Hibernate 关系映射(五) 基于主键关联的单向1:1

1.单向 1:1 基于主键关联
想象下 小康社会: 每家都有钱, 住起了小洋房 ,洋房编号:  xx村2-36

eg:  一个地方有 一个人住.或者说 一家人住
eg:  每个同学家庭请了单独家教老师, 这样 1 对 1 的辅导
(在 原本N　变成了　1 的一端进行配置) 

1 (N)          1
Person   : Address
Student  : Teacher


注意:基于主键关联,说的是Person表中id的值是Address表中的id


person



address

public class Address {
	private Integer aid;
	private String addressDetail;

        //set get ...
}

public class Person {

	private Integer pid;
	private String name;
	private int age;
	
	private Address address;  //单向(N:1)  反过来(1:1) 
	//set  get...
}

--基于主键关联的  1:1 关系 
DROP TABLE IF EXISTS mytest.person;

CREATE TABLE mytest.person
	(
	PID  INT NOT NULL,
	NAME VARCHAR (255),
	AGE  INT,
	PRIMARY KEY (PID)
	);
DROP TABLE IF EXISTS mytest.address;

CREATE TABLE mytest.address
	(
	AID         INT NOT NULL,
	ADDRESSDESC VARCHAR (255),
	PRIMARY KEY (AID)
	);

   <!--person-->
  <hibernate-mapping package="com.sh.study.model.o2o">
	<class name="Person" table="PERSON">
		<!-- 基于主键的 1:1  -->
		<id name="pid" type="java.lang.Integer" column="PID">
			<generator class="foreign" >
				<param name="property">address</param>
			</generator>
		</id> 
                <one-to-one name="address" cascade="all"/>

		<property name="name" type="java.lang.String">
			<column name="NAME" />
		</property>
		<property name="age" type="int">
			<column name="AGE" />
		</property>
		
		
		
		<!-- 基于外键的　单向　1:1   注意 cascade-->
		<!-- unique="true"  表示 N　的一端必须是　唯一即可　这样就变成　　单向　1:1　
		<many-to-one name="address" unique="true" cascade="all"
			class="Address" column="address_id">
		</many-to-one>
		　 -->
		
		<!-- 基于中间表的  1:1 关系
		<join table="person_address">
			<key column="person_id"/>
			<many-to-one name="address" cascade="all" unique="true" class="Address" column="address_id"/>
		</join>
		-->
	</class>
</hibernate-mapping>


   <!--address-->
  <hibernate-mapping package="com.sh.study.model">
	<class name="Address" table="ADDRESS">
		<id name="aid" type="java.lang.Integer" column="AID">
			<generator class="increment"/>
		</id> 
		<property name="addressdesc" type="java.lang.String">
			<column name="ADDRESSDESC" />
		</property>
	</class>
</hibernate-mapping>

//test

public class TestHibernate {
	private ApplicationContext act;
	private SessionFactory factory;
	@Before
	public void init(){
		act = new ClassPathXmlApplicationContext("classpath:spring/applicationContext.xml");
		factory= act.getBean("sessionFactory",SessionFactory.class);
	}
//修改 Person的地址
	@Test
	public void test1() {
		try {
		
			Session session=factory.getCurrentSession();
			Transaction tx=session.beginTransaction();
			Person p=new Person();
			p.setAge(12);
			p.setName("Yeeku");
			Address address=new Address();
			address.setAddressdesc("北京海淀区");
			p.setAddress(address);
	
			//持久化对象
			session.persist(p);
			//修改 Person的 地址 发现采用这种不行,因为此时 Address多家了一条数据,但是person的地址没有改变,也就是id没有变
			Address address1=new Address();
			address1.setAddressdesc("上海虹口");
			p.setAddress(address1);
			session.flush();

			System.out.println(p.getAddress().getAddressdesc());
			Person pp=(Person)session.load(Person.class,1);
			System.out.println(pp.getAddress().getAddressdesc());
			tx.commit();
			
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

//修改person的地址信息,此时修改Address对象就没有问题
@Test
	public void test2() {
		try {
		
			Session session=factory.getCurrentSession();
			Transaction tx=session.beginTransaction();
			Person p=new Person();
			p.setAge(12);
			p.setName("Yeeku");
			Address address=new Address();
			address.setAddressdesc("北京海淀区");
			p.setAddress(address);
	
			//持久化对象
			session.persist(p);
			//修改 Person的 地址
//数据库中不会添加一条数据
			address.setAddressdesc("上海虹口");
		

			session.flush();
			System.out.println(p.getAddress().getAddressdesc());
			Person pp=(Person)session.load(Person.class,1);
			System.out.println(pp.getAddress().getAddressdesc());
			tx.commit();
			//  发现 地址是重新添加入了一个    此时数据库中有两个Address  一个 Person有以前的地址1 变成了 2
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

//同一个地址添加两个人会报错

@Test
	public void test3() {
		try {
		
			Session session=factory.getCurrentSession();
			Transaction tx=session.beginTransaction();
			Person p=new Person();
			p.setAge(12);
			p.setName("Yeeku");
			Address address=new Address();
			address.setAddressdesc("北京海淀区");
			p.setAddress(address);
	
			//持久化对象
			session.persist(p);
			//修改 Person的 地址
			address.setAddressdesc("上海虹口");
		
//如果一个地址添加了多个人 就会报错 
			/*Person p1=new Person();
			p1.setAge(21);
			p1.setName("luck");
			p1.setAddress(address);
			session.persist(p1);*/
			
			session.flush();
			System.out.println(p.getAddress().getAddressdesc());
			Person pp=(Person)session.load(Person.class,1);
			System.out.println(pp.getAddress().getAddressdesc());
			tx.commit();
			
			
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	
	
}

如果一个地址 被多个person引用,此时会出问题,因为Person表中出现有多个相同的id

org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.sh.study.model.o2o.Person#2]