mybatis @Select注解中如何拼写动态sql

package cn.erongcai.hrplatform.dao.demand;import java.util.List;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.annotations.Param;import org.apache.ibatis.annotations.Select;import com.baomidou.mybatisplus.mapper.BaseMapper;import cn.erongcai.hrplatform.model.demand.DemandComment;@Mapperpublic interface DemandCommentMapper extends BaseMapper<DemandComment>{@Select("SELECT "+ "a.id as 'id',a.create_date as 'createDate',a.content as 'content',"+ "a.parent_id as 'parentId',a.first_comment_id as 'firstCommentId',"+ "b.id as 'fromUser.id',b.realname as 'fromUser.realname',b.avatar as 'fromUser.avatar',"+ "c.id as 'toUser.id',c.realname as 'toUser.realname',c.avatar as 'toUser.avatar' "+ "FROM t_demand_comment a "+ "LEFT JOIN t_user b ON b.id = a.from_uid "+ "LEFT JOIN t_user c ON c.id = a.to_uid "+ "WHERE a.demand_id = #{demandId} "+ "ORDER BY a.create_date ASC"+ "LIMIT #{startNo},#{pageSize}")public List<DemandComment> listDemandComment(@Param("demandId") Long demandId, @Param("startNo") Integer pageNo, @Param("pageSize") Integer pageSize);}

这样整个语句是写死的,如果我想根据pageNo与pageSize是否为空来判断是否需要分页,该怎么做呢?

如果使用xml来配置的话可以用

<when test='startNo!=null and pageSize != null '>  LIMIT #{startNo},#{pageSize}</when>

如果是用@Select 这种该如何做呢？

方法:用script标签包围，然后像xml语法一样书写

package cn.erongcai.hrplatform.dao.demand;import java.util.List;import org.apache.ibatis.annotations.Mapper;import org.apache.ibatis.annotations.Param;import org.apache.ibatis.annotations.Select;import com.baomidou.mybatisplus.mapper.BaseMapper;import cn.erongcai.hrplatform.model.demand.DemandComment;@Mapperpublic interface DemandCommentMapper extends BaseMapper<DemandComment>{@Select("<script>"+ "SELECT "+ "a.id as 'id',a.create_date as 'createDate',a.content as 'content',"+ "a.parent_id as 'parentId',a.first_comment_id as 'firstCommentId',"+ "b.id as 'fromUser.id',b.realname as 'fromUser.realname',b.avatar as 'fromUser.avatar',"+ "c.id as 'toUser.id',c.realname as 'toUser.realname',c.avatar as 'toUser.avatar' "+ "FROM t_demand_comment a "+ "LEFT JOIN t_user b ON b.id = a.from_uid "+ "LEFT JOIN t_user c ON c.id = a.to_uid "+ "WHERE a.demand_id = #{demandId} "+ "ORDER BY a.create_date ASC "+ "<if test='startNo!=null and pageSize != null '>"+ "LIMIT #{startNo},#{pageSize}"+ "</if>"+ "</script>")public List<DemandComment> listDemandComment(@Param("demandId") Long demandId, @Param("startNo") Integer pageNo, @Param("pageSize") Integer pageSize);}