MyBatis-07-分页

7、分页

思考：为什么要分页？

• 减少数据的处理量

7.1、使用Limit分页

select * from user limit startIndex,pageSize

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<>();
           map.put("startIndex",0);
           map.put("pageSize",2);
   
           List<User> userList = mapper.getUserByLimit(map);
           for (User user : userList) {
               System.out.println(user);
           }
           sqlSession.close();
       }
   

7.2、RowBounds分页

不再使用SQL实现分页

1. 接口

   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.rui.dao.UserMapper.getUserByRowBounds",null,rowBounds);
   
       for (User user : userList) {
           System.out.println(user);
       }
       sqlSession.close();
   }
   

7.3、分页插件

了解即可，万一以后公司的架构师，说要使用，只需要知道它是什么东西！