Hibernate多对一外键关联(单向)

1.对应关系模型(多个人对应一个地址)

2.pojo类

public class Person {private Long id;private String name;private Address address;//省略get和set}

public class Address {private int id;private String detail;//省略get和set}

3.对应的表结构

mysql> desc person;+-----------+------------+------+-----+---------+----------------+| Field     | Type       | Null | Key | Default | Extra          |+-----------+------------+------+-----+---------+----------------+| personId  | bigint(20) | NO   | PRI | NULL    | auto_increment || addressId | int(11)    | NO   | MUL | NULL    |                |+-----------+------------+------+-----+---------+----------------+

mysql> desc address;+-----------+--------------+------+-----+---------+----------------+| Field     | Type         | Null | Key | Default | Extra          |+-----------+--------------+------+-----+---------+----------------+| addressId | int(11)      | NO   | PRI | NULL    | auto_increment || detail    | varchar(255) | YES  |     | NULL    |                |+-----------+--------------+------+-----+---------+----------------+

4.生成表结构的schema

| person | CREATE TABLE `person` (  `personId` bigint(20) NOT NULL AUTO_INCREMENT,  `addressId` int(11) NOT NULL,  PRIMARY KEY (`personId`),  KEY `FK_qdjkgeoknbp0k9s5r6rds2mj2` (`addressId`),  CONSTRAINT `FK_qdjkgeoknbp0k9s5r6rds2mj2` FOREIGN KEY (`addressId`) REFERENCES `address` (`addressId`)) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=latin1 |

| address | CREATE TABLE `address` (  `addressId` int(11) NOT NULL AUTO_INCREMENT,  `detail` varchar(255) DEFAULT NULL,  PRIMARY KEY (`addressId`)) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=latin1 |

5.配置文件：

单项一对一关联，一个people对应一个address,将address属性加入people

<many-to-one name="address"         column="addressId"        not-null="true"/>

这里用的是many-to-one,多对一，addressId为address的外键。

package org.hibernate.tutorial;import org.hibernate.Session;import org.hibernate.Transaction;import org.hibernate.tutorial.domain.Address;import org.hibernate.tutorial.domain.Person;import org.hibernate.tutorial.util.HibernateUtil;public class uni_many2one_test {public static void main(String[] args) {Session session = HibernateUtil.getSession();Transaction tx = session.getTransaction();tx.begin();Address address = new Address();address.setDetail("hz");Person p1 = new Person();p1.setName("p1");Person p2 = new Person();p2.setName("p2");p1.setAddress(address);p2.setAddress(address);session.save(address);session.save(p1);session.save(p2);session.getTransaction().commit();}}

address应在person之前保存，否则报异常（瞬态实例必须先保存）：

 org.hibernate.TransientPropertyValueException: Not-null property references a transient value - transient instance must be saved before current operation