【Mybatis】使用Mybatis的原始Dao层进行数据库的连接

1、原始Dao开发方法需要程序员编写Dao接口和Dao实现类。

2、编写映射文件

	
		select * from user where id = #{id}
	

	
	
		select LAST_INSERT_ID() 
	
	  insert into user(username,birthday,sex,address) 
	  values(#{username},#{birthday},#{sex},#{address})
	

3、Dao层接口

Public interface UserDao {
	public User getUserById(int id) throws Exception;
	public void insertUser(User user) throws Exception;
}

4、Dao实现类

Public class UserDaoImpl implements UserDao {
	
	//通过构造方法的方式注入SqlSessionFactory
	public UserDaoImpl(SqlSessionFactory sqlSessionFactory){
		this.setSqlSessionFactory=sqlSessionFactory;
	}
	
	private SqlSessionFactory sqlSessionFactory;
	@Override
	public User getUserById(int id) throws Exception {
		SqlSession session = sqlSessionFactory.openSession();
		User user = null;
		try {
			//通过sqlsession调用selectOne方法获取一条结果集
			//参数1：指定定义的statement的id,参数2：指定向statement中传递的参数
			user = session.selectOne("test.findUserById", 1);
			System.out.println(user);
						
		} finally{
			session.close();
		}
		return user;
	}
	
	@Override
	Public void insertUser(User user) throws Exception {
		SqlSession sqlSession = sqlSessionFactory.openSession();
		try {
			sqlSession.insert("insertUser", user);
			sqlSession.commit();
		} finally{
			session.close();
		}
		
	}
}

5、测试

private SqlSessionFactory sqlSessionFactory;
	
	@Before
	public void init() throws Exception {
		SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder();
		InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml");
		sqlSessionFactory = sessionFactoryBuilder.build(inputStream);
	}

	@Test
	public void testGetUserById() {
		UserDao userDao = new UserDaoImpl(sqlSessionFactory);
		User user = userDao.getUserById(22);
		System.out.println(user);
	}
}

6、存在的问题

原始Dao开发中存在以下问题：
 Dao方法体存在重复代码：通过SqlSessionFactory创建SqlSession，调用SqlSession的数据库操作方法
 调用sqlSession的数据库操作方法需要指定statement的id，这里存在硬编码，不利于开发维护。