springboot @Value 类中读取配置文件 .properties null 原因和解决方案

问题：在一个工具类中，通过@Value来映射配置文件的值，得到的总是null

原因：不能用new工具类的方式，应该是用容器注册（@Autowried）的方式使用此工具类，就能得到配置文件里的值

上代码：

工具类：

package com.***.***.utils;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import system.Decimal;

import java.math.BigDecimal;

@Component
public class RoundCalculationUtil {

    @Value("${***.round.calculation}")
    private String calculationWay;

    public BigDecimal reCalculateAmount(BigDecimal amount){
        if(calculationWay.equals("currencyround")){
            return currencyRound(amount);
        }else {
            return round(amount);
        }
    }

    public BigDecimal round(BigDecimal amount) {
        BigDecimal result = amount.setScale(0, BigDecimal.ROUND_DOWN);
        BigDecimal lastRound2 = amount.setScale(2, BigDecimal.ROUND_DOWN).subtract(result);
        if (lastRound2.compareTo(new BigDecimal("0.50")) >= 0) {
            result = result.add(new BigDecimal("1"));
        }

        return result;
    }

    public BigDecimal currencyRound(BigDecimal amount){
        BigDecimal result = amount.setScale(2,BigDecimal.ROUND_DOWN);
        BigDecimal firstRound4=amount.setScale(4,BigDecimal.ROUND_DOWN);
        BigDecimal lastRound2=firstRound4.subtract(firstRound4.setScale(2,BigDecimal.ROUND_DOWN));
        if(lastRound2.compareTo(new BigDecimal("0.0005"))>=0){
            result=result.add(new BigDecimal("0.01"));
        }
        return result;
    }

}

调用处：

@Autowired
    RoundCalculationUtil roundCalculationUtil;

    @RequestMapping(value = "/roundtest", method = RequestMethod.GET)
    public ResponseData<String> roundTest(@RequestParam(value = "amount", required = true, defaultValue = "100.1111") BigDecimal amount,
             @RequestParam(value = "roundcalculation", required = false, defaultValue = "currencyround") String roundcalculation) {
        try {
            BigDecimal result=roundCalculationUtil.reCalculateAmount(amount);
        
            //BigDecimal result=new RoundCalculationUtil ().reCalculateAmount(amount);//will get null from .properties file

            DecimalFormat df = new DecimalFormat("0.00");
            return new ResponseData(NotificationMsg.SUCCESS, df.format(result));
        } catch (Exception e) {
            logger.error(e);
            return new ResponseData(NotificationMsg.FAILED, e);
        }

    }