browser.Browser + " - " + request.Browser.Version + " - " + request.Browser.Type,
                 //获取request提交的参数
                 Paramaters = GetRequestValues(actionExecutedContext),
                 //获取response响应的结果
                 //ExecuteResult = GetResponseValues(actionExecutedContext),  //这句会报错，异常没有处理结果
                 AttrTitle = this._msg,
                 ErrorMsg = string.Format("错误信息：{0}， 异常跟踪：{1}", actionExecutedContext.Exception.Message, actionExecutedContext.Exception.StackTrace),
                 RequestUri = request.Url.AbsoluteUri
             };

             // 写log
             var logRep = ContainerManager.Resolve<ISysLogRepository>();
             var log = new Log()
             {
                 Action = actionExecutedContext.ActionContext.ActionDescriptor.ControllerDescriptor.ControllerName + "/" + actionExecutedContext.ActionContext.ActionDescriptor.ActionName,
                 CreateDate = DateTime.Now,
                 CreatorLoginName = RISContext.Current.CurrentUserInfo.UserName,
                 IpAddress = request.UserHostAddress,
                 Detail = Utility.JsonSerialize<LogDetail>(logDetail)
             };

             logRep.Add(log);
             actionExecutedContext.Response = actionExecutedContext.Request.CreateResponse(System.Net.HttpStatusCode.InternalServerError, new ResultData(ResultType.SystemException, actionExecutedContext.Exception.Message));
         }

         /// <summary>
         /// 读取request 的提交内容
         /// </summary>
         /// <param name="actionExecutedContext"></param>
         /// <returns></returns>
         public string GetRequestValues(HttpActionExecutedContext actionExecutedContext)
         {

             Stream stream = actionExecutedContext.Request.Content.ReadAsStreamAsync().Result;
             Encoding encoding = Encoding.UTF8;
             /*
                 这个StreamReader不能关闭，也不能dispose， 关了就傻逼了
                 因为你关掉后，后面的管道  或拦截器就没办法读取了
             */
             var reader = new StreamReader(stream, encoding);
             string result = reader.ReadToEnd();
             /*
             这里也要注意：   stream.Position = 0;
             当你读取完之后必须把stream的位置设为开始
             因为request和response读取完以后Position到最后一个位置，交给下一个方法处理的时候就会读不到内容了。
             */
             stream.Position = ;
             return result;
         }
     }

2. 接下来定义不需要异常处理的Attribute，代码如下：

     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true)]
     public class NoErrorHandlerAttribute : Attribute
     {
     }

3. 在HttpConfiguration中注册使用 ErrorHandleAttribute， 注册代码如下：

config.Filters.Add(new ErrorHandleAttribute("错误处理"));

一般在项目的WebApiConfig.cs中注册此属性：

  /// <summary>
     /// WebApiConfig
     /// </summary>
     public static class WebApiConfig
     {
         /// <summary>
         /// WebApiConfig Register
         /// </summary>
         /// <param name="config"></param>
         public static void Register(HttpConfiguration config)
         {
             //config.Filters.Add(new TokenAuthorizeAttribute());
             config.MessageHandlers.Add(new CrosHandler());
             config.Filters.Add(new ApiAuthorizeAttribute());
             config.Filters.Add(new ErrorHandleAttribute("错误处理"));
             // Web API 路由
             config.Routes.MapHttpRoute(
                 name: "DefaultApi",
                 routeTemplate: "mobileapi/{controller}/{action}/{id}",
                 defaults: new { controller = "Test", action = "GetTestValue", id = RouteParameter.Optional }
             );
         }
     }

这样就可以了，在每个Action中就不要写try catch了，否则不执行ErrorHandle中异常处理逻辑
4. 如果特殊的Controller或者Action不需要纪录和处理异常，可以在Controller或者Action上添加[NoErrorHandler],这样就不会执行ErrorHandle中异常处理逻辑

以上部分是异常的统一处理逻辑, 接下来实现统一写Log的 Attribute功能

统一写Log的 Attribute功能实现：

1. 首先定义写Log的Attribute，继承System.Web.Http.Filters.ActionFilterAttribute，重写OnActionExecuting和OnActionExecuted，代码如下：

  public class LogAttribute : ActionFilterAttribute
     {
         private string _msg = string.Empty;
         private string _token = string.Empty;
         private string _remark = string.Empty;
         public LogAttribute() { }

         public LogAttribute(string msg)
         {
             this._msg = msg;
         }

         //http://www.cnblogs.com/shan333chao/p/5002054.html
         private static readonly string key = "enterTime";
         private const string UserToken = "token";
         public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
         {
             if (actionContext.Request.Method != HttpMethod.Options)
             {
                 // 标记log
                 var logAction = actionContext.ActionDescriptor.GetCustomAttributes<NoLogAttribute>();
                 if (!logAction.Any())
                 {
                     actionContext.Request.Properties[key] = DateTime.Now.ToBinary();
                     this._token = GetToken(actionContext, out this._remark);
                 }
             }
             base.OnActionExecuting(actionContext);
         }

