分頁

思考：為什麼要分頁？

• 減少資料的處理量

1 使用limit分頁

select * from user limit startIndex,pageSize;

使用Mybatis實現分頁，核心是SQL

1. 介面

List<User> getUserByLimit(HashMap<String,Integer> map);

1. Mapper.XML

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

1. 測試

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

keymap： list.for 可以快速生成增強for迴圈

2 RowBounds分頁

不再使用SQL實現分頁

1. 介面

   List<User> getUserByRowBounds();
   

1. mapper.xml

   <!--分頁-->
   <select id="getUserByRowBounds" resultType="User">
       select * from mybatis.user ;
   </select>
   

2. 測試

   @Test
   public void getUserByRowBounds(){
       SqlSession sqlSession = MybatisUtils.getSqlSession();
       //RowBounds實現
       RowBounds rowBounds = new RowBounds(1, 2);
   
       //通過java程式碼層面實現分頁
       List<User> userList = sqlSession.selectList("com.kuang.dao.UserMapper.getUserByRowBounds",null,rowBounds);
       for (User user : userList) {
           System.out.println(user);
       }
       sqlSession.close();
   }
    
   

3 分頁外掛

Mybatis pageHelper