webapi filter

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Runtime.Caching;
using System.Text;
using System.Web;
using System.Web.Http.Filters;


namespace SH3H.WAP.WorkSheet.Outgoing.WebApi.Filters
{
    /// <summary>
    /// 定义过滤2s内重复提交的action
    /// </summary>
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false)]
    public class FWActionSubmitFilterAttribute : ActionFilterAttribute
    {
        MemoryCacheHelper _cache = new MemoryCacheHelper();
        /// <summary>
        /// 客户端缓存（用户代理）缓存相对过期时间
        /// </summary>
        public int ClientCacheExpiration { set; get; }
        /// <summary>
        /// 服务端缓存过期时间
        /// </summary>
        public int ServerCacheExpiration { set; get; }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="clientCacheExpiration">客户端过期时间。单位为秒，默认为600秒(10分钟)</param>
        /// <param name="serverCacheExpiration">服务端过期时间。单位为秒，默认为7200秒(120分钟)</param>
        public FWActionSubmitFilterAttribute(int clientCacheExpiration = 10, int serverCacheExpiration = 30)
        {
            this.ClientCacheExpiration = clientCacheExpiration;
            this.ServerCacheExpiration = serverCacheExpiration;
        }

        /// <summary>
        /// 判定是否用缓存中的内容，还是执行action是去取内容
        /// 注：一旦给actionContext.Response赋值了，则会使用这个值来输出响应
        /// </summary>
        /// <param name="actionContext"></param>
        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
        {

            // ****************************************   穿透缓存 *********************************************
            // 若无缓存,则直接返回
            string cacheKey = getCacheKey(actionContext);
            if (_cache.Contains(cacheKey) == false)
                return;
            if (_cache.Contains(cacheKey + ":etag") == false)
                return;

            // ****************************************   使用缓存  *********************************************
            // 获取缓存中的etag
            var etag = _cache.Get<string>(cacheKey + ":etag");
            // 若etag没有被改变，则返回304，
            if (actionContext.Request.Headers.IfNoneMatch.Any(x => x.Tag == etag))  //IfNoneMatch为空时，返回的是一个集合对象
            {
                actionContext.Response = actionContext.Request.CreateResponse(HttpStatusCode.NotModified); // 响应对象还没有生成，需要先生成 // 304 not modified
                actionContext.Response.Headers.CacheControl = GetDefaultCacheControl();
                actionContext.Response.Headers.ETag = new EntityTagHeaderValue(etag);
                return;
            }
            else //从缓存中返回响应
            {
                actionContext.Response = actionContext.Request.CreateResponse(); // 响应对象还没有生成，需要先生成
                // 设置协商缓存：etag
                actionContext.Response.Headers.ETag = new EntityTagHeaderValue(etag); //用缓存中的值（为最新的）更新它
                // 设置user agent的本地缓存
                actionContext.Response.Headers.CacheControl = GetDefaultCacheControl();

                // 从缓存中取中响应内容
                var content = _cache.Get<byte[]>(cacheKey);
                actionContext.Response.Content = new ByteArrayContent(content);
                return;
            }
        }






        /// <summary>
        ///  将输出保存在缓存中。
        /// </summary>
        /// <param name="actionExecutedContext"></param>
        /// <param name="cancellationToken"></param>
        /// <returns></returns>
        public override async System.Threading.Tasks.Task OnActionExecutedAsync(HttpActionExecutedContext actionExecutedContext, System.Threading.CancellationToken cancellationToken)
        {
            // 响应对象已经生成，可以直接调用   actionExecutedContext.Response

            // 设置协商缓存：etag
            EntityTagHeaderValue etag = new EntityTagHeaderValue(""" + Guid.NewGuid().ToString() + """);  // 根据http协议， ETag的值必须用引号包含起来
            actionExecutedContext.Response.Headers.ETag = etag;
            // 设置user agent的本地缓存
            actionExecutedContext.Response.Headers.CacheControl = GetDefaultCacheControl();

            // actionExecutedContext.Response.Headers.Remove("Content-Length"); // 改变了值，它会发生变化。删除它的话，后续的程序会自动地再计算

