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

PostRequest
        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;
        }