mybatis foreach多次遍历问题:Error evaluating expression ‘’. Return value () was not iterable.

报错： org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.builder.BuilderException: Error evaluating expression ‘RNumList’. Return value (R1212340003) was not iterable.

出现这种错误：
Error evaluating expression ‘’’’. Return value () was not iterable

原因： mapper.xml文件中遍历List 时，该参数的实际值为非List数据。请仔细检查传入mybatis的参数类型。