欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页

hibernate之一对一关联映射

程序员文章站 2022-04-16 09:25:22
...

Hibernate的一对一关联映射分为:

  • 主键映射:

一对一的主键关联,就是两张表通过主键形成一对一关系,并且两张表共享一个主键;

实例:

        一个人只能拥有一张身份证,同时一张身份证也只能属于它的一个主人;人和身份证就拥有同一个主键;

TPerson:

public class TPerson implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer id;
	private String name;
	private TCard tcard;
        get()/set()
}

 TPerson.hbm.xml:

<hibernate-mapping package="com.keith.one2one.pk">
	<class name="TPerson" table="TPerson">			
		<id name="id">
			<generator class="native">
			</generator>
		</id>
		
		<property name="name" />
		<!-- 
			通过one-to-one节点,将TPerson与TCard类相关联 ;
			cascade="all" 级联关系,当主控方发生操作或改变的时候,关联对象也会执行同一动作;
			outer-join="true" 外连接;
		-->
		<one-to-one name="tcard" class="com.keith.one2one.pk.TCard" cascade="all" outer-join="true"/>
	</class>	
</hibernate-mapping>
 

 

TCard:

public class TCard implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer cardId;
	private String num;
	private TPerson tperson;
        get()/set()
}

 TCard.hbm.xml:

<hibernate-mapping package="com.keith.one2one.pk">
	<class name="TCard" table="TCard">			
		<id name="cardId">
		<!-- 
			由于采用了主键关联方式,那么通过主键关联的两个表,其关联记录的主键值必须保持同步,
			意味着,我们只需为一张表设定主键生成器,而另一张表与之共享即可;
		 -->
			<generator class="foreign">
				<param name="property">tperson</param>
			</generator>
		</id>
		
		<property name="num" />
		<!-- 
			constrained:约束,告知Hibernate当前表主键上存在一个约束;
		 -->
		<one-to-one name="tperson" class="com.keith.one2one.pk.TPerson" constrained="true"/>
	</class>	
</hibernate-mapping>

测试代码:添加数据:

		TPerson person = new TPerson();
		person.setName("keith");
		
		TCard card = new TCard();
		card.setNum("10101010101");
		
		person.setTcard(card);
		card.setTperson(person);
		
		session.save(person);
		session.save(card);

 查询数据:

		TPerson person = (TPerson) session.load(TPerson.class, new Integer(1));
		System.out.println("person's name:"+person.getName());
		System.out.println("person's cardNum:"+person.getTcard().getNum());

 删除数据:

		TPerson person = (TPerson) session.load(TPerson.class, new Integer(1));
		System.out.println("person's name:"+person.getName());
		System.out.println("person's cardNum:"+person.getTcard().getNum());
 
  • 唯一外键映射;

通过外键与其进行关联;

实例:

用户和组的关系;一个用户属于一个组,一个组里有用户;

TUser:

public class TUser implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer userid;
	private String name;
	private TGroup group;
        get()/set()
}

TGroup:

public class TGroup implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer groupId;
	private String name;
        get()/set()
}

 TUser.hbm.xml:

<hibernate-mapping package="com.keith.one2one.fk.uni">
	<class name="TUser" table="TUser">			
		<id name="userid">
			<generator class="native"/>
		</id>
	
		<property name="name" />
		<!-- 
		唯一外键关联的一对一关系,是特殊的多对一关系;
		所以用many-to-one标签;并且加上unique并设置其值为true;
		-->
		<many-to-one name="group" class="TGroup" column="group_id" unique="true"/>
	</class>	
</hibernate-mapping>

 TGroup.hbm.xml:

<hibernate-mapping package="com.keith.one2one.fk.uni">
	<class name="TGroup" table="TGroup">			
		<id name="groupId">
			<generator class="native"/>
		</id>
	
		<property name="name" />	
	</class>	
</hibernate-mapping>

 以上只是单向关系,如果要设置成双向关系,则在TGroup中加入TUser对象,且加上get()/set(),在TGroup.hbm.xml中加上:

<one-to-one name="user" class="TUser" property-ref="group"/>

 标签;

TGroup:

public class TGroup implements java.io.Serializable {
	private static final long serialVersionUID = 1L;

	private Integer groupId;
	private String name;
	private TUser user;
        get()/set()
}

 TGroup.hbm.xml:

<hibernate-mapping package="com.keith.one2one.fk.doubleSide">
	<class name="TGroup" table="TGroup">			
		<id name="groupId">
			<generator class="native"/>
		</id>
	
		<property name="name" />
		<one-to-one name="user" class="TUser" property-ref="group"/>	
	</class>	
</hibernate-mapping>

 附件上有测试代码和实例代码;

 

相关标签: Hibernate XML