在ASP.NET 5中創建基於請求控制器/操作的格式化程序

Question

我正在嘗試在我的ASP rest API中實現HATEOAS，更改ReferenceResolverProvider 。

問題是，根據我使用的控制器，我想使用不同的ReferenceResolvers ，因為我需要為每個Controller表現不同。

現在我有通用的選擇：

services.AddMvc()
            .AddJsonOptions(option => option.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver())
            .AddJsonOptions(options => options.SerializerSettings.ReferenceResolverProvider = () => new RoomsReferenceResolver<Room>())
            .AddJsonOptions(options => options.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.Objects);

我想要這樣的東西：

services.AddMvc()
            .AddJsonOptions(option => option.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver())
            .AddJsonOptions<RoomsController>(options => options.SerializerSettings.ReferenceResolverProvider = () => new RoomsReferenceResolver<Room>())
            .AddJsonOptions(options => options.SerializerSettings.PreserveReferencesHandling = PreserveReferencesHandling.Objects);

Answer 1

您似乎想要創建一個每個控制器特定的格式化程序。 這可以通過使用名為IResourceFilter的過濾器來實現。 一個簡單的例子：

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class CamelCaseJsonFormatterResourceFilter : Attribute, IResourceFilter
{
    private readonly JsonSerializerSettings serializerSettings;

    public CamelCaseJsonFormatterResourceFilter()
    {
        // Since the contract resolver creates the json contract for the types it needs to deserialize/serialize,
        // cache it as its expensive
        serializerSettings = new JsonSerializerSettings()
        {
            ContractResolver = new CamelCasePropertyNamesContractResolver()
        };
    }

    public void OnResourceExecuted(ResourceExecutedContext context)
    {

    }

    public void OnResourceExecuting(ResourceExecutingContext context)
    {
        // remove existing input formatter and add a new one
        var camelcaseInputFormatter = new JsonInputFormatter(serializerSettings);
        var inputFormatter = context.InputFormatters.FirstOrDefault(frmtr => frmtr is JsonInputFormatter);
        if (inputFormatter != null)
        {
            context.InputFormatters.Remove(inputFormatter);
        }
        context.InputFormatters.Add(camelcaseInputFormatter);

        // remove existing output formatter and add a new one
        var camelcaseOutputFormatter = new JsonOutputFormatter(serializerSettings);
        var outputFormatter = context.OutputFormatters.FirstOrDefault(frmtr => frmtr is JsonOutputFormatter);
        if (outputFormatter != null)
        {
            context.OutputFormatters.Remove(outputFormatter);
        }
        context.OutputFormatters.Add(camelcaseOutputFormatter);
    }
}

// Here I am using the filter to indicate that only the Index action should give back a camelCamse response
public class HomeController : Controller
{
    [CamelCaseJsonFormatterResourceFilter]
    public Person Index()
    {
        return new Person() { Id = 10, AddressInfo = "asdfsadfads" };
    }

    public Person Blah()
    {
        return new Person() { Id = 10, AddressInfo = "asdfsadfads" };
    }

如果您對過濾器執行順序感到好奇，以下是它們序列的示例：

Inside TestAuthorizationFilter.OnAuthorization
Inside TestResourceFilter.OnResourceExecuting
Inside TestActionFilter.OnActionExecuting
Inside Home.Index
Inside TestActionFilter.OnActionExecuted
Inside TestResultFilter.OnResultExecuting
Inside TestResultFilter.OnResultExecuted
Inside TestResourceFilter.OnResourceExecuted

Answer 2

有趣的問題。

如何使ReferenceResolver成為一個門面：

    class ControllerReferenceResolverFacade : IReferenceResolver
    {
        private IHttpContextAccessor _context;

        public ControllerReferenceResolverFacade(IHttpContextAccessor context)
        {
            _context = context;
        }

        public void AddReference(object context, string reference, object value)
        {
          if ((string)_context.HttpContext.RequestServices.GetService<ActionContext>().RouteData.Values["Controller"] == "HomeController")
            {
                // pass off to HomeReferenceResolver
            }
            throw new NotImplementedException();
        }

然后你應該能夠做到：

services.AddMvc()
    .AddJsonOptions(options => options.SerializerSettings.ReferenceResolverProvider = () => {
        return new ControllerReferenceResolverFacade(
            services.BuildServiceProvider().GetService<IHttpContextAccessor>());
        });

這可能不是您需要的，但它可能會幫助您入門？