用mabatis设计一个商品订单管理系统

首先，我们需要在MyBatis中配置数据源和Mapper映射文件。假设我们有两个表，一个是商品表（product），另一个是订单表（order），表结构如下：

- product表：id, name, price, stock
- order表：id, user_id, product_id, quantity, total_price, create_time

在MyBatis配置文件中，我们需要配置数据源和Mapper映射文件，示例代码如下：

<configuration>
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC"/>
      <dataSource type="POOLED">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/mydatabase"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
      </dataSource>
    </environment>
  </environments>
  <mappers>
    <mapper resource="com/example/mapper/ProductMapper.xml"/>
    <mapper resource="com/example/mapper/OrderMapper.xml"/>
  </mappers>
</configuration>

然后，我们需要编写Mapper映射文件，分别对应商品表和订单表的操作。示例代码如下：

ProductMapper.xml:

<mapper namespace="com.example.mapper.ProductMapper">
  <select id="selectById" resultType="com.example.model.Product">
    select id, name, price, stock from product where id = #{id}
  </select>
  <update id="updateStock" parameterType="com.example.model.Product">
    update product set stock = #{stock} where id = #{id}
  </update>
</mapper>

OrderMapper.xml:

<mapper namespace="com.example.mapper.OrderMapper">
  <insert id="insertOrder" parameterType="com.example.model.Order">
    insert into order (user_id, product_id, quantity, total_price, create_time)
    values (#{userId}, #{productId}, #{quantity}, #{totalPrice}, #{createTime})
  </insert>
  <select id="selectByUserId" resultType="com.example.model.Order">
    select id, user_id as userId, product_id as productId, quantity, total_price as totalPrice, create_time as createTime
    from order
    where user_id = #{userId}
  </select>
</mapper>

最后，我们可以在Java代码中使用MyBatis提供的SqlSession类来执行上述操作，示例代码如下：

public class OrderService {
  private SqlSessionFactory sqlSessionFactory;

  public OrderService(SqlSessionFactory sqlSessionFactory) {
    this.sqlSessionFactory = sqlSessionFactory;
  }

  public Product getProductById(int id) {
    try (SqlSession session = sqlSessionFactory.openSession()) {
      ProductMapper mapper = session.getMapper(ProductMapper.class);
      return mapper.selectById(id);
    }
  }

  public void updateProductStock(Product product) {
    try (SqlSession session = sqlSessionFactory.openSession()) {
      ProductMapper mapper = session.getMapper(ProductMapper.class);
      mapper.updateStock(product);
      session.commit();
    }
  }

  public void insertOrder(Order order) {
    try (SqlSession session = sqlSessionFactory.openSession()) {
      OrderMapper mapper = session.getMapper(OrderMapper.class);
      mapper.insertOrder(order);
      session.commit();
    }
  }

  public List<Order> getOrderByUserId(int userId) {
    try (SqlSession session = sqlSessionFactory.openSession()) {
      OrderMapper mapper = session.getMapper(OrderMapper.class);
      return mapper.selectByUserId(userId);
    }
  }
}

以上就是使用MyBatis设计商品订单管理系统的基本流程。当然，实际情况可能更加复杂，需要根据具体业务需求进行定制化开发。