[5] Mybatis realizes paging [limit] [RowBounds]

7, paging

Why paging?

• Reduce the amount of data processing

7.1, use limit paging

grammar:

select * from users limit startIndex,pageSize;
select * from users limit 3;

Use Mybatis to achieve paging, core SQL

1. interface

   List<User> getUserLimit(Map<String,Integer> map);
   

2. mapper.xml

       <select id="getUserLimit" parameterType="map" resultMap="UserMap">
           select * from users limit #{startIndex},#{pageSize}
       </select>
   

3. junit unit test

       @Test
       public void getUserLimit(){
         
         
           SqlSession sqlSession;
           try {
         
         
               sqlSession = MybatisUtils.getSqlSession();
               UserMapper mapper = sqlSession.getMapper(UserMapper.class);
               HashMap<String,Integer> map = new HashMap<String,Integer>();
               map.put("startIndex",2);
               map.put("pageSize",2);
               List<User> users = mapper.getUserLimit(map);
               for (User user : users) {
         
         
                   System.out.println(user);
               }
           }finally {
         
         
               MybatisUtils.closeSqlSession();
           }
   
       }
   

7.2, RowBounds paging

No longer use SQL to implement paging

1. interface

   	List<User> getUserByRowBounds();
   

2. mapper.xml

       <select id="getUserByRowBounds" resultMap="UserMap">
           select * from users
       </select>
   

3. junit unit test

       @Test
       public void getUserByRowBounds(){
         
         
           SqlSession sqlSession = MybatisUtils.getSqlSession();
           RowBounds rowBounds = new RowBounds(1,2);
   
           List<User> users = sqlSession.selectList("com.kuber.dao.UserMapper.getUserByRowBounds", null, rowBounds);
           for (User user : users) {
         
         
               System.out.println(user);
           }
           sqlSession.close();
       }
   

7.3, paging plugin

Understand, you can refer to the document to use, if you use it later, you know what it is