From 493881e31bbb9bb6abf9be43b37a63760c8cbf6f Mon Sep 17 00:00:00 2001
From: Administrator <15274802129@163.com>
Date: Mon, 03 Aug 2026 11:24:55 +0800
Subject: [PATCH] fix(mall): 修复优惠券金额分配计算精度问题
---
src/main/java/cc/mrbird/febs/mall/service/impl/ApiMallOrderInfoServiceImpl.java | 47 +++++++++++++++++++++++++++++++++++------------
1 files changed, 35 insertions(+), 12 deletions(-)
diff --git a/src/main/java/cc/mrbird/febs/mall/service/impl/ApiMallOrderInfoServiceImpl.java b/src/main/java/cc/mrbird/febs/mall/service/impl/ApiMallOrderInfoServiceImpl.java
index 1b46a1c..9ce3aa3 100644
--- a/src/main/java/cc/mrbird/febs/mall/service/impl/ApiMallOrderInfoServiceImpl.java
+++ b/src/main/java/cc/mrbird/febs/mall/service/impl/ApiMallOrderInfoServiceImpl.java
@@ -344,25 +344,48 @@
return couponAmountMap;
}
HashMap<Long,BigDecimal> skuMapPercent = new HashMap<>();//每个订单详情的ID和amount的map
+ Integer type = mallGoodsCoupon.getType();
+
+ // 计算总减免金额（满减类型需要先算满减次数）
+ BigDecimal totalDiscount;
+ if (MallGoodsCoupon.TYPE_TWO == type) {
+ BigDecimal divideTime = totalAmount.divide(costAmount, 0, BigDecimal.ROUND_DOWN);//累计减免次数
+ totalDiscount = divideTime.multiply(realAmount);//实际总减免金额
+ } else {
+ totalDiscount = realAmount;
+ }
+
+ // 记录每个SKU分配的减免金额，以及SKU金额最大的商品（用于修正精度损失）
+ BigDecimal allocatedDiscount = BigDecimal.ZERO;
+ Long maxAmountSkuId = null;
+ BigDecimal maxAmount = BigDecimal.ZERO;
+
for (Map.Entry<Long,BigDecimal> entry : skuMap.entrySet()) {
Long keySkuId = entry.getKey();
BigDecimal valueSkuAmount = entry.getValue();
BigDecimal divide = valueSkuAmount.divide(totalAmount, 4, BigDecimal.ROUND_DOWN);//每个商品占符合满减的总额的比例
skuMapPercent.put(keySkuId,divide);
- Integer type = mallGoodsCoupon.getType();
- if(MallGoodsCoupon.TYPE_ONE == type){
- BigDecimal bigDecimal = realAmount.multiply(divide).setScale(0, BigDecimal.ROUND_DOWN);//每个SKU的减免金额(比例*减免金额)
- BigDecimal skuRealAmount = valueSkuAmount.subtract(bigDecimal.compareTo(BigDecimal.ZERO) > 0 ? bigDecimal : BigDecimal.ZERO);//实际支付金额
- couponAmountMap.put(keySkuId,skuRealAmount);
- }
- if(MallGoodsCoupon.TYPE_TWO == type){
- BigDecimal divideTime = totalAmount.divide(costAmount, 0, BigDecimal.ROUND_DOWN);//累计减免次数
- BigDecimal multiply = divideTime.multiply(realAmount);//实际减免金额
- BigDecimal bigDecimal = multiply.multiply(divide).setScale(0, BigDecimal.ROUND_DOWN);//每个SKU的减免金额(比例*实际减免金额)
- BigDecimal skuRealAmount = valueSkuAmount.subtract(bigDecimal.compareTo(BigDecimal.ZERO) > 0 ? bigDecimal : BigDecimal.ZERO);//实际支付金额
- couponAmountMap.put(keySkuId,skuRealAmount);
+
+ // 直接用 (总折扣 × 商品金额) / 总金额 计算，避免比例中间舍入导致精度丢失
+ BigDecimal itemDiscount = totalDiscount.multiply(valueSkuAmount).divide(totalAmount, 0, BigDecimal.ROUND_DOWN);//每个SKU的减免金额
+ BigDecimal skuRealAmount = valueSkuAmount.subtract(itemDiscount.compareTo(BigDecimal.ZERO) > 0 ? itemDiscount : BigDecimal.ZERO);//实际支付金额
+ couponAmountMap.put(keySkuId, skuRealAmount);
+ allocatedDiscount = allocatedDiscount.add(itemDiscount);
+
+ // 记录金额最大的SKU，用于后续修正精度损失
+ if (valueSkuAmount.compareTo(maxAmount) > 0) {
+ maxAmount = valueSkuAmount;
+ maxAmountSkuId = keySkuId;
}
}
+
+ // 修正精度损失：ROUND_DOWN导致分配的减免金额可能小于总减免金额，将差额补到金额最大的商品上
+ BigDecimal diff = totalDiscount.subtract(allocatedDiscount);
+ if (diff.compareTo(BigDecimal.ZERO) > 0 && maxAmountSkuId != null) {
+ BigDecimal oldAmount = couponAmountMap.get(maxAmountSkuId);
+ couponAmountMap.put(maxAmountSkuId, oldAmount.subtract(diff));
+ }
+
return couponAmountMap;
}
--
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