Question

请有人告诉我一下如何在asp.net Web API 2.1中一起使用三个模块

Owin Middleware
HttpMessageHandler（或DelegatingHandler）
的ExceptionHandler

我要做的是开发一个web api，它将提供一个恒定格式的json数据，意味着实际数据是

{"Id":1,"UserName":"abc","Email":"abc@xyz.com"}

然后我喜欢将json作为

传递

{__d:{"Id":1,"UserName":"abc","Email":"abc@xyz.com"}, code:200, somekey: "somevalue"}

为此，我尝试使用自定义 ActionFilterAttribute ，但我觉得（仍未确认）在代码遇到异常时无法提供类似格式的数据

请建议我最好的方向。

以下是我的自定义属性的简短代码段。另外建议我自定义属性是有用的

[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class, Inherited = true, AllowMultiple = false)]
public class ResponseNormalizationAttribute : ActionFilterAttribute
{
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
            base.OnActionExecuted(actionExecutedContext);
            var response = actionExecutedContext.Response;
            object contentValue;
            if (response.TryGetContentValue(out contentValue))
            {
                var nval = new { data=contentValue, status = 200 };


                var newResponse = new HttpResponseMessage { Content = new ObjectContent(nval.GetType(), nval, new JsonMediaTypeFormatter()) };
                newResponse.Content.Headers.ContentType = new MediaTypeHeaderValue("application/json");
                actionContext.Response = newResponse;
            }
     }
}

Answer 1

如果您不使用Owin中间件，可以全局包装所有响应，这样它将使用委托处理程序返回您的常量格式json数据。

编写一个继承自DelegatingHandler的自定义处理程序：

public class ApiResponseHandler : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var response = await base.SendAsync(request, cancellationToken);

        return BuildResponse(request, response);
    }

    private static HttpResponseMessage BuildResponse(HttpRequestMessage request, HttpResponseMessage response)
    {
        object content;
        string errorMessage = null;

        if (response.TryGetContentValue(out content) && !response.IsSuccessStatusCode)
        {
            HttpError error = content as HttpError;

            if (error != null)
            {
                content = null;
                errorMessage = error.Message;
            }
        }

        var newResponse = request.CreateResponse(response.StatusCode, new ApiResponse((int)response.StatusCode, content, errorMessage));

        foreach (var header in response.Headers)
        {
            newResponse.Headers.Add(header.Key, header.Value);
        }

        return newResponse;
    }
}

//ApiResponse is your constant json response
public class ApiResponse
{

    public ApiResponse(int statusCode, object content, string errorMsg)
    {
        Code = statusCode;
        Content = content;
        Error = errorMsg;
        Id = Guid.NewGuid().ToString();
    }

    public string Error { get; set; }

    //your actual data is mapped to the Content property
    public object Content { get; set; }
    public int Code { get; private set; }
    public string Id { get; set; }
}

在WebApiConfig.cs注册处理程序：

    public static void Register(HttpConfiguration config)
    {
        // Web API routes
        config.MapHttpAttributeRoutes();
        ...

        config.MessageHandlers.Add(new ApiResponseHandler());

        config.Routes.MapHttpRoute(
            name: "DefaultApi",
            routeTemplate: "{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
        );

        ...
    }

我在SO中发布了类似的答案，但这是在.NET Core中并作为OWIN中间件实现（因为DelegatingHandler已经在.NET Core中消失了）。 How can I wrap Web API responses(in .net core) for consistency?

Owin Middleware vs ExceptionHandler vs HttpMessageHandler（DelegatingHandler）

1 个答案: