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;
}
}
|
|
