主表和从表的一对一设置

利用hibernate 设置数据库的关联；

主类：

public class Person {
	private Integer id;
	private String name;
	private int age;
	private Address address;
	
//************************************系统自动创建区**************************************
	public Person(){}
	
	public Person(String name, int age) {
		super();
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString() {
		return "Person [id=" + id + ", name=" + name + ", age=" + age + "]";
	}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public Address getAddress() {
		return address;
	}
	public void setAddress(Address address) {
		this.address = address;
	}
}

主类的配置文件：

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
  PUBLIC "-//Hibernate?Hibernate Mapping DTD//EN"
  "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="relevance">

  <class name="Person" table="relevance" dynamic-update="true">
    <id name="id">
    	<generator class="native"></generator></id>
    <property  name="name"/>
    <property name="age"/>
    <one-to-one name="address"></one-to-one>
  </class>
</hibernate-mapping>

从类：

public class Address {
	
	private Integer id;
	private String city;
	private int postcode;
	private Person person;
	
//************************************系统自动创建区**************************************
	public Address(){}
	
	public Address(String city, int postcode) {
	super();
	this.city = city;
	this.postcode = postcode;
}
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public Person getPerson() {
		return person;
	}
	public void setPerson(Person person) {
		this.person = person;
	}
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public int getPostcode() {
		return postcode;
	}
	public void setPostcode(int postcode) {
		this.postcode = postcode;
	}
	@Override
	public String toString() {
		return "Address [id=" + id + ", city=" + city + ", postcode=" + postcode + "]";
	}
}

从类的配置文件：该关联是基本的primary key one 2 one 的设置；

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping
  PUBLIC "-//Hibernate?Hibernate Mapping DTD//EN"
  "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="relevance">

  <class name="Address" table="relevance_address" dynamic-update="true">
    <id name="id">
    	<generator class="native"></generator></id>
    <property  name="city"/>
    <property name="postcode"/>
    <many-to-one name="person" column="person_id" unique="true" not-null="true"></many-to-one>
  </class>
  
</hibernate-mapping>

如果改为关联是foreign key one 2 one 的设置则只需要修改从表的配置文件，其他完全不变：

  <class name="Address" table="relevance_address" dynamic-update="true">
    <id name="id">
    
        <!--Pay attention to here ! -->
    
    	<generator class="foreign">
    	
    	<!-- Set the associated param : Address.person ;  -->
    	
    	<param name="property">person</param> </generator></id>
    <property  name="city"/>
    <property name="postcode"/>
    
    <!--Pay attention to here ! -->
    <one-to-one name="person" constrained="true"></one-to-one>
  </class>

测试类：

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

public class ForTest {
	Session session;
	Transaction tx;
	SessionFactory sessionFactory;
	@Before
	public void setUp() throws Exception {
		System.out.println("------------数据初始化--------------");
		Configuration config = new Configuration().configure("relevance/hibernate.cfg.xml");
		sessionFactory = config.buildSessionFactory();
		session = sessionFactory.openSession();
		tx = session.beginTransaction();
	}

	@After
	public void tearDown() throws Exception {
		System.out.println("------------数据释放--------------");
		tx.commit();
		if(session.isOpen()) session.close();
		sessionFactory.close();
	}

	@Test
	public void test() {
		Address address = new Address("Shanghai.China",0551);
		session.persist(address);
	}
	@Test
	public void testone2noe(){
		Person person = new Person("Adim",30);
		Address address = new Address("Shanghai.China",0551);
		//这里很有趣，存入数据库以后，0551变成了361，估计是因为数据库中0开头表示八进制吧；
		person.setAddress(address);
		address.setPerson(person);
	/* 注意这里，因为address是从表，且设定了not-null，因此person必须要先于address添加到库中
	 * 即，下面的书写顺序不能有变化；如果不设定not-null，则顺序变化也可以存入，但是会多一步操
	 * 作，影响性能，不建议；*/		
		session.persist(person);
		session.persist(address);
	}
	@Test
	public void testQuery_from_SlaveTable(){
		Address address = session.load(Address.class, 1);
				System.out.println(address);
				System.out.println("------------------");
				System.out.println(address.getPerson());
	}
	@Test
	public void testQuery_from_MasterTable(){
		Person person = session.load(Person.class, 1);
				System.out.println(person);
				System.out.println("------------------");
				System.out.println(person.getAddress());
	}
}

testQuery_from_SlaveTable 的测试的结果如下：

Hibernate: select address0_.id as id1_1_0_, address0_.city as city2_1_0_, address0_.postcode as postcode3_1_0_, address0_.person_id as person_i4_1_0_ from relevance_address address0_ where address0_.id=?
Address [id=1, city=Shanghai.China, postcode=361]
------------------
Hibernate: select person0_.id as id1_0_0_, person0_.name as name2_0_0_, person0_.age as age3_0_0_, address1_.id as id1_1_1_, address1_.city as city2_1_1_, address1_.postcode as postcode3_1_1_, address1_.person_id as person_i4_1_1_ from relevance person0_ left outer join relevance_address address1_ on person0_.id=address1_.id where person0_.id=?
Person [id=1, name=Adim, age=30]
------------数据释放--------------

可以看到，在一次测试中，hibernate发起了2次Query 请求，第一次是因为获取从表，但是在输出从表数据时，没有涉及person属性，所以没有加载person，但是当

需要打印person属性时，则重新发出了Query.

testQuery_from_MasterTable的测试结果如下：

Hibernate: select person0_.id as id1_0_0_, person0_.name as name2_0_0_, person0_.age as age3_0_0_, address1_.id as id1_1_1_, address1_.city as city2_1_1_, address1_.postcode as postcode3_1_1_, address1_.person_id as person_i4_1_1_ from relevance person0_ left outer join relevance_address address1_ on person0_.id=address1_.id where person0_.id=?
Person [id=1, name=Adim, age=30]
------------------
Address [id=1, city=Shanghai.China, postcode=361]
------------数据释放--------------

可以明显的看出来，这里只进行了一次Query，说明load主表时，从表被自动加载了