处理电话间隙的跨域呼叫答案

【问题标题】：Handling cross-domain calls on phone gap处理电话间隙的跨域呼叫
【发布时间】：2012-12-04 04:40:14
【问题描述】：

我正在为以下内容寻找最佳实践实现...

我有一个调用 .asmx Web 服务的 JQuery 脚本，但在域外调用时无法加载，我知道当我将 html 移至 PhoneGap 时会发生这种情况。

是使用 JSONP 的最佳/唯一解决方案吗？

我不拘泥于 .asmx 或 jquery 等。欢迎您使用过的任何有效的想法。

只需要能够从 html5 调用服务器上的方法。（而且 html5 应用程序不会离线运行）。

谢谢！

【问题讨论】：

标签： jquery cordova cross-domain jsonp asmx

【解决方案1】：

我会说 JSONP 绝对是最好的方法，如果你需要在你的服务器端代码中允许 OPTIONS 方法，你可以实现类似的代码。（注意：此示例在技术上适用于 MVC，但可以进行调整。）

public class AllowCrossSiteJsonAttribute : ActionFilterAttribute
{
    public override void OnActionExecuting(ActionExecutingContext filterContext)
    {
        HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);
        HttpContext.Current.Response.Cache.SetNoStore();

        filterContext.RequestContext.HttpContext.Response.AppendHeader("Access-Control-Allow-Origin", "*");

        string rqstMethod = HttpContext.Current.Request.Headers["Access-Control-Request-Method"];
        if (rqstMethod == "OPTIONS" || rqstMethod == "POST")
        {
            filterContext.RequestContext.HttpContext.Response.AppendHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
            filterContext.RequestContext.HttpContext.Response.AppendHeader("Access-Control-Allow-Headers", "X-Requested-With, Accept, Access-Control-Allow-Origin, Content-Type");
        }
        base.OnActionExecuting(filterContext);
    }
}

[HttpGet]
[AllowCrossSiteJsonAttribute]
public JsonpResult CommunicateCard(CommunicateCardModel ccm)
{
    return ModelState.IsValid
        ? this.ValidCommunicateCardBuilder(ccm)
        : this.InvalidFormSummary(ccm);
}

旁注：这是我正在使用的 JsonpResult。效果很棒。

namespace System.Web.Mvc
{
    #region usings
    using System;

    using WebService.Attributes;
    using WebService.Domain.Models;
    using WebService.Exceptions;
    using WebService.Models.ViewModels;
    using Extensions;
    using WebService.Utilities;
    #endregion

    public class JsonpResult : ActionResult
    {
        public Object Data { get; set; }
        public string JsonCallback { get; set; }
        public bool? Success { get; set; }


        public override void ExecuteResult(ControllerContext context)
        {

            // Create a JsonResponse that we can Send out

            // Check for the callback parameter
            this.JsonCallback = context.HttpContext.Request["callback"];

            // if the "callback" doesn't exist, we want to check for "jsoncallback"
            if (string.IsNullOrEmpty(this.JsonCallback))
                this.JsonCallback = context.HttpContext.Request["jsoncallback"];

            // If we've made it this far, we know that the object sent is an
            // object that we can serialize and Send back as valid JSON. We now
            // need to wrap it in our JsonViewModel for consistancy. NOTE: We're
            // using the AsList() extension method to ensure that we're
            // returning an Array since our application (Sencha Touch) requires
            // all data to be in array format.
            if (!Data.GetType().IsGenericType)
                Data = Data.AsList();

            // Until now we the data is either an ERROR, or null
            // if it's null, and the Data is not null, we set Success = true
            // If Success is false, it's because we set it to false when we threw an error
            // if that's the case, we keep it false for the client.
            if (Success == null) Success = true;


            var jsonViewModel = new JsonViewModel
                {
                    results = this.Data,
                    // We know that Success is either True or False so we can
                    // safely cast the nullable bool to a bool.
                    success = (bool)this.Success
                };
            WriteOut(jsonViewModel, context);
        }

        /// <summary>
        /// Write Out the JsonP Response to the Controller.
        /// </summary>
        /// <param name="jsonResponse">The unserialized object</param>
        /// <param name="context">Controller Context</param>
        private void WriteOut(JsonViewModel jsonResponse, ControllerContext context)
        {
            var response = context.HttpContext.Response;
            response.ContentType = "application/javascript";
            response.Write(JsonUtility.Serialize(jsonResponse, this.JsonCallback));
        }
    }

    /// <summary>
    /// extension methods for the controller to allow jsonp.
    /// </summary>
    public static class ContollerExtensions
    {
        public static JsonpResult Jsonp(this Controller controller, Object data)
        {
            return new JsonpResult { Data = data };
        }

        public static JsonpResult Jsonp(this Controller controller, Object data, bool success)
        {
            // We don't ever want to pass in a "true" success. We only want to 
            // know if it failed.
            if (success)
            {
                return new JsonpResult { Data = data };
            }

            return new JsonpResult { Success = false, Data = data };
        }
    }
}

【讨论】：

【解决方案2】：

是的，JSONP 是您问题的答案。 JSONP 或“带填充的 JSON”是一种 JSON 扩展，其中前缀被指定为调用本身的输入参数，并简单地克服 XMLHttpRequest 相同的域策略。