Example: Receive HTTP Post via ASP.Net Generic Handler

假設我們要提供一個小小的服務，採用HTTP協議進行通訊，用戶端 POST 一些資料到伺服器上。用戶端不一定是PC，更不一定會按照一個Web Form的格式來提交資料，它可能是一個運行在PC上的Desktop Application，也可能是一個行動裝置。

 

伺服器端接收這樣的請求極其簡單，下面寥寥數行代碼即可實現：

在Web網站中建立一個Generic Handler（*.ashx），代碼如下：

<%@ WebHandler Language="C#" Class="Echo" %>using System;using System.Web;using System.IO;public class Echo : IHttpHandler{    private System.Text.Encoding DefaultEncoding = System.Text.Encoding.UTF8;        public void ProcessRequest (HttpContext context)    {        context.Response.ContentType = "text/plain";        context.Response.ContentEncoding = DefaultEncoding;        Stream inputStream = context.Request.InputStream;        using (StreamReader reader = new StreamReader(inputStream, DefaultEncoding))        {            string requestContent = reader.ReadToEnd();            string responseContent = string.Format("Received: {0} <== END", requestContent);                        context.Response.Write(responseContent);        }    }    public bool IsReusable    {        get { return false; }    }}

然後我們寫一個簡單的用戶端來測試它。在這個用戶端裡我們實現了一個類HttpClient來進行HTTP POST操作：

// -----------------------------------------------------------------------// <copyright file="HttpClient.cs" author="Yaping Xin">// Http protocol client.// </copyright>// -----------------------------------------------------------------------namespace ConsoleClient{    using System;    using System.IO;    using System.Net;    using System.Text;    /// <summary>    /// Http protocol client.    /// </summary>    public class HttpClient    {        /// <summary>        /// Post data to specific url and get response content.        /// </summary>        /// <param name="url">the url to post</param>        /// <param name="postData">post data</param>        /// <returns>response content</returns>        public string Post(string url, string postData)        {            Uri uri = new Uri(url);            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(uri);            request.Method = "POST";            request.ContentType = "application/x-www-form-urlencoded";            Encoding encoding = Encoding.UTF8;            byte[] bytes = encoding.GetBytes(postData);            request.ContentLength = bytes.Length;            using (Stream writer = request.GetRequestStream())            {                writer.Write(bytes, 0, bytes.Length);                writer.Close();            }            return this.ReadResponse(request);;        }        /// <summary>        /// Read response content from http request result.        /// </summary>        /// <param name="request">http request object</param>        /// <returns>response content.</returns>        private string ReadResponse(HttpWebRequest request)        {            string result = string.Empty;            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())            {                using (Stream responseStream = response.GetResponseStream())                {                    using (StreamReader reader = new StreamReader(responseStream, Encoding.UTF8))                    {                        result = reader.ReadToEnd();                        reader.Close();                    }                }            }            return result;        }    }}

然後我們這樣就能得到HTTP POST的返回：

// Replace the string content with your actual address please.string defaultUrl = "http://ServerName:8081/WebPath/AnyService.ashx";HttpClient client = new HttpClient();string response = client.Post(defaultUrl, @"abc 123! 測試 @");Console.OutputEncoding = System.Text.Encoding.UTF8;Console.WriteLine(response);

假設Client與Server兩端都約定好採取某個格式對資料進行序列化與還原序列化，例如都採用Json，用戶端把對象通過Json封裝後Post給Server，Server再採用Json將對象從Json字串中解析出來，這樣進行資料傳遞是便利的。再假設我們要壓縮傳送出的資料量，那麼可以進行gzip壓縮與解壓。又假設我們要考慮安全性，那麼我們可以在對象的結構中添加security token進行認證，以及採用某種密碼編譯演算法對字串進行加密與解密。怎麼發揮就看您具體的應用了，構建一個屬於您自己的輕量的service易如反掌。