ASP.NET Core handling JSON deserialization problems

问题

I would like to change default behavior of invalid JSON request handling in ASP.NET Core. I have this model:

public class Model
{
    public Guid Id { get; set; }
}

And when I send this request with this body

{
 "Id": null
}

It returns this error message:

 "Error converting value {null} to type 'System.Guid'. Path 'Id', line 2, position 11."

Of course this is absolutely logical but I want Id to be set to default value (Guid.Empty) instead of failing request. I have added this json config in Startup:

services.AddMvc()
            .AddJsonOptions(options => options.SerializerSettings.Error = (a, e) =>
            {
                e.ErrorContext.Handled = true;
            })

Error handler is being hit however ASP.NET Core still returns failure. This in different behavior compared to ASP.NET Web API where this was possible.

回答1:

As you have found, this behavior is handled by JsonInputFormatter, you could custom the formatter to override this behavior like

1. IgnoreGuidErrorJsonInputFormatter

   public class IgnoreGuidErrorJsonInputFormatter : JsonInputFormatter
   {
       public IgnoreGuidErrorJsonInputFormatter(ILogger logger, JsonSerializerSettings serializerSettings, ArrayPool<char> charPool, ObjectPoolProvider objectPoolProvider, MvcOptions options, MvcJsonOptions jsonOptions) : base(logger, serializerSettings, charPool, objectPoolProvider, options, jsonOptions)
       {
           serializerSettings.Error = (a, e) =>
           {
               var errors = e.ErrorContext.Error;
               e.ErrorContext.Handled = true;
           };
       }
   }
   

2. Register IgnoreGuidErrorJsonInputFormatter

   services.AddMvc(options =>
   {
       var serviceProvider = services.BuildServiceProvider();
       var customJsonInputFormatter = new IgnoreGuidErrorJsonInputFormatter(
                   serviceProvider.GetRequiredService<ILoggerFactory>().CreateLogger<IgnoreGuidErrorJsonInputFormatter>(),
                   serviceProvider.GetRequiredService<IOptions<MvcJsonOptions>>().Value.SerializerSettings,
                   serviceProvider.GetRequiredService<ArrayPool<char>>(),
                   serviceProvider.GetRequiredService<ObjectPoolProvider>(),
                   options,
                   serviceProvider.GetRequiredService<IOptions<MvcJsonOptions>>().Value
           );
       options.InputFormatters.Insert(0, customJsonInputFormatter);
   });
   

来源：https://stackoverflow.com/questions/58018207/asp-net-core-handling-json-deserialization-problems