MyBatis使用分页

分页

思考：为什么要分页？

• 减少数据的处理量

使用Limit分页 

select * from t_user limit 2 offset 1;

使用Mybatis实现分页，核心SQL

1. 接口

       List<User> getUserByLimit(Map<String, Object> map);

2. Mapper.xml

   <?xml version="1.0" encoding="UTF8" ?>
   <!DOCTYPE mapper
           PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
           "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
   
   <mapper namespace="com.shang.dao.UserMapper">
   
       <!--    字段映射    -->
       <resultMap id="UserMapper" type="User">
           <result property="password" column="pwd"/>
       </resultMap>
   
       <select id="getUserByLimit" parameterType="map" resultMap="UserMapper">
           SELECT * FROM t_user limit #{size} OFFSET #{page};
       </select>
   
   
   </mapper>

3. 测试

   @Test
   public void getUserByLimit() {
   
       SqlSession sqlSession = MybatisUtils.getSqlSession();
   
       UserMapper mapper = sqlSession.getMapper(UserMapper.class);
   
       HashMap<String, Object> stringObjectHashMap = new HashMap<>();
   
       stringObjectHashMap.put("size", 2);
       stringObjectHashMap.put("page", 2);
   
       List<User> userByLimit = mapper.getUserByLimit(stringObjectHashMap);
   
       for (User user : userByLimit) {
           System.out.println(user);
       }
   
   }

使用RowBounds分页 

1. 接口

       List<User> getUserByLimit(Map<String, Object> map);

2. Mapper.xml

   <?xml version="1.0" encoding="UTF8" ?>
   <!DOCTYPE mapper
           PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
           "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
   
   <mapper namespace="com.shang.dao.UserMapper">
   
       <!--    字段映射    -->
       <resultMap id="UserMapper" type="User">
           <result property="password" column="pwd"/>
       </resultMap>
   
       <select id="getUserByLimit" parameterType="map" resultMap="UserMapper">
           SELECT * FROM t_user;
       </select>
   
   
   </mapper>

3. 测试

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