分页

为什么要分页?

减少数据的处理量

语法:

1	select * from user limit startIndex, pageSize;

使用SQL语句实现分页:

接口

1 2	// 分页查询 List<User> getUserByLimit(Map<String, Integer> map);

Mapper.xml

1
2
3

<select id="getUserByLimit" parameterType="map" resultMap="UserMap">
    select * from mybatis.user limit #{startIndex}, #{pageSize};
</select>

测试

@Test
public void getUserByLimitTest(){
    SqlSession sqlSession = MybtisUtils.getSqlSession();
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);

    Map<String, Integer> map = new HashMap<>();
    map.put("startIndex", 1);
    map.put("pageSize", 2);

    List<User> users = mapper.getUserByLimit(map);

    for (User user : users) {
        System.out.println(user);
    }

    sqlSession.close();
}

输出为:

[org.apache.ibatis.transaction.jdbc.JdbcTransaction]-Opening JDBC Connection
[org.apache.ibatis.datasource.pooled.PooledDataSource]-Created connection 1631086936.
[org.apache.ibatis.transaction.jdbc.JdbcTransaction]-Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@61386958]
[com.lxb.dao.UserMapper.getUserByLimit]-==>  Preparing: select * from mybatis.user limit ?, ?; 
[com.lxb.dao.UserMapper.getUserByLimit]-==> Parameters: 1(Integer), 2(Integer)
[com.lxb.dao.UserMapper.getUserByLimit]-<==      Total: 2
User{id=2, name='John', password='123456'}
User{id=3, name='Jay', password='123456'}
[org.apache.ibatis.transaction.jdbc.JdbcTransaction]-Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@61386958]
[org.apache.ibatis.transaction.jdbc.JdbcTransaction]-Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@61386958]
[org.apache.ibatis.datasource.pooled.PooledDataSource]-Returned connection 1631086936 to pool.

RowBounds分页

不推荐, 在Mapper.xml中查询整个表单, 然后测试时摘取, 不高效

分页插件

MyBatis分页插件 PageHelper