Asp.net WebAPi gzip压缩和json格式化

现在webapi越来越流行了，很多时候它都用来做接口返回json格式的数据，webapi原本是根据客户端的类型动态序列化为json和xml的，但实际很多时候我们都是序列化为json的，所以webapi的序列化比我们用ServiceStack.Text序列化要多花费一些时间，还有如果返回的数据量比较大那么我们应该启动gzip和deflate压缩。而这些实现都不得影响现有的code， 我个人喜欢同时也是习惯用特性来完成压缩和json格式化。

1.压缩的code：

namespace MvcApp
{
    using System;
    using System.Collections.Generic;
    using System.IO;
    using System.Linq;
    using System.Web;
    using System.Web.Http.Filters;
    using System.IO.Compression;
    using System.Net.Http;
    public class CompressAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
        {
            var content = actionExecutedContext.Response.Content;
            var acceptEncoding = actionExecutedContext.Request.Headers.AcceptEncoding.Where(x => x.Value == "gzip" || x.Value == "deflate").ToList();
            if (acceptEncoding != null && acceptEncoding.Count > 0 && content != null && actionExecutedContext.Request.Method != HttpMethod.Options)
            {
                var bytes = content.ReadAsByteArrayAsync().Result;
                if (acceptEncoding.FirstOrDefault().Value == "gzip")
                {
                    actionExecutedContext.Response.Content = new ByteArrayContent(CompressionHelper.GzipCompress(bytes));
                    actionExecutedContext.Response.Content.Headers.Add("Content-Encoding", "gzip");
                }
                else if (acceptEncoding.FirstOrDefault().Value == "deflate")
                {
                    actionExecutedContext.Response.Content = new ByteArrayContent(CompressionHelper.DeflateCompress(bytes));
                    actionExecutedContext.Response.Content.Headers.Add("Content-encoding", "deflate");
                }
            }
            base.OnActionExecuted(actionExecutedContext);
        }

    }
    class CompressionHelper
    {

        public static byte[] DeflateCompress(byte[] data)
        {
            if (data == null || data.Length < 1)
                return data;
            try
            {
                using (MemoryStream stream = new MemoryStream())
                {
                    using (DeflateStream gZipStream = new DeflateStream(stream, CompressionMode.Compress))
                    {
                        gZipStream.Write(data, 0, data.Length);
                        gZipStream.Close();
                    }
                    return stream.ToArray();
                }
            }
            catch (Exception)
            {
                return data;
            }
        }

        public static byte[] GzipCompress(byte[] data)
        {
            if (data == null || data.Length < 1)
                return data;
            try
            {
                using (MemoryStream stream = new MemoryStream())
                {
                    using (GZipStream gZipStream = new GZipStream(stream, CompressionMode.Compress))
                    {
                        gZipStream.Write(data, 0, data.Length);
                        gZipStream.Close();
                    }
                    return stream.ToArray();
                }
            }
            catch (Exception)
            {
                return data;
            }

        }
    }
}

首先判断客户端是否启动gzip，deflate压缩，如果启用并且请求类型不是Options同时又返回数据，那么我们就压缩返回数据。至于用gzip还是deflate那就看客户端接受的一个压缩是gzip，deflate？

2.json

如下：

public IEnumerable<Users> Get()
{
return _userList;
}

很多时候我们会把这个api的返回类型改为HttpResponseMessage同时序列化为json格式的数据，写成一个通用的方法大家来调用。我推荐的实现方式采用Attribute来做。

相关code：

namespace MvcApp
{
    using ServiceStack.Text;
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Net;
    using System.Net.Http;
    using System.Reflection;
    using System.Text;
    using System.Web;
    using System.Web.Http.Controllers;
    using System.Web.Http.Filters;
    public class JsonResultConverterAttribute : ActionFilterAttribute
    {
        public override void OnActionExecuting(System.Web.Http.Controllers.HttpActionContext actionContext)
        {
            //actionContext.ActionDescriptor.ResultConverter ;
            var actionDescriptor = actionContext.ActionDescriptor;
            var field = typeof(HttpActionDescriptor).GetField("_converter", BindingFlags.NonPublic | BindingFlags.Instance);
          if (field != null)
          {
              field.SetValue(actionDescriptor, new JsonResultConverter());
              //actionDescriptor.ReturnType = typeof(HttpResponseMessage);
          }
          var test = actionDescriptor.ResultConverter;
            base.OnActionExecuting(actionContext);
        }
    }
    public class JsonResultConverter : IActionResultConverter
    {
        public HttpResponseMessage Convert(HttpControllerContext controllerContext, object actionResult)
        {
            if (controllerContext == null)
            {
                throw  new ArgumentNullException("controllerContext");
            }

            HttpResponseMessage resultAsResponse = actionResult as HttpResponseMessage;
            if (resultAsResponse != null)
            {
               // resultAsResponse.EnsureResponseHasRequest(controllerContext.Request);
                return resultAsResponse;
            }

            string jsonResult = TypeSerializer.SerializeToString(actionResult);
           var content = new StringContent(jsonResult, Encoding.UTF8, "application/json");

           return controllerContext.Request.CreateResponse(HttpStatusCode.OK, jsonResult);
        }
    }
}

注意HttpActionDescriptor的私有字段_converter在ResultConverter属性中暴露出来，遗憾的是是个只读属性，所以我们需要用反射来设置它的value（实现IActionResultConverter接口）。

运行结果我也就不贴图了，代码下载地址：http://download.csdn.net/detail/dz45693/9486586