hibernate雙向一對一主鍵關聯對映XML與註解版
阿新 • • 發佈：2019-02-01
雙向一對一關聯對映原理:
雙向的主鍵關聯其實是單向一對一主鍵關聯的一種特殊情況，只不過要在關聯物件的兩端的對映檔案中都要進行<one-to-one>的配置，另外還要在主對映的主鍵一端採用foreign外來鍵關聯屬性。
這裡同樣使用Person和IdCard來討論，一個人對應著一個唯一的身份證，而且一個身份證也唯一對映著一個人，所以這就產生了雙向的關聯關係，Person的主鍵同樣也是IdCard的主鍵，分別是主鍵的同時也是外來鍵，這種關聯關係成為雙向一對一對映，表現到關係模型中可如下圖：
(1)XML版
SQL檔案:
CREATE TABLE `person` ( `id` varchar(255) NOT NULL, `pname` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE `idcard` ( `id` varchar(255) NOT NULL, `cardnum` varchar(255) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8;
Person類:
package Hibernate_demo1.Demo11.Entity; public class Person { private String id; private String pname; private IdCard idcards; public String getId() { return id; } public void setId(String id) { this.id = id; } public String getPname() { return pname; } public void setPname(String pname) { this.pname = pname; } public IdCard getIdcards() { return idcards; } public void setIdcards(IdCard idcards) { this.idcards = idcards; } }
IdCard類:
package Hibernate_demo1.Demo11.Entity; public class IdCard { private String id; private String cardNum; private Person persons; public Person getPersons() { return persons; } public void setPersons(Person persons) { this.persons = persons; } public String getId() { return id; } public void setId(String id) { this.id = id; } public String getCardNum() { return cardNum; } public void setCardNum(String cardNum) { this.cardNum = cardNum; } }
IdCard.hbm.xml對映檔案
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Hibernate_demo1.Demo11.Entity.IdCard" table="IdCard">
<id name="id" type="java.lang.String">
<column name="id"/>
<generator class="uuid">
</generator>
</id>
<property name="cardNum" column="cardNum"/>
<!--
在對映檔案中新增外來鍵屬性persons，並新增對應的<one-to-one>標籤
目的是強制約束person類來實現一對一的對映關係，最後在對映中將constrained屬性設為true
保證強制約束關係。
-->
<one-to-one name="persons" constrained="true"></one-to-one>
</class>
</hibernate-mapping> 雙向一對一唯一外來鍵對映關鍵對映程式碼——在IdCard端新加入如下標籤對映：
<one-to-one name="person"property-ref="idCard"/> 注意：一對一唯一外來鍵關聯雙向採用<one-to-one>標籤對映，必須指定<one-to-one>標籤中的property-ref屬性為關係欄位的名稱。
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Hibernate_demo1.Demo11.Entity.Person" table="person">
<id name="id">
<generator class="uuid">
</generator>
</id>
<property name="pname" column="pname"/>
<!--
one-to-one標籤指示Hibernate如何載入其關聯物件，預設根據主鍵載入，也就是拿到關係欄位值，根據對端的主鍵來載入關聯物件
-->
<one-to-one name="idcards"></one-to-one>
</class>
</hibernate-mapping> 測試類:
package Hibernate_demo1.Demo11;
import org.hibernate.Session;
import Hibernate_demo1.Demo11.Entity.IdCard;
import Hibernate_demo1.Demo11.Entity.Person;
import Hibernate_demo1.Demo11.Util.HibernateUtils;
public class App
{
public static void main( String[] args )
{
Session session = null;
try{
session = HibernateUtils.getSession();
session.beginTransaction();
//建立person物件，並儲存
Person person=new Person();
person.setPname("fendo");
session.save(person);
//建立idCard物件，並儲存
IdCard idcard=new IdCard();
idcard.setCardNum("123456789");
idcard.setPersons(person);
session.save(idcard);
session.getTransaction().commit();
}catch(Exception e){
e.printStackTrace();
session.getTransaction().rollback();
}finally{
HibernateUtils.closeSession(session);
}
}
}
執行結果如下:
Hibernate:
insert
into
person
(pname, id)
values
(?, ?)
Hibernate:
insert
into
IdCard
(cardNum, id)
values
(?, ?)執行結果如下:
Person表
idcard表
(2)註解版
Person類:
package Hibernate_demo1.Demo12.Entity;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
import org.hibernate.annotations.GenericGenerator;
@Entity
@Table(name="person")
public class Person {
@Id
@GenericGenerator(name="uuidGenerator", strategy="uuid")
@GeneratedValue(generator="uuidGenerator")
private String id;
@Column(name="pname")
private String pname;
@OneToOne(cascade=CascadeType.ALL)
@PrimaryKeyJoinColumn
private IdCard idcards;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public IdCard getIdcards() {
return idcards;
}
public void setIdcards(IdCard idcards) {
this.idcards = idcards;
}
}
IdCard類:
package Hibernate_demo1.Demo12.Entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToOne;
import javax.persistence.PrimaryKeyJoinColumn;
import javax.persistence.Table;
import org.hibernate.annotations.GenericGenerator;
@Entity
@Table(name="idcard")
public class IdCard {
@Id
@GenericGenerator(name="uuidGenerator", strategy="uuid")
@GeneratedValue(generator="uuidGenerator")
private String id;
@Column(name="cardNum")
private String cardNum;
@OneToOne
@PrimaryKeyJoinColumn
private Person persons;
public Person getPersons() {
return persons;
}
public void setPersons(Person persons) {
this.persons = persons;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getCardNum() {
return cardNum;
}
public void setCardNum(String cardNum) {
this.cardNum = cardNum;
}
}
測試類:
package Hibernate_demo1.Demo12;
import java.util.HashSet;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;
import Hibernate_demo1.Demo12.Entity.IdCard;
import Hibernate_demo1.Demo12.Entity.Person;
public class App
{
public static void main( String[] args )
{
SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();
Session session = sessionFactory.getCurrentSession();
Transaction tx = session.beginTransaction();
//建立person物件，並儲存
Person person=new Person();
person.setPname("fendo");
session.save(person);
//建立idCard物件，並儲存
IdCard idcard=new IdCard();
idcard.setCardNum("123456789");
idcard.setPersons(person);
session.save(idcard);
tx.commit();
session.close();
}
}
執行結果如下:
Hibernate:
insert
into
person
(pname, id)
values
(?, ?)
Hibernate:
insert
into
idcard
(cardNum, id)
values
(?, ?)