org.postgresql.util.PSQLException: ERROR: syntax error at or near “$1“的解决办法

mapper.xml中定义的postgre SQL语句运行时报错：org.postgresql.util.PSQLException: ERROR: syntax error at or near “$1“

SELECT * from m_user where resigndt >= now()- INTERVAL #{flag} and resigndt <= now();

是数据转换异常(例如：Integer和String间转换异常) ，

解决方法1.将#改成$，$可转换成数值类型，但是使用$无法防止Sql注入

解决办法2. 将 INTERVAL #{flag} 替换成 #{flag}::INTERVAL
SELECT * from m_user where resigndt >= now()- #{flag}::INTERVAL and resigndt <= now()