         public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
         {
             if (actionExecutedContext.Request.Method != HttpMethod.Options)
             {
                 object beginTime = null;
                 if (actionExecutedContext.Request.Properties.TryGetValue(key, out beginTime))
                 {
                     DateTime time = DateTime.FromBinary(Convert.ToInt64(beginTime));
                     var request = HttpContext.Current.Request;
                     var logDetail = new LogDetail
                     {
                         //获取action名称
                         ActionName = actionExecutedContext.ActionContext.ActionDescriptor.ActionName,
                         //获取Controller 名称
                         ControllerName = actionExecutedContext.ActionContext.ActionDescriptor.ControllerDescriptor.ControllerName,
                         //获取action开始执行的时间
                         EnterTime = time,
                         //获取执行action的耗时
                         CostTime = (DateTime.Now - time).TotalMilliseconds,
                         Navigator = request.UserAgent,
                         Token = this._token,
                         //获取用户ID
                         UId = UserTokenManager.GetUId(this._token),
                         //获取访问的ip
                         IP = request.UserHostAddress,
                         UserHostName = request.UserHostName,
                         UrlReferrer = request.UrlReferrer != null ? request.UrlReferrer.AbsoluteUri : "",
                         Browser = request.Browser.Browser + " - " + request.Browser.Version + " - " + request.Browser.Type,
                         //获取request提交的参数
                         Paramaters = GetRequestValues(actionExecutedContext),
                         //获取response响应的结果
                         ExecuteResult = GetResponseValues(actionExecutedContext),
                         AttrTitle = this._msg,
                         Remark = this._remark,
                         RequestUri = request.Url.AbsoluteUri
                     };

                     // 登录log
                     var logRep = ContainerManager.Resolve<ISysLogRepository>();
                     var log = new Log()
                     {
                         Action = actionExecutedContext.ActionContext.ActionDescriptor.ControllerDescriptor.ControllerName + "/" + actionExecutedContext.ActionContext.ActionDescriptor.ActionName,
                         CreateDate = DateTime.Now,
                         CreatorLoginName = RISContext.Current.CurrentUserInfo.UserName,
                         IpAddress = request.UserHostAddress,
                         Detail = Utility.JsonSerialize<LogDetail>(logDetail)
                     };

                     logRep.Add(log);
                 }
             }

             base.OnActionExecuted(actionExecutedContext);
         }

         private string GetToken(System.Web.Http.Controllers.HttpActionContext actionContext, out string msg)
         {
             Dictionary<string, object> actionArguments = actionContext.ActionArguments;
             HttpMethod type = actionContext.Request.Method;
             msg = "";
             var token = "";
             if (type == HttpMethod.Post)
             {
                 if (actionArguments.ContainsKey(UserToken))
                 {
                     if (actionArguments[UserToken] != null)
                         token = actionArguments[UserToken].ToString();
                 }
                 else
                 {
                     foreach (var value in actionArguments.Values)
                     {
                         if (value != null && value.GetType().GetProperty(UserToken) != null)
                             token = value.GetType().GetProperty(UserToken).GetValue(value, null).ToString();
                     }
                 }

                 if (string.IsNullOrEmpty(token))
                     msg = "匿名用户";
             }
             else if (type == HttpMethod.Get)
             {
                 if (!actionArguments.ContainsKey(UserToken))
                     msg = "匿名用户";
                 // throw new HttpException(401, "还未登录");

                 if (actionArguments[UserToken] != null)
                     token = actionArguments[UserToken].ToString();
                 else
                     msg = "匿名用户";
             }
             else if (type == HttpMethod.Options)
             {

             }
             else
             {
                 throw new HttpException(, "暂未开放除POST，GET之外的访问方式!");
             }
             return token;
         }
         /// <summary>
         /// 读取request 的提交内容
         /// </summary>
         /// <param name="actionExecutedContext"></param>
         /// <returns></returns>
         public string GetRequestValues(HttpActionExecutedContext actionExecutedContext)
         {

             Stream stream = actionExecutedContext.Request.Content.ReadAsStreamAsync().Result;
             Encoding encoding = Encoding.UTF8;
             /*
                 这个StreamReader不能关闭，也不能dispose， 关了就傻逼了
                 因为你关掉后，后面的管道  或拦截器就没办法读取了
             */
             var reader = new StreamReader(stream, encoding);
             string result = reader.ReadToEnd();
             /*
             这里也要注意：   stream.Position = 0;
             当你读取完之后必须把stream的位置设为开始
             因为request和response读取完以后Position到最后一个位置，交给下一个方法处理的时候就会读不到内容了。
             */
             stream.Position = ;
             return result;
         }

         /// <summary>
         /// 读取action返回的result
         /// </summary>
         /// <param name="actionExecutedContext"></param>
         /// <returns></returns>
         public string GetResponseValues(HttpActionExecutedContext actionExecutedContext)
         {
             Stream stream = actionExecutedContext.Response.Content.ReadAsStreamAsync().Result;
             Encoding encoding = Encoding.UTF8;
             /*
             这个StreamReader不能关闭，也不能dispose， 关了就傻逼了
             因为你关掉后，后面的管道  或拦截器就没办法读取了
             */
             var reader = new StreamReader(stream, encoding);
             string result = reader.ReadToEnd();
             /*
             这里也要注意：   stream.Position = 0;
             当你读取完之后必须把stream的位置设为开始
             因为request和response读取完以后Position到最后一个位置，交给下一个方法处理的时候就会读不到内容了。
             */
             stream.Position = ;
             return result;
         }
     }

2. 接下来定义不需要记录log的Attribute，代码如下：

     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true)]
     public class NoErrorHandlerAttribute : Attribute
     {
     }

3. 注意不要在HttpConfiguration中注册使用 LogAttribute，除非你想所有的请求都写log，在不需要写log的Action上添加[NoLog]，否则只需要在需要记录log的Action添加[Log]就可以完成写log的功能。

此篇到此结束，相对比较简单，欢迎大家讨论！