org.mybatis.spring.MyBatisSystemException: nested exception is org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'com.myproject.community.dao.DiscussPostMapper.selectDiscussPostRows'. It's likely that neither a Result Type nor a Result Map was specified.
查询的时候缺少了入参或出参
当存在<if>时，即使是java自带的类型，也需要加返回值类型。其他情况，只有在使用的bean是加就可以，即不是java自带类型。