黑马程序员：在技术的荒野上，做一匹不认命的孤狼

// 问题代码：ThreadLocal未及时清理导致内存泄露
public class UserContextHolder {
    private static final ThreadLocal<User> currentUser = new ThreadLocal<>();
    
    public static void set(User user) {
        currentUser.set(user);
    }
    
    // 遗忘的清理方法！每次请求结束后应该调用
    public static void clear() {
        currentUser.remove();
    }
}

import logging
from typing import Optional
from retry import retry

logger = logging.getLogger(__name__)

class PaymentService:
    def __init__(self, third_party_gateway, max_retries: int = 3):
        self.gateway = third_party_gateway
        self.max_retries = max_retries
    
    @retry(tries=3, delay=1, backoff=2, exceptions=(ConnectionError, TimeoutError))
    def charge(self, user_id: str, amount: int) -> dict:
        """
        执行扣款操作
        - user_id: 用户标识
        - amount: 金额（单位：分）
        """
        if amount <= 0:
            raise ValueError("扣款金额必须大于0")
        
        try:
            # 调用第三方支付网关
            result = self.gateway.submit_payment(user_id, amount)
            
            # 即使网关返回成功，也要校验签名和金额一致性
            if not self._verify_signature(result):
                logger.error(f"支付回调签名校验失败: {result}")
                raise SecurityException("支付结果签名被篡改")
            
            if result['actual_amount'] != amount:
                # 金额不一致，必须人工介入
                logger.critical(f"金额不一致: 预期{amount}, 实际{result['actual_amount']}, user={user_id}")
                self._alert_ops_team(user_id, amount, result)
                raise AmountMismatchException("支付金额与请求金额不符")
            
            return result
            
        except (ConnectionError, TimeoutError) as e:
            # 网络类异常由@retry自动重试，此处只记录
            logger.warning(f"支付接口网络异常, user={user_id}, error={e}")
            raise  # 让retry装饰器捕获
        except Exception as e:
            # 其他未知异常，直接记录并抛出业务异常
            logger.error(f"支付过程未知异常, user={user_id}", exc_info=True)
            raise PaymentFailedException(f"支付处理失败: {str(e)}")
    
    def _verify_signature(self, result: dict) -> bool:
        # 签名验证逻辑
        pass
    
    def _alert_ops_team(self, user_id, amount, result):
        # 发送钉钉/企微报警
        pass

# 黑马风格的文件操作：显式声明编码，处理细粒度异常，用with管理资源
from pathlib import Path

def load_config(config_path: str) -> dict:
    path = Path(config_path)
    if not path.exists():
        raise FileNotFoundError(f"配置文件不存在: {config_path}")
    if not path.is_file():
        raise IsADirectoryError(f"路径指向目录而非文件: {config_path}")
    
    try:
        content = path.read_text(encoding='utf-8')
        # 这里会处理JSON解析异常
        return json.loads(content)
    except json.JSONDecodeError as e:
        raise ConfigFormatError(f"配置文件JSON格式错误: {e}") from e
    except PermissionError as e:
        raise ConfigAccessError(f"无权限读取配置文件: {e}") from e