Mybatis学习分页

为什么要分页

• 减少数据的使用量

使用Limit分页

语法：select * from user limit startIndex,pageSize;
select * from user limit 3;   #[0,3]

使用Mybatis实现分页，核心SQL

1. 接口

 // 分页
 List<User> getUserByLimit(Map<String,Integer> map);

2. Mapper.xml

<!--分页-->
<select id="getUserByLimit" parameterType="map" resultMap="UserMap">
    select * from user limit #{startIndex},#{pageSize}
</select> 

3. 测试

@Test
public void getUserByLimit(){
    SqlSession sqlSession = MybatisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
    HashMap<String, Integer> map = new HashMap<>();
    map.put("startIndex",0);
    map.put("pageSize",2);
    List<User> userList = mapper.getUserByLimit(map);
    for (User user: userList){
        System.out.println(user);
    }
    sqlSession.close();
}

RowBounds分页

不在使用SQL实现分页

1. 接口

// 分页2
List<User> getUserByRowBounds();

2. mapper.xml

<select id="getUserByRowBounds" resultMap="UserMap">
    select * from user
</select>

3. 测试

@Test
public void getUserByRowBounds() {
    SqlSession sqlSession = MybatisUtils.getSqlSession();

    //RowBounds实现
    RowBounds rowBounds = new RowBounds(1,2);
    //通过java代码层面实现分页
    List<User> userList = sqlSession.selectList("com.lyh.dao.UserMapper.getUserByRowBounds",null,rowBounds);
    for (User user: userList){
        System.out.println(user);
    }
    sqlSession.close();
}

分页插件

Mybatis PageHelper官方文档：https://pagehelper.github.io/docs/