bgrebil / WebApi.Formatting.JsonMask

A JSON Mask Formatter for ASP.NET Web API

WebApi.Formatting.JsonMask

WebApi.Formatting.JsonMask provides a MediaTypeFormatter implementation for ASP.NET Web API that allows the user to specify specific parts of a JS object, hiding/masking the rest, thereby allowing the user to get a partial response.

To use the JsonMaskMediaTypeFormatter, add the following code to your Web API Configuration:

FormatterConfig.RegisterFormatters(GlobalConfiguration.Configuration.Formatters);

The FormatterConfig class looks this:

public class FormatterConfig
{
    public static void RegisterFormatters(MediaTypeFormatterCollection formatters)
    {
        var jsonFormatter = formatters.JsonFormatter;
        jsonFormatter.SerializerSettings = new JsonSerializerSettings {
            ContractResolver = new CamelCasePropertyNamesContractResolver()
        };

        // Insert the JsonMask formatter in front of the standard JSON formatter.
        var jsonMaskFormatter = new JsonMaskMediaTypeFormatter(formatters.JsonFormatter);
        formatters.Insert(0, jsonMaskFormatter);
    }
}

If you've used the Google APIs, and provided a ?fields= querystring to get a Partial Response, you've already used this language. The main difference is that this MediaTypeFormatter defaults to looking for a ?$fields= querystring field. If you wish to use something else, then you can specify it when creating the MediaTypeFormatter

var jsonMaskFormatter = new JsonMaskMediatypeFormatter(formatters.JsonFormatter, "fields");

Install

You can install through Nuget

Install-Package WebApi.Formatting.JsonMask    

Syntax

The syntax is loosely based on XPath:

• a,b,c comma-separated list will select multiple fields
• a/b/c path will select a field from its parent
• a(b,c) sub-selection will select many fields from a parent
• a/*/c the star * wildcard will select all items in a field

Examples

Identify the fields you want to keep

?$fields=name,address/zip

From this sample object:

{
   "name": "John Doe",
   "age": 32,
   "position": "programmer",
   "address": {
      "city": "Seattle",
      "state": "WA",
      "zip": "98101"
   }
}

You will get back:

{
   "name": "John Doe",
   "address": {
      "zip": "98101"
   }
}