创建 CartService.java

src/main/java/com/gao/finalhw/service/CartService.java

@@ -0,0 +1,17 @@
+package com.gao.finalhw.service;
+
+import com.gao.finalhw.mapper.ShoppingCartMapper;
+import com.gao.finalhw.model.ShoppingCart;
+import org.apache.ibatis.annotations.Mapper;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+@Service
+public class CartService {
+    @Autowired
+    ShoppingCartMapper shoppingCartMapper;
+    public int getCartCount(int id){
+        ShoppingCart result = shoppingCartMapper.selectById(id);
+        return  result.getCartId();
+    }
+}