Spring Boot Rest Controller how to return different HTTP status codes?

There are several options you can use. Quite good way is to use exceptions and class for handling called @ControllerAdvice:

@ControllerAdvice
class GlobalControllerExceptionHandler {
    @ResponseStatus(HttpStatus.CONFLICT)  // 409
    @ExceptionHandler(DataIntegrityViolationException.class)
    public void handleConflict() {
        // Nothing to do
    }
}

Also you can pass HttpServletResponse to controller method and just set response code:

public RestModel create(@RequestBody String data, HttpServletResponse response) {
    // response committed...
    response.setStatus(HttpServletResponse.SC_ACCEPTED);
}

Please refer to the this great blog post for details: Exception Handling in Spring MVC

NOTE

In Spring MVC using @ResponseBody annotation is redundant – it’s already included in @RestController annotation.