.Net Core MVC - 无法获得 406 - 不可接受，始终使用 Json 返回 200 OK

Question

我希望我的应用程序尊重浏览器接受标头并返回 406，如果它与响应格式不匹配。

我在 Mvc 配置中设置了这个选项：

    /// <summary>
    /// This method gets called by the runtime. Use this method to add services to the container.
    /// </summary>
    /// <param name="services">The collection of the services.</param>
    /// <returns>The provider of the service.</returns>
    public IServiceProvider ConfigureServices(IServiceCollection services)
    {
        // add mvc services
        services.AddMvc(options =>
                {
                    options.RespectBrowserAcceptHeader = true;
                    options.ReturnHttpNotAcceptable = true;

                    options.CacheProfiles.Add(
                        "CodebookCacheProfile",
                        new CacheProfile()
                        {
                            Duration = (int)TimeSpan.FromDays(1).TotalSeconds
                        });
                })
                .AddControllersAsServices()
                .AddJsonOptions(options =>
                {
                    options.SerializerSettings.Converters.Add(new StringEmptyToNullConverter());
                    options.SerializerSettings.Converters.Add(new StringEnumConverter(true));
                });

        // add response compression services
        services.AddResponseCompression(options =>
        {
            options.EnableForHttps = true;
            options.Providers.Add<GzipCompressionProvider>();
        });

        // add application services
        services.AddSwaggerDoc()
                .AddConfiguration(configuration)
                .AddModel()
                .AddDataAccess(configuration)
                .AddAuthentication(configuration)
                .AddDomainServices()
                .AddSchedulerContainer(() => serviceProvider);

        // initialize container
        serviceProvider = services.CreateServiceProvider();

        return serviceProvider;
    }

当我尝试发送这样的请求时：（在任何内容上设置 Accept 标头，例如“text/xml”）

我总是得到 200 OK - 使用“application/json”

我的 CountriesController 看起来像这样：

/// <summary>
/// REST API controller for actions with countries.
/// </summary>    
[AllowAnonymous]
[Area(Area.Common)]
[Route("[area]/Codebooks/[controller]")]
[ResponseCache(CacheProfileName = "CodebookCacheProfile")]
public class CountriesController : ApiController
{
    private readonly ICountryService countryService;

    /// <summary>
    /// Initializes a new instance of the <see cref="CountriesController" /> class.
    /// </summary>
    /// <param name="countryService">The country service.</param>
    public CountriesController(ICountryService countryService)
    {
        this.countryService = countryService ?? throw new ArgumentNullException(nameof(countryService));
    }

    /// <summary>
    /// Gets countries by search settings.
    /// </summary>
    /// <response code="200">The countries was returned correctly.</response>
    /// <response code="401">The unauthorized access.</response>
    /// <response code="406">The not acceptable format.</response>
    /// <response code="500">The unexpected error.</response>
    /// <param name="countrySearchSettings">The search settings of the country.</param>
    /// <returns>Data page of countries.</returns>        
    [HttpGet]
    [ProducesResponseType(typeof(IDataPage<Country>), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(void), StatusCodes.Status401Unauthorized)]
    [ProducesResponseType(typeof(void), StatusCodes.Status406NotAcceptable)]
    [ProducesResponseType(typeof(ApiErrorSummary), StatusCodes.Status500InternalServerError)]
    [SwaggerOperation("SearchCountries")]
    public IDataPage<Country> Get([FromQuery(Name = "")] CountrySearchSettings countrySearchSettings)
    {
        return countryService.Search(countrySearchSettings);
    }

    /// <summary>
    /// Gets a country.
    /// </summary>
    /// <response code="200">The country was returned correctly.</response>
    /// <response code="400">The country code is not valid.</response>
    /// <response code="401">The unauthorized access.</response>
    /// <response code="406">The not acceptable format.</response>
    /// <response code="500">The unexpected error.</response>
    /// <param name="countryCode">The code of the country.</param>
    /// <returns>Action result.</returns>   
    [HttpGet("{countryCode}")]
    [ProducesResponseType(typeof(Country), StatusCodes.Status200OK)]
    [ProducesResponseType(typeof(ApiValidationErrorSummary), StatusCodes.Status400BadRequest)]
    [ProducesResponseType(typeof(void), StatusCodes.Status401Unauthorized)]
    [ProducesResponseType(typeof(void), StatusCodes.Status406NotAcceptable)]
    [ProducesResponseType(typeof(ApiErrorSummary), StatusCodes.Status500InternalServerError)]
    [SwaggerOperation("GetCountry")]
    public IActionResult Get(string countryCode)
    {
        var country = countryService.GetByCode(countryCode);
        return Ok(country);
    }
}

你知道为什么请求 Accept 标头总是被忽略并且响应总是 200 OK 并且 Json 数据正确吗？ 我错过了什么？我认为 RespectBrowserAcceptHeader 和 ReturnHttpNotAcceptable 的设置可以做到这一点......但显然不是。 为什么总是回退到默认的 Json 格式化程序？

Answer 1

要使ReturnHttpNotAcceptable 工作，操作返回的类型必须是ObjectResult（例如Ok(retval)）或未实现IActionResult 的类型（在这种情况下，MVC 框架会将其包装在ObjectResult 给你）。

这是因为 MVC 框架仅在 ObjectResultExecutor 中检查 ReturnHttpNotAcceptable 的值，而不在任何其他 IActionResultExecutor 实现（如 ViewResultExecutor）中检查。 （参见ObjectResultExecutor和ViewResultExecutor的源代码）

简单地说，确保您返回的类型没有实现（或继承自任何实现的）IActionResult。

Answer 2

在 Startup.cs 的 ConfigureServices 方法中添加以下行

services.AddMvcCore().AddJsonFormatters().AddApiExplorer();