怎么实现MyBatis limit分页设置？

2021-07-14 16:42:16 浏览数 (21)

本文将为您介绍MyBatis limit一种错误的写法和两种正确的写法，其中一种正确写法还需要在Java语言中额外设置get函数。

错误的写法：

<select id="queryMyApplicationRecord" parameterType="MyApplicationRequest" resultMap="myApplicationMap">
 SELECT
 a.*,
 FROM
 tb_user a
 WHERE 1=1
 <if test="ids != null and ids.size()!=0">
  AND a.id IN
  <foreach collection="ids" item="id" index="index"
     open="(" close=")" separator=",">
   #{id}
  </foreach>
 </if>
 <if test="statusList != null and statusList.size()!=0">
  AND a.status IN
  <foreach collection="statusList" item="status" index="index"
     open="(" close=")" separator=",">
   #{status}
  </foreach>
 </if>
 ORDER BY a.create_time desc
 LIMIT (#{pageNo}-1)*#{pageSize},#{pageSize}; // 错误
</select>

 在MyBatis中LIMIT之后的语句不允许的变量不允许进行算数运算，会报错。

 正确的写法一：

<select id="queryMyApplicationRecord" parameterType="MyApplicationRequest" resultMap="myApplicationMap">
 SELECT
 a.*,
 FROM
 tb_user a
 WHERE 1=1
 <if test="ids != null and ids.size()!=0">
  AND a.id IN
  <foreach collection="ids" item="id" index="index"
     open="(" close=")" separator=",">
   #{id}
  </foreach>
 </if>
 <if test="statusList != null and statusList.size()!=0">
  AND a.status IN
  <foreach collection="statusList" item="status" index="index"
     open="(" close=")" separator=",">
   #{status}
  </foreach>
 </if>
 ORDER BY a.create_time desc
 LIMIT ${(pageNo-1)*pageSize},${pageSize}; （正确）
</select>

 正确的写法二：（推荐）

<select id="queryMyApplicationRecord" parameterType="MyApplicationRequest" resultMap="myApplicationMap">
 SELECT
 a.*,
 FROM
 tb_user a
 WHERE 1=1
 <if test="ids != null and ids.size()!=0">
  AND a.id IN
  <foreach collection="ids" item="id" index="index"
     open="(" close=")" separator=",">
   #{id}
  </foreach>
 </if>
 <if test="statusList != null and statusList.size()!=0">
  AND a.status IN
  <foreach collection="statusList" item="status" index="index"
     open="(" close=")" separator=",">
   #{status}
  </foreach>
 </if>
 ORDER BY a.create_time desc
 LIMIT #{offSet},#{limit}; （推荐，代码层可控）
</select>

 分析：方法二的写法，需要再请求参数中额外设置两个get函数，如下：

@Data
public class QueryParameterVO {
 
 private List<String> ids;
 
 private List<Integer> statusList;
 
 // 前端传入的页码
 private int pageNo; // 从1开始
 
 // 每页的条数
 private int pageSize;
 
 // 数据库的偏移
 private int offSet;
 
 // 数据库的大小限制
 private int limit;
 
 // 这里重写offSet和limit的get方法
 public int getOffSet() {
  return (pageNo-1)*pageSize;
 }
 
 public int getLimit() {
  return pageSize;
 }
}

到此这篇关于MyBatis limit分页设置的错误写法和两种正确实现写法以及第二种正确写法关联get函数的文章内容到此结束了,更多相关MyBatis limit分页内容请搜索W3Cschool以前的文章或继续浏览下面的相关文章希望大家以后多多支持W3Cschool！


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