MyBatis（五）：分页

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Limit实现分页

• 提醒：不要忘了应该把SqlSession对象放在finily要关闭！本文为了方便省去这步！

• 实体类

package com.rzp.pojo;
​
public class User {
    private int id;
    private String name;
    private String pwd;
 //有参+无参构造+get+set+toString
}
​

• Mapper.xml

   <select id="getUserByLimit" parameterType="map" resultType="user">
        select * from mybatis.user limit #{startIndex},#{pageSize}
    </select>

• Mapper接口

public interface UserMapper {
    //分页
    List<User> getUserByLimit(Map<String,Integer> map);
}

• 测试方法

   @Test
    public void getUserByLimit(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        //使用map传参数，通过sql的limit条件实现分页
        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.toString());
        }
        sqlSession.close();
    }

RowBounds

• 好处：符合面向对象的规范

• 坏处：先查询了所有，占用资源太多；使用的sqlSession.selectList的方法，该方法比较旧，官方不推荐使用。

• Mapper.xml

   <select id="getUserByRowBounds" resultType="user">
        select * from mybatis.user
    </select>

• Mapper接口

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

• 测试方法

   @Test //RowBounds分页
    public void getUserByRowBounds(){
        SqlSession sqlSession = MybatisUtils.getSqlSession();
        //RowBounds实现
        RowBounds rowBounds = new RowBounds(0, 2);
        //传入rowBounds
        List<User> userList = sqlSession.selectList("com.rzp.dao.UserMapper.getUserByRowBounds",null,rowBounds);
        for (User o : userList) {
            System.out.println(o.toString());
        }
        sqlSession.close();
    }