$与#的区别
select * from T_PRINT_LAYOUT where D_RECID = ${recId}
最后生成的SQL为：
select * from T_PRINT_LAYOUT where D_RECID = 1
即：直接将参数值替换到了原来${recId}的位置，相当于硬拼SQL
select * from T_PRINT_LAYOUT where D_RECID = #{recid,jdbcType=DECIMAL}
最后生成的SQL为：
select * from T_PRINT_LAYOUT where D_RECID = ?
即：#{...}被识别为一个SQL参数
原文：https://www.cnblogs.com/jagng951014/p/9462462.html