商城：完善购物车的逻辑

yudao-framework/yudao-spring-boot-starter-mybatis/src/main/java/cn/iocoder/yudao/framework/mybatis/core/mapper/BaseMapperX.java

@@ -46,6 +46,18 @@ public interface BaseMapperX<T> extends MPJBaseMapper<T> {
         return selectOne(new LambdaQueryWrapper<T>().eq(field1, value1).eq(field2, value2));
     }
 
+    default T selectOne(SFunction<T, ?> field1, Object value1, SFunction<T, ?> field2, Object value2,
+                        SFunction<T, ?> field3, Object value3) {
+        return selectOne(new LambdaQueryWrapper<T>().eq(field1, value1).eq(field2, value2)
+                .eq(field3, value3));
+    }
+
+    default T selectOne(SFunction<T, ?> field1, Object value1, SFunction<T, ?> field2, Object value2,
+                        SFunction<T, ?> field3, Object value3, SFunction<T, ?> field4, Object value4) {
+        return selectOne(new LambdaQueryWrapper<T>().eq(field1, value1).eq(field2, value2)
+                .eq(field3, value3).eq(field4, value4));
+    }
+
     default Long selectCount() {
         return selectCount(new QueryWrapper<T>());
     }