Retrieve query string parameters in Spring Boot

Use @RequestParam

@RequestMapping(method = RequestMethod.GET)
public @ResponseBody item getitem(@RequestParam("data") String itemid){

    item i = itemDao.findOne(itemid);              
    String Itemname=i.getItemname();
    String price= i.getPrice();
    return i;
}

Making an Optional Request Parameter

@GetMapping("/api/foos")
@ResponseBody
public String getFoos(@RequestParam(required = false) String id) { 
    return "ID: " + id;
}

References
https://stackoverflow.com/questions/32201441/how-do-i-retrieve-query-parameters-in-spring-boot
https://www.baeldung.com/spring-request-param