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最近无心上班，不知道咋回事

基本要点

1、limit分页

核心是sql中使用limit关键字，第一个参数代表起始下标，下标从0开始，第二个参数代表查询长度

select * from table limit startIndex,pageSize;

select * from table limit 3;  //代表【0，3】

我们写个测试代码试一下
首先我们先在接口类中新增一个分页查询的方法，我们把起始下标和要查的条数塞进map集合

package com.decade.mapper;

import com.decade.entity.User2;
import java.util.Map;

public interface UserMapper {
    List<User2> getUserInfoLimit(Map<String, Integer> map);
}

接着我们在SQL映射文件中编写对应的SQL

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.decade.mapper.UserMapper">

    <resultMap id="userInfo" type="com.decade.entity.User2">
        <result property="userId" column="id" jdbcType="VARCHAR"/>
        <result property="name" column="name" jdbcType="VARCHAR"/>
        <result property="sex" column="sex" jdbcType="VARCHAR"/>
        <result property="age" column="age" jdbcType="INTEGER"/>
    </resultMap>

    <select id="getUserInfoLimit" parameterType="map" resultMap="userInfo">
        select id,name,sex,age from t_decade_user limit #{startIndex}, #{pageSize};
    </select>
</mapper>

最后我们写个测试方法测一下

import com.decade.entity.User2;
import com.decade.mapper.UserMapper;
import com.decade.utils.MybatisUtils;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class UserDaoTest {

    @Test
    public void test3() {
        // 第一步：获取sqlSession对象
        SqlSession sqlSession = MybatisUtils.getSqlSession();

        try {
            UserMapper userDao = sqlSession.getMapper(UserMapper.class);

            Map<String, Integer> map = new HashMap<>();
            map.put("startIndex", 0);
            map.put("pageSize", 2);
            List<User2> userList = userDao.getUserInfoLimit(map);

            // 循环输出查询到的user信息
            userList.forEach(System.out::println);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 关闭sqlSession
            sqlSession.close();
        }
    }
}