MyBatis 注解多对多

喜欢ヅ旅行 2022-05-14 06:58 327阅读 0赞

### 示例：测试多对多关联 ###

**根据数据模型，分别创建t\_user、t\_order、t\_item表。**

![70][]

**然后，输入以下测试数据。**

![70 1][]![70 2][]

![70 3][]

**程序清单：com.po.User.java**

package com.po;
    public class User {
    	private Integer userId;
    	private String userName;
    	private String userSex;
    	private String userAddress;
    	public Integer getUserId() {
    		return userId;
    	}
    	public void setUserId(Integer userId) {
    		this.userId = userId;
    	}
    	public String getUserName() {
    		return userName;
    	}
    	public void setUserName(String userName) {
    		this.userName = userName;
    	}
    	public String getUserSex() {
    		return userSex;
    	}
    	public void setUserSex(String userSex) {
    		this.userSex = userSex;
    	}
    	public String getUserAddress() {
    		return userAddress;
    	}
    	public void setUserAddress(String userAddress) {
    		this.userAddress = userAddress;
    	}
    	@Override
    	public String toString() {
    		return "User [userId=" + userId + ", userName=" + userName + ", userSex=" + userSex + ", userAddress="
    				+ userAddress + "]";
    	}
    }

**程序清单：com.po.Item.java**

package com.po;
    public class Item {
    	private Integer itemId;
    	private String itemName;
    	private double itemPrice;
    	public Integer getItemId() {
    		return itemId;
    	}
    	public void setItemId(Integer itemId) {
    		this.itemId = itemId;
    	}
    	public String getItemName() {
    		return itemName;
    	}
    	public void setItemName(String itemName) {
    		this.itemName = itemName;
    	}
    	public double getItemPrice() {
    		return itemPrice;
    	}
    	public void setItemPrice(double itemPrice) {
    		this.itemPrice = itemPrice;
    	}
    	@Override
    	public String toString() {
    		return "Item [itemId=" + itemId + ", itemName=" + itemName + ", itemPrice=" + itemPrice + "]";
    	}
    }

**程序清单：com.po.Order.java**

package com.po;
    import java.util.List;
    public class Order {
    	private Integer orderId;
    	private User user;
    	private List<Item> items;
    	public Integer getOrderId() {
    		return orderId;
    	}
    	public void setOrderId(Integer orderId) {
    		this.orderId = orderId;
    	}
    	public User getUser() {
    		return user;
    	}
    	public void setUser(User user) {
    		this.user = user;
    	}
    	public List<Item> getItems() {
    		return items;
    	}
    	public void setItems(List<Item> items) {
    		this.items = items;
    	}
    }

**程序清单：com.mapper.UserMapper.java**

package com.mapper;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import com.po.User;
    public interface UserMapper {
    	@Select("select * from t_user where user_id=#{userId}")
    	@Results({@Result(id=true,column="user_id",property="userId"),
    		@Result(column="user_name",property="userName"),
    		@Result(column="user_sex",property="userSex"),
    		@Result(column="user_address",property="userAddress")})
    	User getUserById(Integer userId);
    }

**程序清单：com.mapper.ItemMapper.java**

package com.mapper;
    import java.util.List;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import com.po.Item;
    public interface ItemMapper {
    	@Select("select * from t_item where item_id in(select item_id from t_order where order_id=#{orderId})")
    	@Results({@Result(id=true,column="item_id",property="itemId"),
    			@Result(column="item_name",property="itemName"),
    			@Result(column="item_price",property="itemPrice")})
    	List<Item> getItems(Integer orderId);
    }

**程序清单：com.mapper.OrderMapper.java**

package com.mapper;
    import org.apache.ibatis.annotations.Many;
    import org.apache.ibatis.annotations.One;
    import org.apache.ibatis.annotations.Result;
    import org.apache.ibatis.annotations.Results;
    import org.apache.ibatis.annotations.Select;
    import org.apache.ibatis.mapping.FetchType;
    import com.po.Order;
    public interface OrderMapper {
    	@Select("select * from t_order where order_id=#{orderId}")
    	@Results({@Result(id=true,column="order_id",property="orderId"),
    			@Result(column="user_id",property="user",
    			one=@One(select="com.mapper.UserMapper.getUserById",fetchType=FetchType.EAGER)),
    			@Result(column="item_id",property="items",
    			many=@Many(select="com.mapper.ItemMapper.getItems",fetchType=FetchType.LAZY))})
    	Order getOrderById(Integer orderId);
    }

**程序清单：com.dao.TestDao.java**

package com.dao;
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.List;
    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 com.mapper.OrderMapper;
    import com.po.Item;
    import com.po.Order;
    public class TestDao {
    	private SqlSession	session=null;
    	//获取SqlSession对象
    	public SqlSession getSqlSession() throws IOException {
    		InputStream	is = Resources.getResourceAsStream("mybatis-config.xml");
    		SqlSessionFactory sessionFactory=new SqlSessionFactoryBuilder().build(is);
    		return sessionFactory.openSession();
    	}
    	@Test
    	public void getOrderById() throws IOException {
    		session=getSqlSession();
    		OrderMapper om=session.getMapper(OrderMapper.class);
    		Order order=om.getOrderById(1);
    		System.out.println(order.getUser());
    		List<Item> items=order.getItems();
    		for (Item item : items) {
    			System.out.println(item);
    		}
    	}
    }

**运行TestDao的getOrderById()方法，控制台显示如下：**

![70 4][]

[70]: /images/20220514/a62bd51482b648b5b638d3474468cf1a.png
[70 1]: https://img-blog.csdn.net/20180904154611697?watermark/2/text/aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2R3ZW54dWU=/font/5a6L5L2T/fontsize/400/fill/I0JBQkFCMA==/dissolve/70
[70 2]: /images/20220514/bb6d47476d184c61ae02a7041c7b5653.png
[70 3]: /images/20220514/212d51b866734b91b26a9318b17191bc.png
[70 4]: /images/20220514/006b774288f74a21ba8c33e416e7ed6f.png