            // 保存到缓存
            string cacheKey = getCacheKey(actionExecutedContext.ActionContext);
            var contentBytes = await actionExecutedContext.Response.Content.ReadAsByteArrayAsync();

            _cache.Add(cacheKey + ":etag", etag.Tag, DateTimeOffset.Now.AddSeconds(this.ServerCacheExpiration));
            _cache.Add(cacheKey, contentBytes, DateTimeOffset.Now.AddSeconds(this.ServerCacheExpiration));

        }





        /// <summary>
        /// 默认的用户代理本地缓存配置，10分钟的相对过期时间
        /// 对应响应header中的 Cache-Control
        /// 这里设置里面的子项max-age。如：Cache-Control: max-age=3600
        /// </summary>
        /// <returns></returns>
        CacheControlHeaderValue GetDefaultCacheControl()
        {
            CacheControlHeaderValue control = new CacheControlHeaderValue();
            control.MaxAge = TimeSpan.FromSeconds(this.ClientCacheExpiration);  // 它对应响应头中的 cacheControl :max-age=10项

            return control;
        }




        /// <summary>
        /// 
        /// </summary>
        /// <param name="actionContext"></param>
        /// <returns></returns>
        string getCacheKey(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            string cacheKey = null;
　　　　　　　　　//获取POST中data
            var context = (HttpContextBase)actionContext.Request.Properties["MS_HttpContext"];
            context.Request.InputStream.Seek(0, SeekOrigin.Begin);
            using (var sr = new StreamReader(context.Request.InputStream, Encoding.UTF8, true, 1024, true))
            {
                string body = sr.ReadToEnd();
                // Logging here...

            }

　　　　　　
            cacheKey = actionContext.Request.RequestUri.PathAndQuery; // 路径和查询部分,如： /api/values/1?ee=33&oo=5

            // 对路径中的参数进行重排，升序排列

            string controllerName = actionContext.ControllerContext.ControllerDescriptor.ControllerName;
            string actionName = actionContext.ActionDescriptor.ActionName;

            if (actionContext.ActionArguments.ContainsKey("id") == false)
            {
                cacheKey = controllerName + "/" + actionName;
            }
            else
            {
                string id = actionContext.ActionArguments["id"].ToString();
                cacheKey = controllerName + "/" + actionName + "/" + id;
            }

            return cacheKey;
        }

    }



    /// <summary>
    /// 缓存辅助类
    /// </summary>
    public class MemoryCacheHelper
    {
        private static readonly MemoryCache _cache = MemoryCache.Default;

        /// <summary>
        /// 
        /// </summary>
        /// <param name="key"></param>
        public void RemoveStartsWith(string key)
        {
            lock (_cache)
            {
                _cache.Remove(key);
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="key"></param>
        /// <returns></returns>
        public T Get<T>(string key) where T : class
        {
            var o = _cache.Get(key) as T;
            return o;
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        [Obsolete("Use Get<T> instead")]
        public object Get(string key)
        {
            return _cache.Get(key);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="key"></param>
        public void Remove(string key)
        {
            lock (_cache)
            {
                _cache.Remove(key);
            }
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="key"></param>
        /// <returns></returns>
        public bool Contains(string key)
        {
            return _cache.Contains(key);
        }
        /// <summary>
        /// 
        /// </summary>
        /// <param name="key"></param>
        /// <param name="o"></param>
        /// <param name="expiration"></param>
        /// <param name="dependsOnKey"></param>
        public void Add(string key, object o, DateTimeOffset expiration, string dependsOnKey = null)
        {
            var cachePolicy = new CacheItemPolicy
            {
                AbsoluteExpiration = expiration
            };

            if (!string.IsNullOrWhiteSpace(dependsOnKey))
            {
                cachePolicy.ChangeMonitors.Add(
                    _cache.CreateCacheEntryChangeMonitor(new[] { dependsOnKey })
                );
            }
            lock (_cache)
            {
                _cache.Add(key, o, cachePolicy);
            }
        }
        /// <summary>
        /// 
        /// </summary>
        public IEnumerable<string> AllKeys
        {
            get
            {
                return _cache.Select(x => x.Key);
            }
        }
    }
}