当使用Map做为参数时，可以用_parameter.containsKey(变量名)来判断map中是否包含有些变量：

  

      SELECT ruleId,msgType,event,respId,reqValue,firstRespId,createDate,yn      FROM oal_tb_rule      WHERE yn = 1                AND msgType = #{msgType,jdbcType=VARCHAR})                      AND event = #{event,jdbcType=VARCHAR})