How to change default Web API 2 to JSON formatter?

Question

I have a Web API project that returns some product data. It negotiates the return type correctly depending on the Accept header (JSON/XML) of the request. The problem is, if no Accept header is specified it returns XML, but I want it to return JSON by default

http://website.com/MyPage?type=json // returns json
http://website.com/MyPage?type=xml // returns xml
http://website.com/MyPage // returns xml by default

Here is my current code looks like:

GlobalConfiguration.Configuration.Formatters.XmlFormatter.MediaTypeMappings.Add(
new QueryStringMapping("type", "xml", new MediaTypeHeaderValue("application/xml")));

GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(
new QueryStringMapping("type", "json", new MediaTypeHeaderValue("application/json")));

Triet Doan · Answer 1 · 2016-07-14T15:15:23.907

28

Add this in your App_Start/WebApiConfig.cs:

config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("text/html"));

edited Jul 14 '16 at 15:15

answered Jul 03 '15 at 10:49

Triet Doan

11,455
8
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1

When using Owin you need to use to the `config` object created in `WebApiConfig.Register()` with `new Httpconfiguration()`, and not `GlobalConfiguration.Configuration` More information [here](https://stackoverflow.com/questions/28552567/web-api-2-how-to-return-json-with-camelcased-property-names-on-objects-and-the/31951291#31951291) – Alastair Feb 02 '17 at 14:30
Here is a link to [my answer below](http://stackoverflow.com/questions/25224824/how-to-change-default-web-api-2-to-json-formatter/42005182#42005182) which I include because I had to tear all my hair out to get this to work and hope to save someone the pain. – Alastair Feb 02 '17 at 14:48
@Alastair, thank you for your contribution :). And downvoter, please be kind to leave a comment when you downvote someone. – Triet Doan Feb 02 '17 at 23:48

score 16 · Answer 2 · answered Aug 10 '14 at 07:16

I think Web API just uses the first formatter it can find in the Formatters collection. You can change the ordering with something like

GlobalConfiguration.Configuration.Formatters.Clear();
GlobalConfiguration.Configuration.Formatters.Add(new JsonMediaTypeFormatter());
GlobalConfiguration.Configuration.Formatters.Add(new XmlMediaTypeFormatter());

But it seems the JSON formatter should be the first one by default so you might want to check if you're already modifying this collection somewhere.

score 8 · Answer 3 · edited Sep 07 '18 at 10:55

I think you should change as following. Global.asax:

/*For Indented formatting:*/       
 GlobalConfiguration.Configuration.Formatters.JsonFormatter.SerializerSettings.Formatting = Newtonsoft.Json.Formatting.Indented;

    /*Response as default json format
     * example (http://localhost:9090/WebApp/api/user/)
     */
    GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();

    /*Response as json format depend on request type
     * http://localhost:9090/WebApp/api/user/?type=json
     */
    GlobalConfiguration.Configuration.Formatters.JsonFormatter.MediaTypeMappings.Add(
    new QueryStringMapping("type", "json", new MediaTypeHeaderValue("application/json")));

    /*Response as xml format depend on request type
     * http://localhost:9090/WebApp/api/user/?type=xml
     */
    GlobalConfiguration.Configuration.Formatters.XmlFormatter.MediaTypeMappings.Add(
    new QueryStringMapping("type", "xml", new MediaTypeHeaderValue("application/xml")));

score 5 · Answer 4 · answered Dec 16 '15 at 11:48

5

Or just remove the XmlFormatter

var formatters = GlobalConfiguration.Configuration.Formatters;
formatters.Remove(formatters.XmlFormatter);

answered Dec 16 '15 at 11:48

Alex

158
2
7

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Those strings must be added to your Application_Start() in Global.asax as described in official docs http://www.asp.net/web-api/overview/formats-and-model-binding/json-and-xml-serialization#json_media_type_formatter – Deepscorn Feb 07 '16 at 02:46

score 4 · Answer 5 · answered Feb 02 '17 at 14:46

None of the above answers worked for me. The problem was that I was getting hold of the formatters from GlobalConfiguration and not the config object created with new HttpConfiguration() Here is the code that works for me :

public class WebApiConfig
{
    public static HttpConfiguration Register()
    {

        var config = new HttpConfiguration();
        // This next line could stay if you want xml formatting
        config.Formatters.Remove(config.Formatters.XmlFormatter);

        // This next commented out line was causing the problem
        //var jsonFormatter = GlobalConfiguration.Configuration.Formatters.JsonFormatter;

        // This next line was the solution
        var jsonFormatter = config.Formatters.JsonFormatter;
        jsonFormatter.UseDataContractJsonSerializer = false; // defaults to false, but no harm done
        jsonFormatter.SerializerSettings.DateFormatHandling = DateFormatHandling.IsoDateFormat;
        jsonFormatter.SerializerSettings.Formatting = Formatting.None;
        jsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();           

        // remaining irrelevant code commented out
        return config;
    }
}

score 1 · Answer 6 · answered Jul 15 '20 at 23:28

FYI be careful of intercepting the text/html media type because this will also format the 404 responses from your server. And in my case, this led to a potential security issue because:

malicious user browses to http://api.mysite.com/one/two?test=%3Cscript%3Ealert(%27hi%27)%3C/script%3E
Web API returns the 404 object, which includes the URL. This is in JSON format because of the attribute above.
Browser thinks the returned object is actually text/html, so it just renders the JSON object
This causes the script tag embedded in the URL to execute. In my example URL above it is just an alert, but it could also be a window.location or anything sinister

score 0 · Answer 7 · edited May 09 '17 at 00:40

config.EnableSystemDiagnosticsTracing();

GlobalConfiguration.Configuration.Formatters.XmlFormatter.SupportedMediaTypes.Clear();

// Adding formatter for Json   
config.Formatters.JsonFormatter.MediaTypeMappings.Add(new QueryStringMapping("type", "json", new MediaTypeHeaderValue("application/json")));

// Adding formatter for XML   
config.Formatters.XmlFormatter.MediaTypeMappings.Add(new QueryStringMapping("type", "xml", new MediaTypeHeaderValue("application/xml")));

How to change default Web API 2 to JSON formatter?

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