Pasted

контроллер:
 @RestController
public class NewsController {
     @GetMapping("/data/test")
    public String test(
            @RequestParam(name="id_binding", required = false) Integer idBinding
    ) {
        return "ok";
    }
}
   открываю в браузере:
http://localhost:9050/data/test?id_binding=null
  ошибка:
There was an unexpected error (type=Bad Request, status=400).
Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "null"
  консоль:
2018-11-18 20:19:27.479  WARN 26864 --- [nio-9050-exec-6] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved exception caused by Handler execution: org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.lang.Integer'; nested exception is java.lang.NumberFormatException: For input string: "null"
    а так работает:
http://localhost:9050/data/test?id_binding=1