接口调优——WebAPI 过滤器，IIS WebDAV

1、身份认证过滤器—AuthenticationFilter

这个是做统一身份认证授权的，这个是最先进来的，进行用户身份验证：

public class BasicAuthenticationFilterAttribute : FilterAttribute, IAuthenticationFilter

    {

        public Task AuthenticateAsync(HttpAuthenticationContext context, CancellationToken cancellationToken)

        {

            if (context.ActionContext.ActionDescriptor.GetCustomAttributes<AllowAnonymousAttribute>().Any())

            {

                return Task.FromResult();

            }

             // 具体认证业务逻辑

        }

        public Task ChallengeAsync(HttpAuthenticationChallengeContext context, CancellationToken cancellationToken)

        {

            string realm = context.Request.RequestUri.DnsSafeHost;

            context.Result = new AddBasicChallengeResult(context.Result, realm);

            return Task.FromResult();

        }

        // 错误信息生成

        public class AuthenticationFailureResult : IHttpActionResult

        {

            public AuthenticationFailureResult(HttpRequestMessage request)

            {

                Request = request;

            }

            public HttpRequestMessage Request { get; private set; }

            public Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)

            {

                return Task.FromResult(Execute());

            }

            private HttpResponseMessage Execute()

            {

                HttpResponseMessage response = new HttpResponseMessage(HttpStatusCode.Unauthorized)

                {

                    RequestMessage = Request

                };

                return response;

            }

        }

        // 认证失败返回质询信息

        private class AddBasicChallengeResult : IHttpActionResult

        {

            private IHttpActionResult innerResult;

            private string realm;

            public AddBasicChallengeResult(IHttpActionResult innerResult, string realm)

            {

                this.innerResult = innerResult;

                this.realm = realm;

            }

            public async Task<HttpResponseMessage> ExecuteAsync(CancellationToken cancellationToken)

            {

                var response = await innerResult.ExecuteAsync(cancellationToken);

                if (response.StatusCode == HttpStatusCode.Unauthorized)

                    response.Headers.WwwAuthenticate.Add(new AuthenticationHeaderValue("Basic", String.Format("realm=\"{0}\"", realm)));

                return response;

            }

        }

    }

2、Action 过滤器—ActionFilter

这个是对操作进行统一过滤的过滤器，在这个过滤器里面可以做的事情就很多，我们这里用到了：模型验证、请求信息记录、返回信息格式化；

在这里就分别说下几个具体的业务逻辑；

A、请求信息记录—RequestLogFilter

这里的记录接口请求信息，记录下每个接口请求详情，便于查看记录，具体代码：

public class RequestLogFilterAttribute : ActionFilterAttribute

    {

        private readonly string Key = "_RequestTime_";

        private readonly string Watch = "_Stopwatch_";

        private readonly string Token = ConfigurationManager.AppSettings["Token"].ToString();

        public override void OnActionExecuting(HttpActionContext actionContext)

        {

            base.OnActionExecuting(actionContext);

            Stopwatch stopWatch = new Stopwatch();

            stopWatch.Start();

            actionContext.Request.Properties[Key] = DateTime.Now;

            actionContext.Request.Properties[Watch] = stopWatch;

        }

        public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)

        {

            Stopwatch stopWatch = actionExecutedContext.Request.Properties[Watch] as Stopwatch;

            stopWatch.Stop();

            // 如果有该特性就不记录请求记录（绕过记录）

            if (actionExecutedContext.ActionContext.ActionDescriptor.GetCustomAttributes<BypassRequestLogFilterAttribute>().Any())

            {

                return;

            }

            // 具体记录接口请求信息

        }

    }

B、模型验证—ValidateModelFilter

这个是模型验证的，对接口的数据有效性进行验证

public class ValidateModelFilterAttribute : ActionFilterAttribute

    {

        public override void OnActionExecuting(HttpActionContext actionContext)

        {

            if (actionContext.ModelState.IsValid == false)

            {

                List<Dictionary<string, string>> allErrors = new List<Dictionary<string, string>>();

                var modelState = actionContext.ModelState;

                foreach (var key in modelState.Keys)

