关于mybatis:Mybatis分页查询

​
思考：为什么要分页?
缩小数据的处理量
1、应用 Limit 分页
语法:

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

应用 Mybatis 实现分页，外围 SQL
接口

  /**
  * 分页查问
  * @return
  */
  List<User> getUserByLimt(Map<String,Integer> map);

Mapper.xml
<!– 分页实现查问 –>
<select id=”getUserByLimt” parameterType=”map” resultMap=”UserMap”>
select * from mybatis.user limit #{startIndex},#{pageSize}
</select>

    // 测试
    public void getUserByLimt(){SqlSession sqlsession = MybatisUtil.getSqlsession();
        UserMapper mapper = sqlsession.getMapper(UserMapper.class);
        HashMap<String, Integer> map = new HashMap<String, Integer>();
        map.put("startIndex",0);
        map.put("pageSize",3);
        List<User> userByLimt = mapper.getUserByLimt(map);
        for (User user : userByLimt) {System.out.println(user);
        }
    }

2、RowBounds 分页
不在应用 SQL 实现分页

接口

 /**
 *
 * @return
 */
 List<User> getUserByRowBounds();

Mapper.xml

<!– 分页实现查问 –>

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

  // 测试
public void getUserByRowBounds(){SqlSession sqlsession = MybatisUtil.getSqlsession();
    //RowBounds 实现
   RowBounds rowBounds = new RowBounds(1, 2);
   // 通过 java 层面实现分页
   List<User> list = sqlsession.selectList("com.aostarit.dao.UserMapper.getUserByRowBounds",null,rowBounds);
   for (User user : list) {System.out.println(user);
    }
   // 敞开 sqlSession
   sqlsession.close();}