C# WebAPI 中过滤器Filter应用之IP访问控制

        我们在做后台接口开发的时候，为了保障接口访问安全，IP访问控制是必不可少的，这里运用filter的特性来完成接口访问控制。

        Filter在Web API中经常会用到，主要用于记录日志，安全验证，全局错误处理等，通过Filter能统一地对一些通用逻辑进行处理。在默认的WebApi中，框架提供了2种Filter，分别继承actionfilterattribute，exceptionfilterattribute。actionfilter主要实现执行请求方法体之前和之后的事件处理，exceptionfilter主要实现触发异常方法。

        这里使用actionfilter来完成IP访问控制：

1、在接口类/方法添加过滤器

    [AccessFilter]
    public class PasswordController : ApiController
    {
        public ResponseModel Get(string openId)
        {
            if (string.IsNullOrEmpty(openId))
            {
                LogHelper.Info(Resource.OpenIdInvalid);
                response.Message = Resource.OpenIdInvalid;
                return response;
            }
        }
     }

 2、新建ActionFilter类

 public class AccessFilter : ActionFilterAttribute
    {
        /// 

        /// 过滤器主方法
        /// 
        /// 
        public override void OnActionExecuting(HttpActionContext actionContext)
        {
            try
            {
                var ip = GetClientIp(actionContext.Request);
                var constrollers = ClientConfigHelper.ClientModels;
                var validClient = constrollers.FirstOrDefault(item => item.Ip.Equals(ip));
                if (validClient == null || !validClient.Enabled)
                {
                    HandleRequest(actionContext, EnumResponseCode.Unauthorized);
                }
            }
            catch (Exception exception)
            {
                LogHelper.Error(Resource.ExecutingActionFilterError, exception);
            }
        }

        /// 

        /// 获取请求的IP地址
        /// 
        /// 
        /// 
        private string GetClientIp(HttpRequestMessage request)
        {
            if (request.Properties.ContainsKey("MS_HttpContext"))
            {
                return ((HttpContextWrapper)request.Properties["MS_HttpContext"]).Request.UserHostAddress;
            }
            else if (request.Properties.ContainsKey(RemoteEndpointMessageProperty.Name))
            {
                RemoteEndpointMessageProperty prop;
                prop = (RemoteEndpointMessageProperty)request.Properties[RemoteEndpointMessageProperty.Name];
                return prop.Address;
            }
            else
            {
                return null;
            }
        }

        /// 

        /// 请求处理
        /// 
        /// 
        /// 
        private void HandleRequest(HttpActionContext actionContext, EnumResponseCode code)
        {
            var message = EnumHelper.GetEnumDescription(code);
            var result = new ResponseModel { Code = (int)code, Message = message };
            actionContext.Response = actionContext.Request.CreateResponse(
                HttpStatusCode.OK,
                result,
                actionContext.ControllerContext.Configuration.Formatters.JsonFormatter
            );
        }
    }

3、获取配置文件授权IP地址信息

    public class ClientConfigHelper
    {
        private ClientConfigHelper() { }

        static ClientConfigHelper()
        {
            var path = string.Format("{0}App_Data\\controllers.config", AppDomain.CurrentDomain.BaseDirectory);
            ClientModels = JsonHelper.DeserializeObjectFromFile>(path);
        }
        public static List ClientModels { get; private set; }
    }