The @RestController annotation

@RestController is a class-level annotation used for the resource class introduced in Spring 4. It is a combination of @Controller and @ResponseBody, and because of it, a class returns a domain object instead of a view.

In the following code, you can see that the CalculationController class handles GET requests for /calculation by returning a new instance of the calculation class.

We will implement two URIs for a Calculation resource—the square root (Math.sqrt() function) as the /calculations/sqrt URI, and power (Math.pow() function) as the /calculation/power URI.