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How to use Mybatis to implement paging query in Java

王林
王林forward
2023-05-07 23:19:061022browse

1.map collection

Our paging requires multiple parameters, not just one parameter. When we need to receive multiple parameters, we use a Map collection to load them.

public List<Student>  pagination(int start ,int end) throws Exception {
        //得到连接对象
        SqlSession sqlSession = MybatisUtil.getSqlSession();
        try{
            //映射文件的命名空间.SQL片段的ID,就可以调用对应的映射文件中的SQL
 
 
            /**
             * 由于我们的参数超过了两个,而方法中只有一个Object参数收集
             * 因此我们使用Map集合来装载我们的参数
             */
            Map<String, Object> map = new HashMap();
            map.put("start", start);
            map.put("end", end);
            return sqlSession.selectList("StudentID.pagination", map);
        }catch(Exception e){
            e.printStackTrace();
            sqlSession.rollback();
            throw e;
        }finally{
            MybatisUtil.closeSqlSession();
        }
    }
    public static void main(String[] args) throws Exception {
        StudentDao studentDao = new StudentDao();
        List<Student> students = studentDao.pagination(0, 3);
        for (Student student : students) {
 
            System.out.println(student.getId());
 
        }
 
}

2. LIMIT keyword

(1) mapper code: use the limit keyword to implement paging

    <select id="selectByPageInfo" resultMap="BaseResult">
        select * from tb_user limit #{pageNo}, #{pageSize}
    </select>

(2) Business The layer directly calls

    public List<User> findByPageInfo(PageInfo info) {
        return userMapper.selectByPageInfo(info);
    }

(3) The control layer directly calls

We all know that the mybatis framework is better for data applications. In terms of data search, we sometimes involve the operation of paging search. I believe this is also a knowledge point that many people urgently need to learn.

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