mybatis学习（六、分页）

六、分页

为什么要分页？

• 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 0,2;	从第0行开始查2个

使用mybatis实现分页，核心就是sql

1. 接口

   //分页查询
   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 testGetUserLimit(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
       Map<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();
   }
   

2.RowBounds分页

不再使用SQL实现分页

1. 接口

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

2. Mapper.xml

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

3. 测试

   @Test
   public void testGetUserByRowBounds(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       //RowBounds实现
       RowBounds rowBounds = new RowBounds(0, 2);
   
       //通过java代码层面实现分页
       List<User> userList = sqlSession.selectList("com.lzt.dao.UserMapper.getUserByRowBounds",null,rowBounds);
   
   
       sqlSession.close();
   }
   

3.分页插件

MyBatis 分页插件 PageHelper

https://pagehelper.github.io/

大型复杂项目中使用，具体进官方文档中查看，有详细使用教程