                {

                    Dictionary<string, string> errorDictionary = new Dictionary<string, string>();

                    var state = modelState[key];

                    string[] errorMessages = state.Errors.Select(t => t.ErrorMessage).ToArray();

                    errorDictionary.Add(key, string.Join(",", errorMessages));

                    allErrors.Add(errorDictionary);

                }

                ResponseData responseData = new ResponseData { MsgCode = , Message = "参数有误！", Data = allErrors };

                JsonMediaTypeFormatter jsonMediaTypeFormatter = actionContext.Request.GetConfiguration().Formatters.JsonFormatter;

                actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.BadRequest, responseData, jsonMediaTypeFormatter);

            }

        }

    }

C、返回信息格式化—ResponseFormatterFilter

之所以添加这个过滤器是在我们手机端调用接口的时候，发现返回的信息不是定义好的，

是经过了一种格式化，不能按照我们既定的格式进行解析（分析发现，是请求的时候格式化，返回的信息也按照这个格式化），

所以在过滤器里再对全部的返回信息进行格式化：

public class ResponseFormatterFilterAttribute : ActionFilterAttribute

    {

        public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)

        {

            if (actionExecutedContext.Response != null && actionExecutedContext.Response.IsSuccessStatusCode)

            {

                ObjectContent content = actionExecutedContext.Response.Content as ObjectContent;

                JsonMediaTypeFormatter jsonMediaTypeFormatter = actionExecutedContext.Request.GetConfiguration().Formatters.JsonFormatter;

                actionExecutedContext.Response = new HttpResponseMessage

                {

                    StatusCode = HttpStatusCode.OK,

                    Content = new ObjectContent(content.Value.GetType(), content.Value, jsonMediaTypeFormatter)

                };

            }

        }

    }

这几个都是继承自：ActionFilterAttribute，为了比较清晰所以分开放。

对于这种同一级别的过滤器，其执行的先后顺序是：注册在前的先进后出，注册在后的后进先出（大致如下图）

3、异常处理过滤器—ExceptionFilterAttribute

这个是统一处理有异常的过滤器，多错误过滤，返回给客户端的是处理过的，也是最后面一个出去的，过滤器里面有错误也会捕捉到。

具体代码：

public class ExceptionLogFilterAttribute : ExceptionFilterAttribute

    {

        public override void OnException(HttpActionExecutedContext actionExecutedContext)

        {

            base.OnException(actionExecutedContext);

            JsonMediaTypeFormatter jsonMediaTypeFormatter = actionExecutedContext.Request.GetConfiguration().Formatters.JsonFormatter;

            ResponseData responseData;

            if (actionExecutedContext.Exception is ExceptionEx)

            {

                responseData = new ResponseData { MsgCode = , Message = actionExecutedContext.Exception.Message };

            }

            else

            {

                Exception exceptionData = null;

                if (ConfigurationManager.AppSettings["ApplicationEnvironment"] == ApplicationEnvironmentEnum.Development.ToString())

                {

                    exceptionData = actionExecutedContext.Exception;

                }

                responseData = new ResponseData { MsgCode = , Message = "系统内部异常！请联系管理员！", Data = exceptionData };

            }

            actionExecutedContext.Response = actionExecutedContext.Request.CreateResponse(HttpStatusCode.BadRequest, responseData, jsonMediaTypeFormatter);

        }

    }

对于不同级别的过滤器，执行顺序是：

AuthenticationFilter > ActionFilterAttribute > ExceptionFilterAttribute

4、IIS WebDAV 模块

在每次发布后，出现一个问题：跨域和Put请求不了。

对于这个问题，是已经配置过的怎么还会出现这个问题。

经过反复的测试，原来是 IIS WebDAV 模块，虽然配置了，IIS 是直接修改 Webconfig 文件的，再次发布覆盖了这个文件原有的配置就没了。

对于这个问题，可以在 Webconfig 文件里面配置上，这样可以。

也可以直接去掉 WebDAV 模块，但是卸载不好卸载。可以在 IIS 站点配置文件里面删除 WebDAV 的配置，这样也可以达到效果。