Step 1: Migration SQL  → 建表，定义数据模型
Step 2: Entity         → 映射表结构到 Java 类
Step 3: Mapper         → 空接口，继承 BaseMapper
Step 4: DTOs           → 请求/响应对象
Step 5: Converter      → MapStruct Entity ↔ DTO 转换
Step 6: Service 接口   → 定义业务方法签名
Step 7: Service 实现   → 实现业务逻辑
Step 8: Facade         → 跨服务编排、事务管理
Step 9: Controller     → HTTP 入口、参数校验

project/
├── {service-module}/src/main/java/com/example/service/
│   ├── entity/           # Step 2
│   ├── repository/       # Step 3 (Mapper)
│   ├── dto/
│   │   └── {module}/     # Step 4
│   ├── converter/        # Step 5
│   └── service/
│       └── impl/         # Step 6-7
├── {web-module}/src/main/java/com/example/web/
│   ├── facade/           # Step 8
│   └── controller/       # Step 9
└── migrations/{module}/scripts/  # Step 1

@Data
@EqualsAndHashCode(callSuper = true)
@TableName("alert_policy")
public class AlertPolicy extends BizEntity {
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;

    @TableField("name")
    private String name;

    // 枚举字段
    @TableField("status")
    private PolicyStatusEnum status;

    // JSON 字段
    @TableField(value = "config_json", typeHandler = JacksonTypeHandler.class)
    private Map<String, Object> configJson;

    // 逻辑删除
    @TableLogic
    private Boolean deleted;
}

@Mapper
public interface AlertPolicyMapper extends BaseMapper<AlertPolicy> {
    // 空接口 - 不添加任何方法
}

// 接口
public interface PolicyService {
    AlertPolicy getById(Long id);
    Long create(PolicyCreateReq req);
    void update(Long id, PolicyUpdateReq req);
    void delete(Long id);
    PageResult<PolicyCard> getPage(int page, int size, String name);
}

// 实现
@Slf4j
@Service
@RequiredArgsConstructor
public class PolicyServiceImpl implements PolicyService {
    private final AlertPolicyMapper policyMapper;
    private final PolicyConverter converter;

    @Override
    public AlertPolicy getById(Long id) {
        AlertPolicy entity = policyMapper.selectById(id);
        if (entity == null) {
            throw new BusinessException(ErrorCode.POLICY_NOT_FOUND, "策略不存在: " + id);
        }
        return entity;
    }

    @Override
    @Transactional(rollbackFor = Exception.class)
    public Long create(PolicyCreateReq req) {
        validateNameUnique(req.getName(), null);
        AlertPolicy entity = converter.toEntity(req);
        entity.setStatus(PolicyStatusEnum.DISABLED);
        policyMapper.insert(entity);
        return entity.getId();
    }
}

@Component
@Slf4j
@RequiredArgsConstructor
public class PolicyFacade {
    private final PolicyService policyService;
    private final TaskService taskService;  // 可注入多个 Service

    @Transactional(rollbackFor = Exception.class)
    public Long create(PolicyCreateReq req) {
        return policyService.create(req);
    }

    // 读操作：查询 + 丰富关联数据
    public PolicyDetail getDetail(Long id) {
        PolicyDetail detail = policyService.getDetail(id);
        // 丰富关联数据
        enrichWithRelatedData(detail);
        return detail;
    }
}