分页的两种用法以及插件问题

思考：什么是分页？

• 减少数据的处理量

1.使用Limit分页

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

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  mybatis.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<String, Integer>();
    map.put("startIndex",1);
    map.put("pageSize",2);

    List<User> userList =  mapper.getUserByLimit(map);
    for (User user : userList) {
    System.out.println(user);
    }

    sqlSession.close();
    }

2.RowBounds分页

不再使用SQL实现分页

1. 接口

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

2. mapper.xml

<!--分页2-->
<select id="getUserByRowBounds" resultMap="UserMap">
    select * from  mybatis.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.kuang.dao.UserMapper.getUserByRowBounds",null,rowBounds);

    for (User user : userList) {
    System.out.println(user);
    }

    sqlSession.close();
    }

3.分页插件

了解即可，万一以后公司的构架师说要使用，你需要知道它是什么东西！