mybatis-plus入门demo

mybatis-plus入门demo

      com.baomidou
      mybatis-plus
      3.3.2

• 普通项目：

  • 创建SqlSessionFactoryBuilder时使用Mybatis_plus的 MybatisSqlSessionFactoryBuilder

  • 对实体类使用注解

    @Getter
    @Setter
    @NoArgsConstructor
    @AllArgsConstructor
    @TableName("user")
    public class User{
        private int id;
        private String name;
        private String age;
        private String email;
    }
    //使用lombok注解快速生成方法
    //使用Mybatis-plus的TableName注解配置：数据库表和实体类的映射，即该实体类对应的哪一个数据库表
    

  • 创建接口Mapper，继承baseMapper

    import com.baomidou.mybatisplus.core.mapper.baseMapper;
    import com.xyd.bean.User;
    
    import java.util.List;
    
    public interface UserMapper extends baseMapper {
    //创建接口继承baseMapper
        List all();
        //该方法用于查询，与mybatis—plus的查询相比较
    }
    

    
        
        
            select * from user
        
    
    

  • 创建SqlSessionFactoryUtil

    public class SqlSessionFactoryUtil {
        private SqlSession sqlSession = null;
        private static SqlSessionFactory factory = null;
        private static String ADDRESS_CORE = "Mybatis_core.xml";
    
        static {
            try {
                init();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    
        public static void init() throws IOException {
            Reader reader = Resources.getResourceAsReader(ADDRESS_CORE);
            MybatisSqlSessionFactoryBuilder builder = new MybatisSqlSessionFactoryBuilder();
            factory = builder.build(reader);
            reader.close();
        }
    
        public static SqlSession  getSqlSession() {
            return factory.openSession(true);
        }
    }
    

  • 创建测试类

    public class MpTest {
        private UserMapper userMapper;
        private SqlSession sqlSession = null;
    
        @Before
        public void init() {
            sqlSession = SqlSessionFactoryUtil.getSqlSession();
            userMapper = sqlSession.getMapper(UserMapper.class);
        }
    
        @Test
        public void Demo1() {
            List users = userMapper.selectList(null);
            assert users.size()>0;
            System.out.println("sss");
        }
        
        @Test
        public void Demo2() {
            List list = userMapper.all();
            System.out.println(list.size());
        }
    
    }
    

  • 分别运行两个demo

    • 从日志中可以看到两个demo的运行语句不一样，但是demo1我们没有写过语句

    • Demo1的运行sql语句是

      SELECT id,name,age,email FROM user 
      

    • Demo2的运行sql语句是

      select * from user
      

    • 所以demo1简化了我们的工作，一些简单的sql语句mybatis-plus自动就可以帮我们实现.js/