mybatis_7分頁查詢

思考：爲何要分頁？

• 減小數據的處理量

7.一、使用Limit分頁

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

使用Mybatis實現分頁，核心SQL

1. 接口

   //分頁
   List<User> getUserByLimit(Map<String,Integer> map);

2. Mapper.xml

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

3. 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",1);
       map.put("pageSize",2);
   
       List<User> userList =  mapper.getUserByLimit(map);
       for (User user : userList) {
       System.out.println(user);
       }
   
       sqlSession.close();
       }

7.二、RowBounds分頁

再也不使用SQL實現分頁，使用java代碼實現分頁，不推薦使用

1. 接口

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

2. mapper.xml

   <!--分頁2-->
   <select id="getUserByRowBounds" resultMap="UserMap">
       select * from  mybatis.user
   </select>

3. 測試

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

7.三、分頁插件

mybaits-pagehelper