feat(pricing): 优化优惠券领取逻辑与并发控制

- 为 CouponInvalidException 添加错误码支持
- 在 countUserCouponClaims 查询中添加 FOR UPDATE 锁
- 新增 incrementClaimedQuantityIfAvailable 方法用于原子性增加已领取数量
- 移除重复的用户优惠券领取检查逻辑
- 调整领取流程步骤编号并优化事务回滚处理
- 增加对优惠券库存耗尽情况的业务异常处理
- 使用

src/main/java/com/ycwl/basic/pricing/service/impl/CouponServiceImpl.java

@@ -18,6 +18,7 @@ import java.util.Date;
 import lombok.extern.slf4j.Slf4j;
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
+import org.springframework.transaction.interceptor.TransactionAspectSupport;
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
@@ -243,6 +244,7 @@ public class CouponServiceImpl implements ICouponService {
             if (coupon.getUserClaimLimit() != null && coupon.getUserClaimLimit() > 0) {
                 int userClaimCount = couponClaimRecordMapper.countUserCouponClaims(
                         request.getUserId(), request.getCouponId());
+                // countUserCouponClaims 使用 FOR UPDATE + 复合索引，确保并发下的计数准确
                 if (userClaimCount >= coupon.getUserClaimLimit()) {
                     return CouponClaimResult.failure(
                             CouponClaimResult.ERROR_CLAIM_LIMIT_REACHED,
@@ -250,14 +252,7 @@ public class CouponServiceImpl implements ICouponService {
                 }
             }
 
-            // 7. 检查用户是否已经领取过该优惠券（兼容旧逻辑，双重保护）
-            PriceCouponClaimRecord existingRecord = couponClaimRecordMapper.selectUserCouponRecord(
-                    request.getUserId(), request.getCouponId());
-            if (existingRecord != null) {
-                return CouponClaimResult.failure(CouponClaimResult.ERROR_ALREADY_CLAIMED, "您已经领取过该优惠券");
-            }
-
-            // 8. 创建领取记录
+            // 7. 创建领取记录
             Date claimTime = new Date();
             PriceCouponClaimRecord claimRecord = new PriceCouponClaimRecord();
             claimRecord.setCouponId(request.getCouponId());
@@ -269,7 +264,7 @@ public class CouponServiceImpl implements ICouponService {
             claimRecord.setUpdateTime(claimTime);
             claimRecord.setDeleted(0);
 
-            // 9. 插入领取记录
+            // 8. 插入领取记录
             int insertResult = couponClaimRecordMapper.insert(claimRecord);
             if (insertResult <= 0) {
                 log.error("插入优惠券领取记录失败: userId={}, couponId={}",
@@ -277,24 +272,38 @@ public class CouponServiceImpl implements ICouponService {
                 return CouponClaimResult.failure(CouponClaimResult.ERROR_SYSTEM_ERROR, "领取失败，请稍后重试");
             }
 
-            // 10. 更新优惠券已领取数量（区分于已使用数量）
+            // 9. 更新优惠券已领取数量（区分于已使用数量）
             // 仅在有总量限制时才更新claimedQuantity(totalQuantity为正整数)
             if (coupon.getTotalQuantity() != null && coupon.getTotalQuantity() > 0) {
+                int affected = couponConfigMapper.incrementClaimedQuantityIfAvailable(coupon.getId());
+                if (affected == 0) {
+                    throw new CouponInvalidException(
+                            CouponClaimResult.ERROR_COUPON_OUT_OF_STOCK,
+                            "优惠券已被领取完，请稍后重试");
+                }
                 int updatedClaimedQuantity = (coupon.getClaimedQuantity() == null ? 0 : coupon.getClaimedQuantity()) + 1;
                 coupon.setClaimedQuantity(updatedClaimedQuantity);
-                couponConfigMapper.updateById(coupon);
             }
 
             log.info("优惠券领取成功: userId={}, couponId={}, claimRecordId={}",
                     request.getUserId(), request.getCouponId(), claimRecord.getId());
 
-            // 11. 返回成功结果
+            // 10. 返回成功结果
             return CouponClaimResult.success(claimRecord, coupon);
             
+        } catch (CouponInvalidException e) {
+            TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
+            log.warn("领取优惠券失败(业务校验不通过): userId={}, couponId={}, reason={}",
+                    request.getUserId(), request.getCouponId(), e.getMessage());
+            String errorCode = e.getErrorCode() == null
+                    ? CouponClaimResult.ERROR_SYSTEM_ERROR
+                    : e.getErrorCode();
+            return CouponClaimResult.failure(errorCode, e.getMessage());
         } catch (Exception e) {
-            log.error("领取优惠券失败: userId={}, couponId={}", 
+            TransactionAspectSupport.currentTransactionStatus().setRollbackOnly();
+            log.error("领取优惠券失败: userId={}, couponId={}",
                     request.getUserId(), request.getCouponId(), e);
             return CouponClaimResult.failure(CouponClaimResult.ERROR_SYSTEM_ERROR, "系统错误，领取失败：" + e.getMessage());
         }
     }
-}
+}