MVC definition Jsonpresult Implementing cross-domain requests

MVC definition Jsonpresult Implementing cross-domain requests1: Principle

in JS, XMLHttpRequest is not able to request data from different domains, but the script tag is possible, so cross-domain requests can be implemented with the script tag. Specifically, define a function, such as jsonp1234, with a function name when requesting a URL for a different domain, for example:http://otherdomain.com/index?callback=jsonp1234, The server then obtains the function name according to callback, and then passes in the JSON string as a function parameter.

2: Implementation

Http://localhost:62203/home/index The page code is as follows

@{    Layout = null;} <! DOCTYPE html>    function showmessage (result) {        alert ( result.name)    }    </script>    <script src= "Http://localhost:16308/home/index? Callback=showmessage "type=" Text/javascript "></script>

This is the main sentence.

<script src= " Http://localhost:16308/home/index?callback=showMessage " type= "Text/javascript" ></SCRIPT>

You can see that you are accessing a different site, and the parameter value of callback is ShowMessage,

Http://localhost:16308/home/index The code is as follows

 Public actionresult Index ()        {            String callback = this. Request["Callback"];            String json= "{\" name\ ": \" Server\ "}";            This. Response.Write (Callback + "(" + JSON + ")");            return new  Emptyresult ();        }

Gets the function name according to callback, and then takes the JSON string as a function parameter.

Visit Page Http://localhost:62203/home/index , the effect is as follows

Visible, the site localhost:62203 from the site localhost:16308 get the data.

But we look at the implementation of the service side, which is too ugly, but also more troublesome.

 Public actionresult Index ()        {            String callback = this. Request["Callback"];            String json= "{\" name\ ": \" Server\ "}";            This. Response.Write (Callback + "(" + JSON + ")");            return new  Emptyresult ();        }

What we want is to invoke a method that can be implemented across domains, and how to do that. See the controller has a This.json method, the type is Jsonresult, we can refer to this class. Defines a class Jsonpresult, derived from Jsonresult, in which the Executeresult method obtains the function name based on callback, and then passes in the JSON string as a function parameter.

public class Jsonpresult:jsonresult {public static readonly string jsonpcallbackname = "Callback";        public static readonly String callbackapplicationtype = "Application/json";                public override void Executeresult (ControllerContext context) {if (context = = null) {            throw new ArgumentNullException ("context"); } if ((Jsonrequestbehavior = = jsonrequestbehavior.denyget) && string.equals (context. HttpContext.Request.HttpMethod, "GET", StringComparison.OrdinalIgnoreCase)) {throw new Invalido            Perationexception (); } var response = context.            Httpcontext.response; if (! String.IsNullOrEmpty (ContentType)) response.            ContentType = ContentType; else Response.            ContentType = Callbackapplicationtype; if (contentencoding! = null) response. ContentEncoding = this. Contentencoding                if (Data! = null) {String buffer; var request = context.                HttpContext.Request;                var serializer = new JavaScriptSerializer (); if (request[jsonpcallbackname]! = null) buffer = String.Format ("{0} ({1})", Request[jsonpcallbackname], Serializer. Serialize (Data));//First gets the function name according to callback, and then passes in the JSON string as the function parameter else buffer = serializer.                Serialize (Data); Response.            Write (buffer); }        }    }

Jsonpresult class has, but want to use THIS.JSONP in this controller, so define an extension method for the Controller class,

Public Static Class controllerextension    {public        static Jsonpresult JSONP (this controller controller, object  data)        {            Jsonpresult result = New  Jsonpresult ()            {                data =  data,                jsonrequestbehavior =  Jsonrequestbehavior.allowget            };             return  result;        }    }

This is the controller can directly use the THIS.JSONP, the cross-domain service side of the code to change

 Public actionresult Index ()        {            return this. Jsonp (New {name = "Server Jsonpresult"  });        

It's a lot simpler than the one above.

Open Again Http://localhost:62203/home/index

Similarly, the site localhost:62203 from the site localhost:16308 get the data, and the same as above

MVC definition Jsonpresult Implementing cross-domain requests