MyBatis Limit and RowBounds realize paging

---

〇、Preparation

database:

create database MyBatis_DB;
use MyBatis_DB;
create table user(
	id int primary key auto_increment,
	name varchar(32) not null,
	pwd varchar(32) not null
);

Then just insert a few pieces of data

Next, create a Mavenproject, injection MySql, MyBatis, Junit, LOG4Jdependence

Create a table Userentity class, create an UserMapperinterface, UserMapper.xmland test class

Next, start to implement paging query

One, Limit realizes paging

The first step is to write the UserMapperinterface

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

The second step is to write a UserMapper.xmlfile and write sql, where the receiving parameter is one Map:

    <select id="findUserByLimit" resultType="User" parameterType="map">
        select * from mybatis_db.user limit #{startPage},#{Page}
    </select>

The third step is to write a test class. First, make a Mapstorage parameter to be transmitted, then call the method, output the result, and finally close the connection

    //获取SqlSession
    private SqlSession sqlSession = MyBatisUtils.getSqlSession();
    //获取mapper
    private UserMapper mapper = sqlSession.getMapper(UserMapper.class);   
    //limit分页
    @Test
    public void findUserByLimitTest(){
    
    
        Map<String,Integer> map = new HashMap<String, Integer>();
        map.put("startPage",0);
        map.put("Page",5);
        List<User> userByLimit = mapper.findUserByLimit(map);
        for (User user : userByLimit) {
    
    
            System.out.println(user);
        }
        sqlSession.close();
    }

Output result:

Two, RowBounds realizes paging | not recommended

The first step is to write the interface

List<User> findUserByRowBounds();

The second step, writing XML:

    <select id="findUserByRowBounds" resultType="User">
        select * from mybatis_db.user;
    </select>

The third step is to write the test class

    //获取SqlSession
    private SqlSession sqlSession = MyBatisUtils.getSqlSession();
    //RowBounds实现分页
    @Test
    public void findUserByRowBoundsTest(){
    
    
        //RowBounds实现
        RowBounds rowBounds = new RowBounds(0, 5);
        List<User> UserList = sqlSession.selectList(
                "com.wzq.mapper.UserMapper.findUserByRowBounds",
                null, rowBounds);
        for (User user : UserList) {
    
    
            System.out.println(user);
        }
        sqlSession.close();
    }

test: