文章目录

• 分页
• 1. 使用Limit分页
• 2. 使用RowBounds分页
• 3. 插件实现

分页

为什么要用分页？

• 较少数据的处理量

1. 使用Limit分页

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

编写接口UserMapper.java：

// 分页1
List<User> getUserByLimit(Map<String,Integer> map);

修改UserMapper.xml

<!-- 这里还是使用了ResultMap结果集映射 -->
<resultMap id="userMap" type="user">
        <result column="id" property="id"/>
        <result column="name" property="name"/>
        <result column="pwd" property="password"/>
    </resultMap>
<select id="getUserByLimit" resultMap="userMap" resultType="user">
    select * from user limit #{startIndex},#{pageSize};
</select>

编写测试方法：

public class UserDaoTest {
    static Logger logger = Logger.getLogger(UserDaoTest.class);
    @Test
    public void getUserByLimit(){
        logger.debug("进入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> userByLimit = mapper.getUserByLimit(map);
        for (User user : userByLimit) {
            logger.info(user);
        }
        sqlSession.close();
    }
}

2. 使用RowBounds分页

编写接口UserMapper.java：

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

修改UserMapper.xml

<resultMap id="userMap" type="user">
    <result column="id" property="id"/>
    <result column="name" property="name"/>
    <result column="pwd" property="password"/>
</resultMap>
<select id="getUserByRowBounds" resultMap="userMap" resultType="user">
    select * from user;
</select>

编写测试方法：

public class UserDaoTest {
    static Logger logger = Logger.getLogger(UserDaoTest.class);
    @Test
    public void getUserByRowBounds(){
        logger.debug("getUserByRowBounds");
        SqlSession sqlSession = MyBatisUtils.getSqlSession();
        // 使用RowBounds实现分页
        RowBounds rowBounds = new RowBounds(0, 2);
        List<User> userList = sqlSession.selectList("com.xxc.dao.UserMapper.getUserByRowBounds",null,rowBounds);
        for (User user : userList) {
            logger.debug(user);
        }
        sqlSession.close();
    }
}

3. 插件实现

PageHelper文档：

https://pagehelper.github.io/docs/howtouse/

了解即可。