consuming JSON POST data in an Express application

I am sending this JSON file to my node js server :

{
"try": "this"
}

I sent it using Postman (chrome extension) like this:

I'm trying to log this data from the server, I am using node js & express framework. In the main app.js I used:

app.use(express.urlencoded());
app.use(express.json());
app.post('/update/:id', app_object.update);

And in the app_object router:

exports.update = function ( req, res, next ){
    var postedObject = req.body;
    console.log(postedObject);
    res.send('Handle Post');
};

When I send the Post request I am getting from the server only '{}'. Can someone explain what's wrong? Thanks.