Hibernate 一对一

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hibernate一对一例子-已更新（一）
先看由满江红翻译团队(RedSaga Translate Team)翻译的一对一配置说明
一对一

持久化对象之间一对一的关联关系是通过one-to-one元素定义的。

<one-to-one
        name="propertyName"                                          (1)
        class="ClassName"                                            (2)
        cascade="cascade_style"                                      (3)
        constrained="true|false"                                     (4)
        fetch="join|select"                                          (5)
        property-ref="propertyNameFromAssociatedClass"               (6)
        access="field|property|ClassName"                            (7)
        formula="any SQL expression"                                 (8)
        lazy="true|proxy|false"                                      (9)
        entity-name="EntityName"                                     (10)
        node="element-name|@attribute-name|element/@attribute|."
        embed-xml="true|false"
/>
(1) name: 属性的名字。

(2) class (可选 - 默认是通过反射得到的属性类型)：被关联的类的名字。

(3) cascade(级联) (可选) 表明操作是否从父对象级联到被关联的对象。

(4) constrained(约束) (可选) 表明该类对应的表对应的数据库表，和被关联的对象所对应的数据库表之间，通过一个外键引用对主键进行约束。 这个选项影响save()和delete()在级联执行时的先后顺序以及 决定该关联能否被委托(也在schema export tool中被使用).

(5) fetch (可选 - 默认设置为选择): 在外连接抓取或者序列选择抓取选择其一.

(6) property-ref: (可选) 指定关联类的属性名，这个属性将会和本类的主键相对应。如果没有指定，会使用对方关联类的主键。

(7) access (可选 - 默认是 property): Hibernate用来访问属性的策略。

(8) formula (可选):绝大多数一对一的关联都指向其实体的主键。在一些少见的情况中， 你可能会指向其他的一个或多个字段，或者是一个表达式，这些情况下，你可以用一个SQL公式来表示。 （可以在org.hibernate.test.onetooneformula找到例子）

(9) lazy (可选 - 默认为 proxy): 默认情况下，单点关联是经过代理的。lazy="true"指定此属性应该在实例变量第一次被访问时应该延迟抓取（fetche lazily）（需要运行时字节码的增强）。 lazy="false"指定此关联总是被预先抓取。注意，如果constrained="false", 不可能使用代理，Hibernate会采取预先抓取！

(10) entity-name (可选): 被关联的类的实体名。

具体配置可以看
http://www.huihoo.com/framework/hibernate/reference-v3_zh-cn/mapping.html
好。。再来测试。。。
1.建表
create   table  student
(sid  varchar ( 32 )  not   null   primary   key ,
sname  varchar ( 16 ),
sage  varchar ( 16 )
)
create   table  address
(aid  varchar ( 32 )  not   null   primary   key ,
acity  varchar ( 16 ),
aroad  varchar ( 16 )
)
2.写VO
   Address vo
package com.test;

public class Address
{
    private String aid;
    private String acity;
    private String aroad;
    private Student student;
  //写上GET SET方法
Student vo
package com.test;
public class Student
{
    private String sid;
    private String sname;
    private String sage;
    private Address address;
//写上get set
3.写配置文件
Student.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
    PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

    <class name="com.test.Student" table="student" >

        <id name="sid" type="string" unsaved-value="null" >
            <column name="sid" sql-type="char(32)" not-null="true"/>
            <generator class="uuid.hex"/>
        </id>

        <property name="sname">
            <column name="sname" sql-type="varchar(16)" />
        </property>

        <property name="sage">
            <column name="sage" sql-type="varchar(16)" />
        </property>

        <one-to-one name="address" class="com.test.Address" cascade="all"/>
  
    </class>

</hibernate-mapping>Address.hbm.xml
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
    PUBLIC "-//Hibernate/Hibernate Mapping DTD//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd">

<hibernate-mapping>

    <class name="com.test.Address" table="address" >

        <id name="aid" type="string" unsaved-value="null" >
            <column name="aid" sql-type="char(32)" not-null="true"/>
            <generator class="foreign">
                <param name="property">student</param>
            </generator>
        </id>

        <property name="acity">
            <column name="acity" sql-type="varchar(16)" />
        </property>

        <property name="aroad">
            <column name="aroad" sql-type="varchar(16)" />
        </property>

        <one-to-one name="student" class="com.test.Student"/>

    </class>

</hibernate-mapping>
接着把下面的hibernate.properties文件拷到classes目录下。。这里用的是mysql
hibernate.query.substitutions true 1, false 0, yes 'Y', no 'N'
## MySQL
hibernate.dialect net.sf.hibernate.dialect.MySQLDialect
hibernate.connection.driver_class org.gjt.mm.mysql.Driver
hibernate.connection.url jdbc:mysql://localhost:3306/wjcms
hibernate.connection.username root
hibernate.connection.password wujun
hibernate.connection.pool_size 1
hibernate.proxool.pool_alias pool1
hibernate.show_sql true
hibernate.jdbc.batch_size 0
hibernate.max_fetch_depth 1
hibernate.cache.use_query_cache true 4.写测试类了..

package com.test;

import net.sf.hibernate.Session;
import net.sf.hibernate.SessionFactory;
import net.sf.hibernate.cfg.Configuration;
import net.sf.hibernate.*;
import java.sql.*;
import java.util.List;

public class TestOneToOne
{
    SessionFactory sf;
    Session session;
    public TestOneToOne()
    {
        try
        {
            Configuration cfg = new Configuration();
            sf = cfg.addClass(Student.class).addClass(Address.class).buildSessionFactory();
        }
        catch(HibernateException ex)
        {
            ex.printStackTrace();
        }
    }
    public void doCreate()
    {
        try
        {
            session = sf.openSession();

            Student student = new Student();
            student.setSname("小王");
            student.setSage("22");

            Address address = new Address();
            address.setAcity("深圳");
            address.setAroad("深南");
            address.setStudent(student);
            student.setAddress(address);

            session.save(student);
            session.flush();
            session.connection().commit();

        }
        catch(HibernateException ex)
        {
            ex.printStackTrace();
        }
        catch(SQLException ex1)
        {
            ex1.printStackTrace();
        }
        finally
        {
                try{
                    session.close();
                }
                catch(HibernateException ex2){
                }
        }

    }
    public void doQuery()
    {
        try{
            session = sf.openSession();
            Query q = session.createQuery("select s from Student as s");
            List l = q.list();
            Student s = null;
            Address address = null;
            for(int i=0;i<l.size();i++)
            {
                s = (Student)l.get(i);
                System.out.println("姓名： "+s.getSname());
                System.out.println("年龄： "+s.getSage());
                address = s.getAddress();
                System.out.println("住址:  "+address.getAcity()+address.getAroad());
            }

        }
        catch(HibernateException ex){
            ex.printStackTrace();
        }
        finally{
            try{
                session.close();
            }
            catch(HibernateException ex2){
            }
        }
    }
    public static void main(String[] args)
    {
        TestOneToOne t = new TestOneToOne();
        //t.doCreate();
        t.doQuery();
    }
}