Hibernate一对一关联映射

1.一对一的主键单向关联

(a)Card.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.yyming.hibernate.Card">
		<id name="id">
			<generator class="native" />
		</id>
		<property name="idCard" />
	</class>
</hibernate-mapping>

 (b)Person.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
      <class name="com.yyming.hibernate.Person">
	<id name="id">
		<generator class="foreign" >
			  <!-- person中的id来源于card，即共享card中的主键 -->
			   <param name="property">card</param>
		</generator>
	</id>
	<property name="name" />
	<!-- constrained="true",当前主键上存在一个约束，表明person表中的主键作为外键参照了card表 -->
	<one-to-one name="card" constrained="true"/>
       </class>
</hibernate-mapping>

 (c)Person.java和Card.java

public class Person {
	private int  id;
	private String name;
	private Card card;
	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 Card getCard() {
		return card;
	}
	public void setCard(Card card) {
		this.card = card;
	}
}

 

public class Card {
	private int id;
	private String idCard;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getIdCard() {
		return idCard;
	}
	public void setIdCard(String idCard) {
		this.idCard = idCard;
	}
}

 2.一对一的主键双向关联

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.yyming.hibernate.Card">
		<id name="id">
			<generator class="native" />
		</id>
		<property name="idCard" />
		<one-to-one name="person"/>
	</class>
</hibernate-mapping>

 

public class Card {
	private int id;
	private String idCard;
	private Person person;
	public Person getPerson() {
		return person;
	}
	public void setPerson(Person person) {
		this.person = person;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getIdCard() {
		return idCard;
	}
	public void setIdCard(String idCard) {
		this.idCard = idCard;
	}
}

   其它的不变。以card作为主的一方，只能进行查询person，而不能级联的改变person。

3.一对一唯一外键关联（单向关联）

    一对一唯一外键关联实际上是多对一关联映射的特例

   可以采用<many-to-one>标签，指定多的一端unique="true"，即限制了多的一端的多重性为一。

    (person.hbm.xml)

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.yyming.hibernate.Person">
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="name" />
		<many-to-one name="card" unique="true"/>
	</class>
</hibernate-mapping>

    (Card.hbm.xml)

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
	<class name="com.yyming.hibernate.Card">
		<id name="id">
			<generator class="native" />
		</id>
		<property name="cardNo" />
	</class>
</hibernate-mapping>