Mybatis中实现简单查询数据分页功能

Mybatis中实现简单分页

为什么要分页？

• 减少数据的处理量

1.1 使用Limit实现分页

#语法
SELECT * FROM table LIMIT stratIndex，pageSize

SELECT * FROM table LIMIT 5,10; // 检索记录行 6-15  

用mybatis实现分页，核心sql

步骤：

1. mapper接口

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

2. Mapper.xml

   <!--结果集映射-->
   <resultMap id="UserMap" type="User">
       <!--column数据库中的字段，property实体类中的属性-->
       <result column="pwd" property="password"/>
   </resultMap>
      
   <!--分页-->
   <select id="getUserByLimit" resultMap="UserMap" resultType="user">
       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<String, Integer>();
       map.put("startIndex",1);
       map.put("pageSize",2);
   
       List<User> userByLimit = mapper.getUserByLimit(map);
   
       for (User user : userByLimit) {
           System.out.println(user);
       }
   
       sqlSession.close();
   
   }
   

1.2 RowBounds分页

不再使用sql实现分页

步骤：

1. mapper接口

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

2. mapper.xml

   <!--分页-->
   <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(0,3);
   
           //通过java代码层面实现分页
           List<User> userList = sqlSession.selectList("com.ljh.dao.UserMapper.getUserByRowBounds",null,rowBounds);
           for (User user : userList) {
               System.out.println(user);
           }
   
           sqlSession.close();
       }
   

1.3 分页插件（PageHelper）

https://pagehelper.github.io/