Hibernate one to one 关联关系映射

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一个销售员salesman对应一个地址Address：

 

1.数据库建表SQL：

use test;
create table salesman3(sid int not null primary key, salesName varchar(20));
create table address(aid int not null primary key, province varchar(20),city varchar(20),street varchar(20),gatenumber int, foreign key(aid) references salesman(sid));

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2.model：

Salesman.java:

package ie.basicCar3.bean;

 

public class Salesman implements java.io.Serializable{
 private long sid;

 private String salesName;
 
 private Address saddress; 
 
 public Salesman() {
 }

 public Salesman(String salesname, Address a) {
  this.salesName = salesname;
  this.saddress = a;
 }

//省略了getter setter方法
}

 

Address.java:

package ie.basicCar3.bean;

public class Address  implements java.io.Serializable{
  private long aid;

 private String province; 
 private String city;
 private String street;
 private int gatenumber;
 private Salesman salesman;
 public Address(){
 }
 public Address(String p, String c, String s,int n){
  this.province=p;
  this.city=c;
  this.street=s;
  this.gatenumber=n;
 }

//省略了getter setter方法
}

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3.Hibernate映射文件：

Salesman.hbm.xml:

 

<hibernate-mapping>
  <class name="ie.basicCar3.bean.Salesman" table="salesman3" lazy="false">
   <id column="sid" name="sid" type="long">
    <generator class="increment"></generator>
   </id>
   <property name="salesname" column="salesname" type="string">
   </property>
   <one-to-one
   name="saddress"
   class="ie.basicCar3.bean.Address"
   cascade="all"
   ></one-to-one>
   </class>
</hibernate-mapping>

 

Address.hbm.xml:

 

<hibernate-mapping>
  <class name="ie.basicCar3.bean.Address" table="address" lazy="false">
   <id name="aid" column="aid" type="long">
    <generator class="foreign">
    <param name="property">salesman</param>
    </generator>
   </id>
   <property name="province" column="province" type="string">
   </property>
   <property name="city" column="city" type="string">
   </property>
   <property name="street" column="street" type="string">
   </property>
   <property name="gatenumber" column="gatenumber" type="int">
   </property>
   <one-to-one
   name="salesman"
   class="ie.basicCar3.bean.Salesman"
   constrained="true"
   cascade="save-update">
   </one-to-one>
</class>
</hibernate-mapping>

 

 

在上面的映射文件中，特别注意主键的生成方式为foreign。使用foreign作为标识符生成器，说明这个主键同时也作为外键，依赖于另一个相关联表的主键，所以需要<param>元素来制定要关联的实体。

constrained属性为true，说明address表的id主键同时作为外键参照salesman表。这个选项影响save()和delete()在级联执行时的先后顺序，其默认是false。

其它属性的含义与一对多里的相同。

 

单向一对一，则只配置其中一部分，同时根据实际需要，注意选择cascade的属性值。

 

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4.测试类：

 

package ie.basicCar3;

import java.sql.Date;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;

import ie.basicCar3.bean.Address;
import ie.basicCar3.bean.Salesman;

public class Test {

 Configuration  cfg;
 SessionFactory sf;
 Session session;
 
 public static void main(String[] args) {

  Test test=new Test();
  test.DoConfiguration();
  //test.saveEntity();
  test.updateEntity();
  //test.deleteEntity();
  System.out.println("end");
 }

 void DoConfiguration(){
//  new a configuration and read the configuration from the given path
  cfg = new Configuration();
  cfg.configure("ie/basicCar3/hibernate.cfg.xml");

  //use the properites in the configure file to new a sessionFactory
  sf = cfg.buildSessionFactory();
 }
 
 void saveEntity() {
//  new a session from sessionfactory
  session = sf.openSession();
  //  save a BasicCar in database
  Transaction tx1 = session.beginTransaction();
  Address ad = new Address("guangdong3", "guangzhou", "dexing", 104);
  Salesman ss = new Salesman("bbb78", ad);
  //不管设置了cascade还是没有，保存了一个，都会自动保存另一个,写任何一个的save,或者两个，都是两个表都保存一下
  ad.setSalesman(ss);
  //ss.setSaddress(ad);
  //session.save(ss);
  session.save(ad);
  //  System.out.println(bc1.getFactory());
  tx1.commit();
  
  //close session
  session.close();
 }

 void deleteEntity() {
//  new a session from sessionfactory
  session = sf.openSession();
  //delete the id=1 basicCar Object from database
  Transaction tx3 = session.beginTransaction();
  try {
   //Address add = (Address) session.load(Address.class, new Long(12));
   //如果address.hbm.xml有cascade="delete"，那么可以连着把salesman也删除，否则只删除address
   //session.delete(add);

   Salesman sas = (Salesman) session.load(Salesman.class, new Long(4));
   //由于foreign key约束不能只是删salesman，而不删除address
   //如果salesman.hbm.xml没有cascade="delete"，但是因为数据库里有foreign key约束，所以会报错Cannot delete or update a parent row: a foreign key constraint fails
  // session.delete(sas.getSaddress());
   session.delete(sas);

  } catch (Exception e) {
   System.out.println("id=1 car are not existed, can't be deleted");
  }
  tx3.commit();
  //close session
  session.close();
 }

 void updateEntity() {
//  new a session from sessionfactory
  session = sf.openSession();
  //update the name of besicCar above into databas
  Transaction tx2 = session.beginTransaction();
  Address a1 = (Address) session.load(Address.class, new Long(1));
  
  //a1.getSalesman().setSalesname("gagagaga");

  session.update(a1);

  
  //Salesman sas2 = (Salesman) session.load(Salesman.class, new Long(4));
  //sas2.getSaddress().setCity("nanjing2");
  
  //session.update(sas2);
  
  tx2.commit();
  
  //close session
  session.close();
 }

 void queryEntity() {
//  new a session from sessionfactory
  session = sf.openSession();
  //  query a car from database
  /* try{
   Query query=session.createQuery("from BasicCar");
   BasicCar bc3=(BasicCar)query.list().get(0);
   System.out.println("name for the first selected car is: "+bc3.getName());
   }catch (Exception e)
   {
   System.out.println("no car in database");
   }*/

  //close session
  session.close();
 }
 
}

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5.导入Hibernate jar包，jdbc驱动，再加一个Hibernate配置文件(如下），就可以用运行测试类，一对多配置完成，可以根据实际需求调整相应的映射文件。

hibernate.cfg.xml:

<hibernate-configuration>
    <session-factory>
        <property name="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
        <property name="hibernate.connection.password">embed</property>
        <property name="hibernate.connection.url">jdbc:oracle:thin:@192.168.100.231:1521:typt</property>
        <property name="hibernate.connection.username">dbcdc</property>
        <property name="hibernate.dialect">org.hibernate.dialect.Oracle9iDialect</property>
        <!--  mapping resource="basicCar/bean/BasicCar1.hbm.xml"/-->
        <mapping resource="ie/basicCar3/bean/Address.hbm.xml"/>
        <mapping resource="ie/basicCar3/bean/Salesman.hbm.xml"/>
    </session-factory>
</hibernate-configuration>