JS通过服务代理调用跨域服务

这里讲的是服务代理，应用情景如下：
 A站点有一个JS脚本需要调用B站点的服务接口，但是A站点和B站点不是同一个域名下，这样就关系到跨域访问的了问题了，一种解决方法是通过一个代理去接管所有对B站点服务的调用。
服务器端：AcrossServer.ashx

public class AcrossServer : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";

        string clientKey = context.Request["ClientKey"];
        string clientIP = context.Request["ClientIP"];

        context.Response.Write(string.Format("AcrossServer：ClientKey={0}, ClientIP={1}", clientKey, clientIP));
    }

}

代理服务：

public class AcrossClient : IHttpHandler {
    
    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "text/plain";

        //构造Post数据
        string clientKey = "af8b908b-7735-4db6-9d8f-eef05b2eef69";
        string clientIP = context.Request.UserHostAddress;
        StringBuilder sb = new StringBuilder();
        sb.AppendFormat("ClientKey={0}&ClientIP={1}", clientKey, clientIP);
        foreach (string key in context.Request.Form.AllKeys)
        {
            sb.AppendFormat("&{0}={1}", key, context.Request.Form[key]);
        }
        string postData = sb.ToString();
        byte[] data = Encoding.UTF8.GetBytes(postData);

        //HttpWebRequest
        string url = string.Format("http://my2.csdn.net/Samples/CJB3/AcrossServer.ashx");
        HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
        request.Method = "POST";
        request.ContentType = "application/x-www-form-urlencoded";
        request.ContentLength = data.Length;
        request.Timeout = 10000;//10s

        string content = string.Empty;
        try
        {
            //把postdata写入HttpWebRequest
            using (Stream requestStream = request.GetRequestStream())
            {
                requestStream.Write(data, 0, data.Length);
                requestStream.Close();
            }
            //获取HttpWebResponse
            using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
            {
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    using (Stream stream = response.GetResponseStream())
                    {
                        using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                        {
                            content = reader.ReadToEnd();
                            reader.Close();
                        }
                        stream.Close();
                    }
                }
                response.Close();
            }
        }
        catch (System.Net.WebException)
        {
            //TODO:考虑在此添加超时异常的日志
        }
        finally
        {
            if (request != null)
            {
                request.Abort();
                request = null;
            }
        }
        
        context.Response.Write(string.Format("AcrossClient=>{0}", content));
    }

}

我们通过在代理端重新封装所有的Post数据并且添加新的服务验证等数据一起Post到真正的服务接口，最后把调用的返回也返回给代理调用方。

当然，我们可以对Post操作进一步封装到一个方法

        public static string PostRequest(string url, byte[] data, int timeout)
        {
            //HttpWebRequest
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(url);
            request.Method = "POST";
            request.ContentType = "application/x-www-form-urlencoded";
            request.ContentLength = data.Length;
            request.Timeout = timeout;

            string content = string.Empty;
            try
            {
                //把postdata写入HttpWebRequest
                using (Stream requestStream = request.GetRequestStream())
                {
                    requestStream.Write(data, 0, data.Length);
                    requestStream.Close();
                }
                //获取HttpWebResponse
                using (HttpWebResponse response = (HttpWebResponse)request.GetResponse())
                {
                    if (response.StatusCode == HttpStatusCode.OK)
                    {
                        using (Stream stream = response.GetResponseStream())
                        {
                            using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
                            {
                                content = reader.ReadToEnd();
                                reader.Close();
                            }
                            stream.Close();
                        }
                    }
                    response.Close();
                }
            }
            finally
            {
                if (request != null)
                {
                    request.Abort();
                    request = null;
                }
            }
            return content;
        }