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Mybatis+MP实现

夕颜合欢落 2022-04-14 阅读 76
springjava

第一步,将UserMapper继承BaseMapper,将拥有了BaseMapper中的所有方法:

package cn.itcast.mapper;

import cn.itcast.pojo.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;

import java.util.List;

public interface UserMapper extends BaseMapper<User> {
    List<User> findAll();
}

第二步,使用MP中的MybatisSqlSessionFactoryBuilder进程构建:

package cn.itcast;

import cn.itcast.mapper.UserMapper;
import cn.itcast.pojo.User;
import com.baomidou.mybatisplus.core.MybatisSqlSessionFactoryBuilder;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class TestMybatisPlus {
    @Test
    public void test1() throws IOException {
        InputStream resourceAsStream = Resources.getResourceAsStream("mybatis-config.xml");
        SqlSessionFactory sqlSessionFactory = new MybatisSqlSessionFactoryBuilder().build(resourceAsStream);
        SqlSession sqlSession = sqlSessionFactory.openSession();
        UserMapper mapper = sqlSession.getMapper(UserMapper.class);
        List<User> users = mapper.selectList(null);
        for (User user : users) {
            System.out.println(user);
        }
    }
}

运行报错:

 原因:mp数据库下不存在user表

解决方法:在user实体中添加TableName("tb_user"),指定数据库表名

 

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