通过一个简单的应用案例来说说迪米特法则

protected String convertResData(ExecuteContext executeContext) {
    if (Constant.SUCCESS.equals(executeContext.getResponseMessageVO().getResCode())) {
        return this.convertResData(executeContext.getResponseMessageVO().getResData());
    } else {
        if(BossKgConstant.ERROR_6216.equals(executeContext.getResponseMessageVO().getResCode())) {
            executeContext.getResponseMessageVO().setResCode(Constant.ERROR_6217);
        }
        if(BossKgConstant.ERROR_6221.equals(executeContext.getResponseMessageVO().getResCode())) {
            executeContext.getResponseMessageVO().setResCode(Constant.ERROR_6224);
        }
        if(BossKgConstant.ERROR_6222.equals(executeContext.getResponseMessageVO().getResCode())) {
            executeContext.getResponseMessageVO().setResCode(Constant.ERROR_6222);
        }
        if(BossKgConstant.ERROR_6223.equals(executeContext.getResponseMessageVO().getResCode())) {
            executeContext.getResponseMessageVO().setResCode(Constant.ERROR_6223);
        }
        return "";
    }
}

protected String convertResData(ResponseMessageVO responseMessageVO) {
    if (Constant.SUCCESS.equals(responseMessageVO.getResCode())) {
        return this.convertResData(responseMessageVO.getResData());
    } else {
        if (BossKgConstant.ERROR_6216.equals(responseMessageVO.getResCode())) {
            responseMessageVO.setResCode(Constant.ERROR_6217);
        }
        if (BossKgConstant.ERROR_6221.equals(responseMessageVO.getResCode())) {
            responseMessageVO.setResCode(Constant.ERROR_6224);
        }
        if (BossKgConstant.ERROR_6222.equals(responseMessageVO.getResCode())) {
            responseMessageVO.setResCode(Constant.ERROR_6222);
        }
        if (BossKgConstant.ERROR_6223.equals(responseMessageVO.getResCode())) {
            responseMessageVO.setResCode(Constant.ERROR_6223);
        }
        return "";
    }
}

@Service
@Slf4j
public class PaymentQueryBizService {
 
    @Autowired
    private RedisDistributedLock distributedLock;
 
    @Autowired
    private BankOrderFlowService bankOrderFlowService;
 
    @Autowired
    private PayErrorCodeService payErrorCodeService;
 
 
    public OrderPayStatusEnum paymentQuery(BankOrderFlow bankOrderFlow) {
        AssertUtil.notNull(bankOrderFlow.getFlowNo());  //              ②作为方法参数传入的对象的方法
 
        String key = ...;
        if (!distributedLock.lock(key, TimeUnit.MINUTES.toMillis(5))) {     //      ④对象持有的任何组件的方法
            throw BizException.build("获取分布式锁失败");
        }
 
        Map<String, String[]> map=new HashMap<>();
        map.put(...);               // ③该方法内部创建或实例化的对象的方法
 
        try {
            ...
 
            BankPayService bankPayService = StrategyManager.byStrategy(BankPayService.class, productSubTypeEnum);
 
            //查询通道
            PaymentTransQueryDTO paymentTransQueryDTO = bankPayService.payQuery(bankOrderFlow, channelConfig);  //       ③该方法内部创建或实例化的对象的方法
            //匹配错误码 如果命中则将订单置为失败
            if (!OrderPayStatusEnum.isFinalState(paymentTransQueryDTO.getOrderStatus())) {
                matchErrorCode(bankOrderFlow, paymentTransQueryDTO);            //          ①本对象自己的方法
            }
            return bankOrderFlowService.updateTransQueryResult(bankOrderFlow, paymentTransQueryDTO);    //  ④对象持有的任何组件的方法
        } finally {
            distributedLock.releaseLock(key);       //      ④对象持有的任何组件的方法
        }
    }
 
    private void matchErrorCode(BankOrderFlow bankOrderFlow, PaymentTransQueryDTO paymentTransQueryDTO) {
        ...
            
        log.info("交易查询-验证错误码-请求入参：{}", checkErrorCode);      //  是 ① 还是 ② 还是 ③ 还是 ④ ？
        CheckResult check = payErrorCodeService.check(checkErrorCode);      //      ④对象持有的任何组件的方法
        if (check.yes()) {
            paymentTransQueryDTO.setOrderStatus(FAIL);  //              ②作为方法参数传入的对象的方法
        }
    }
    
}