c# - 如何自定义 415 状态码的错误信息？

Question

我们已将媒体类型限制为“application/json”。因此，如果请求 header 包含“Content-Type:text/plain”，它会响应以下错误消息和状态代码 415。这种行为是预期的，但我想发送状态代码为 415 的空响应。我们如何在 .网络 API？

{
   "message": "The request entity's media type 'text/plain' is not supported for this resource.",
   "exceptionMessage": "No MediaTypeFormatter is available to read an object of type 'MyModel' from content with media type 'text/plain'.",
   "exceptionType": "System.Net.Http.UnsupportedMediaTypeException",
   "stackTrace": "   at System.Net.Http.HttpContentExtensions.ReadAsAsync[T](HttpContent content, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)\r\n   at System.Web.Http.ModelBinding.FormatterParameterBinding.ReadContentAsync(HttpRequestMessage request, Type type, IEnumerable`1 formatters, IFormatterLogger formatterLogger, CancellationToken cancellationToken)"
}

Answer 1

您可以创建消息处理程序，它将在管道早期检查请求的内容类型，如果不支持请求内容类型，则返回 415 状态代码和空主体:

public class UnsupportedContentTypeHandler : DelegatingHandler
{
    private readonly MediaTypeHeaderValue[] supportedContentTypes =
    {
        new MediaTypeHeaderValue("application/json")
    };

    protected async override Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        var contentType = request.Content.Headers.ContentType;
        if (contentType == null || !supportedContentTypes.Contains(contentType))
            return request.CreateResponse(HttpStatusCode.UnsupportedMediaType);

        return await base.SendAsync(request, cancellationToken);
    }
}

将此消息处理程序添加到 http 配置的消息处理程序(在 WebApiConfig):

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

对于所有未提供内容类型或内容类型不受支持的请求，您将得到空响应。

请注意，您可以从全局配置中获取支持的媒体类型(以避免重复此数据):

public UnsupportedContentTypeHandler()
{
    supportedContentTypes = GlobalConfiguration.Configuration.Formatters
                                .SelectMany(f => f.SupportedMediaTypes).ToArray();
}