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  • ASP.NET Web API 自定义MediaType实现jsonp跨域调用

      代码来自《ASP.NET Web API 2 框架揭秘》一书。

      直接上代码:

      

     /// <summary>
        /// 自定义jsonp MediaType
        /// </summary>
        public class JsonpMediaTypeFormatter : JsonMediaTypeFormatter
        {
            //callback参数
            public string Callback { get; private set; }
            public JsonpMediaTypeFormatter(string callback = null)
            {
                this.Callback = callback;
            }
    
            public override Task WriteToStreamAsync(Type type, object value, Stream writeStream, HttpContent content, TransportContext transportContext)
            {
                //如果callback不存在,直接调用父类方法
                if (string.IsNullOrEmpty(this.Callback))
                {
                    return base.WriteToStreamAsync(type, value, writeStream, content, transportContext);
                }
                try
                {
                    //否则调用重写的方法
                    this.WriteToStream(type, value, writeStream, content);
                    return Task.FromResult<AsyncVoid>(new AsyncVoid());
                }
                catch(Exception ex)
                {
                    TaskCompletionSource<AsyncVoid> source = new TaskCompletionSource<AsyncVoid>();
                    source.SetException(ex);
                    return source.Task;
                }
            }
    
    
            private void WriteToStream(Type type, object value, Stream writeStream, HttpContent content)
            {
                JsonSerializer serializer = JsonSerializer.Create(this.SerializerSettings);
                using (StreamWriter writer = new StreamWriter(writeStream,this.SupportedEncodings.First())) {
                    using (JsonTextWriter jsonTextWriter = new JsonTextWriter(writer) { CloseOutput = false }) {
                        //添加callback(json)
                        jsonTextWriter.WriteRaw(this.Callback + "(");
                        serializer.Serialize(jsonTextWriter, value);
                        jsonTextWriter.WriteRaw(")");
                    }
                }
            }
    
            public override MediaTypeFormatter GetPerRequestFormatterInstance(Type type, HttpRequestMessage request, MediaTypeHeaderValue mediaType)
            {
    
                if (request.Method != HttpMethod.Get) { return this; }
                string callback;
                if (request.GetQueryNameValuePairs().ToDictionary(p => p.Key, p => p.Value).TryGetValue("callback", out callback)) {
                    return new JsonpMediaTypeFormatter(callback);
                }
                return this;
            }
    
            [StructLayout(LayoutKind.Sequential, Size = 1)]
            private struct AsyncVoid { }
        }

      然后在Global.asax中将JsonpMediaTypeFormatter加入

      

     protected void Application_Start()
            { 
                //加入jsonpMediaTypeFormatter
                GlobalConfiguration.Configuration.Formatters.Insert(0, new JsonpMediaTypeFormatter());
                AreaRegistration.RegisterAllAreas();
             
                GlobalConfiguration.Configure(WebApiConfig.Register);
                FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
                RouteConfig.RegisterRoutes(RouteTable.Routes);
                BundleConfig.RegisterBundles(BundleTable.Bundles);
            }

      Demo演示:

      我在localhost:55950 用jquery 调用api(http://localhost:55599/api/search?key=%E7%83%A7%E7%81%AB&from=0&size=10)

      

      得到结果如图:

      

      成功调用。不过书上说,这种方法仅限于get方法。

      OK,笔记完成,记录下来以防以后 用到可以参考参考。

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  • 原文地址:https://www.cnblogs.com/panzi/p/5670945.html
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