hibernate中的关系映射01一对多映射

要了解的概念：

关系

一对多

多对一

多对多

一对一

单项关联

双向关联

级联操作

需求：客户与订单的关系是一对多

准备项目2

（1）创建项目

hibernate02relation

（2）引入jar，同前一个项目

（3）复制实体、映射、配置、工具类

1、订单表（也可以后面自动创建）

Create Table

CREATE TABLE `t_order` (
`id` bigint(20) NOT NULL AUTO_INCREMENT,
`order_no` varchar(20) DEFAULT NULL,
`product_name` varchar(100) DEFAULT NULL,
`customer_id` bigint(20) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `FKesy3n2gc3fa0s3trrk3tvyv9a` (`customer_id`),
CONSTRAINT `FKesy3n2gc3fa0s3trrk3tvyv9a` FOREIGN KEY (`customer_id`) REFERENCES `t_customer` (`c_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8mb4;

2、创建Order实体类

package name.yaohuan.hibernate.pojo.one2many;

/**

* 订单（多方）

public class Order {

private Long id;

private String orderNo;

private String productName;

//关联客户

private Customer customer;
}

3、修改Customer实体类

package name.yaohuan.hibernate.pojo.one2many;

import java.io.Serializable;

import java.util.HashSet;

import java.util.Set;

/**

* 客户（一方）

public class Customer{

private Long id;

private String name;

private Character gender;

private Integer age;

private String level;

//关联订单

private Set<Order> orders = new HashSet<Order>();
}

4、在Customer配置文件中配置一对多

<class name="Customer" table="t_customer">

......

<one-to-many class="Order"/>

</set>

</class>

5、Order配置文件

<hibernate-mapping package="com.**.hibernate.pojo.one2many">

<class name="Order" table="t_order">

<id name="id" column="id">

</id>

<many-to-one name="customer" class="Customer" column="customer_id" />

</class>

</hibernate-mapping>

6、将映射文件加入hibernte.cfg.xml

<mapping resource="com/**/hibernate/pojo/one2many/Customer.hbm.xml"/>

<mapping resource="com/**/hibernate/pojo/one2many/Order.hbm.xml"/>

7、测试新增关联数据

public class One2manyTest {

    /**
     * 需求：1个客户 2张订单
     */
    @Test
    public void testCreateOrder(){

        //准备数据
        Customer customer = new Customer();
        customer.setName("老王");
        customer.setGender('男');
        customer.setAge(18);
        customer.setLevel("VIP");

        Order o1 = new Order();
        o1.setOrderNo("210009070001");
        o1.setProductName("看透SpringMVC源代码分析与实践");

        Order o2 = new Order();
        o2.setOrderNo("210009070002");
        o2.setProductName("淘宝技术这十年");

        Session session = HibernateUtil.openSession();
        Transaction tx = session.beginTransaction();

        //建立一对多双向关系(非必须，也可以建立单项关联)
        customer.getOrders().add(o1);
        customer.getOrders().add(o2);

        o1.setCustomer(customer);
        o2.setCustomer(customer);

        //保存数据
        session.save(customer);
        session.save(o1);
        session.save(o2);

        //数据提交
        tx.commit();
        session.close();
    }
}

8、测试查询订单

/**

 * 查询操作
 */
@Test
public void testSearch(){

    Session session = HibernateUtil.openSession();
    Transaction tx = session.beginTransaction();

    //查询一个客户，关联查询订单
    Customer customer = session.get(Customer.class, 1L);
    System.out.println(customer.getName()+"的订单：");
    Set<Order> orders = customer.getOrders();
    for (Order order : orders) {
        System.out.println(order.getOrderNo()+","+order.getProductName());
    }

    tx.commit();
    session.close();
}

hibernate中的关系映射01一对多映射

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