Defining an API with swagger: GET call that uses JSON in parameters

Question

I am trying to create a proper, REST API, and document it with Swagger (2.0).

So, I have an API call that is a query, ie, it makes no changes and doesn\'t create any

Answer 1

For .Net and Swashbuckle (tested on 3.0) I have a generic class JsonModelBinder that implements IModelBinder interface. The class is used like this:

public IActionResult SomeAction(
        [FromRoute] int id, 
        [FromQuery][ModelBinder(BinderType = typeof(JsonModelBinder))] SomeModelquery query) => {}

I have created Operation filter that does the following:

• Removes parameters created by Swashbuckle from properties of my model
• Add query parameter of type string

As a result in Swagger I have a text field where I can insert json and test requests

public class JsonModelBinderOperationFilter : IOperationFilter
{
    public void Apply(Operation operation, OperationFilterContext context)
    {
        if (operation.Parameters == null || context.ApiDescription.HttpMethod != HttpMethod.Get.ToString())
            return;
        //Find json parameters
        var jsonGetParameters = context.ApiDescription.ActionDescriptor.Parameters.Cast()
            .Where(p => p.ParameterInfo.CustomAttributes.Any(c => c.AttributeType == typeof(ModelBinderAttribute) && c.NamedArguments.Any(IsJsonModelBinderType))).ToArray();

        if (jsonGetParameters.Length > 0)
        {
            //Select parameters names created by Swagger from json parameters
            var removeParamNames = new HashSet(context.ApiDescription.ParameterDescriptions.Where(d => jsonGetParameters.Any(p => p.Name == d.ParameterDescriptor.Name)).Select(p => p.Name));
            //Create new Swagger parameters from json parameters
            var newParams = jsonGetParameters.Select(p => new NonBodyParameter()
            {
                In = "query",
                Name = p.Name,
                Type = "string",
                Description = "Json representation of " + p.ParameterType.Name
            });
            //Remove wrong parameters and add new parameters
            operation.Parameters = operation.Parameters.Where(p => p.In != "query" || !removeParamNames.Contains(p.Name)).Concat(newParams).ToList();
        }
    }

    private static bool IsJsonModelBinderType(CustomAttributeNamedArgument arg)
    {
        var t = arg.TypedValue.Value as Type;
        return t != null && t.GetGenericTypeDefinition().IsAssignableFrom(typeof(JsonModelBinder<>));
    }
}

Notes:

• I use IsAssignableFrom because I have classes derived from JsonModelBinder. You can omit it if you don't inherit
• You can also omit GetGenericTypeDefinition if your binder is not generic
• This solution doesn't check for parameter name collision, though you should never have it if the API made with common sense