hibernate一对一关联映射

知识点：

【

第一种：

一对一(Person - IdCard)

1)基于主键的one-to-one(person的映射文件)

<id name=”id”>
<generator class=”foreign”><param name=”property”>idCard</param></generator>
<id>
<one-to-one name=”idCard” constrained=”true”/>

第二种 ：

一对一(Person - IdCard)

2)基于外健的one-to-one，可以描述为多对一，加unique=“true”约束

<one-to-one name=”idCard” property-ref=“person”/>

property-ref用于指定关联类的一个属性，这个属性将会和本外键相对应

<many-to-one name=”person” column=”person_id” unique=”true” not-null=”true”/>

<!-唯一的多对一，其实就便成了一对一了-->

（新建普通java工程） 第一步：配置hibernate环境 、编写hibernate.cfg.xml配置文件

true
com.mysql.jdbc.Driver

jdbc:mysql://localhost:3306/student?useUnicode=true&characterEncoding=UTF-8
com.mysql.jdbc.Driver
root
liyong
org.hibernate.dialect.MySQLDialect

update

第二步：编写实体

IdCard.java Person.java
IdCard.java
public class IdCard {
private int id;
private Date usefulLife;
private Person person;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public Person getPerson() {
return person;
}
public void setPerson(Person person) {
this.person = person;
}
public Date getUsefulLife() {
return usefulLife;
}
public void setUsefulLife(Date usefulLife) {
this.usefulLife = usefulLife;
}
}
Person.java
public class Person {
private int id;
private String name;
private IdCard idCard;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public IdCard getIdCard() {
return idCard;
}
public void setIdCard(IdCard idCard) {
this.idCard = idCard;
}
}

第三步：编写

IdCard.hbm.xml、Person.hbm.xml
IdCard.hbm.xml：
person

-->

第四步：编写测试

public class OneToOneTest {
public static void main(String[] args) {
query(1);
}
@Test
public static void add()
{
Session s = null;
Transaction tx = null;
try {
s = HibernateUtil.getSession();
IdCard idCard = new IdCard();
idCard.setUsefulLife(new Date());
Person p = new Person();
p.setName("p1");
// p.setIdCard(idCard);
idCard.setPerson(p);
tx = s.beginTransaction();
s.save(p);
s.save(idCard);
tx.commit();
} finally {
if (s != null)
s.close();
}
}
@Test
public static void query(int id)
{
Session session = null;
Transaction tx = null;
try {
session = HibernateUtil.getSession();
//Person person=(Person)session.get(Person.class, id);
//System.out.println(person.getIdCard().getUsefulLife());
IdCard idCard=(IdCard)session.get(IdCard.class, id);
System.out.println(idCard.getUsefulLife());
} finally {
if (session != null)
session.close();
}
}
}

第五步：测试