jquery getJSON回调函数没有在asp.net mvc jsonresult上触发但在twitter上运行json api

Question

从子域调用json api的问题似乎是什么？

Asp.net MVC行动

        [AllowAnonymous]
        [OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
        public JsonResult getBalances()
        {
            var balances = new[]
                               {
                                   new {Id = 1, Balance = 3},
                                   new {Id = 2, Balance = 2},
                                   new {Id = 3, Balance = 1}
                               };
            return Json(balances, JsonRequestBehavior.AllowGet);
        }

jquery代码

var url = "http://subdomain.mysite.com/getBalances/";

$.getJSON(url + '?callback=?', function (data) {
           alert(data);
        });

但是如果我使用twitter api url：

，上面的脚本就可以了

var url = "https://api.twitter.com/1/statuses/user_timeline.json?include_entities=true&include_rts=true&screen_name=twitterapi&count=2";

json的回应是： [{"Id":1,"Balance":3},{"Id":2,"Balance":2},{"Id":3,"Balance":1}]

Answer 1

我怀疑你违反了same origin policy。该代码适用于Twitter，因为Twitter支持JSONP，而您的控制器操作只返回JSON。

如果您导航到http://api.twitter.com/1/statuses/user_timeline.json?include_entities=true&include_rts=true&screen_name=twitterapi&count=2&callback=abc，您将注意到JSON响应如何与您作为查询字符串参数提供的callback包装在一起：

abc([...])

如果您希望与您的网站实现相同，则应返回JSONP。以下是您可以使用的自定义JSONP操作结果的示例：

public class JsonpResult : ActionResult
{
    private readonly object _obj;

    public JsonpResult(object obj)
    {
        _obj = obj;
    }

    public override void ExecuteResult(ControllerContext context)
    {
        var serializer = new JavaScriptSerializer();
        var callbackname = context.HttpContext.Request["callback"];
        var jsonp = string.Format("{0}({1})", callbackname, serializer.Serialize(_obj));
        var response = context.HttpContext.Response;
        response.ContentType = "application/json";
        response.Write(jsonp);
    }
}

并且您的控制器操作变为：

[AllowAnonymous]
[OutputCache(NoStore = true, Duration = 0, VaryByParam = "*")]
public JsonResult getBalances()
{
    var balances = new[]
    {
        new { Id = 1, Balance = 3 },
        new { Id = 2, Balance = 2 },
        new { Id = 3, Balance = 1 }
    };
    return new JsonpResult(balances);
}

和电话：

var url = "http://subdomain.mysite.com/getBalances/";
$.getJSON(url + '?callback=?', function (data) {
    alert(data);
});