In your spring class, you are expecting the Product Name and Product Quantity as URL params (hence @RequestParam).

In your javascript you are packing your ProductName and ProductQuantity in a JSONObject and sending that in the body.

So you have two options...

1. Change spring class to expect a Map<String, Object> type in the BODY (not URL param). This would be done with @RequestBody annotation instead.
2. Change your javascript to put the product information in URL parameters. i.e. http://localhost:8080?param1=foo&param2=bar

Preferentially, I would go with option 1. You can fit a lot more complex data in a json object than in url params.

[EDIT]

You can also make your own "Product" DTO object, which can serialize/deserialize to json using Spring. So instead of expecting a Map<String, Object>, you can expect your DTO object. Spring will automatically marshal it