java鬼混笔记：Hibernate：2、一对一关系之主键单向和双向关联
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2022-04-22 16:10:15
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这次的笔记是Hibernate的一对一关系操作的，什么是一对一，比如一个人对应一个身份证，一个国家一个星爷，一个手指一个指纹等等。。。都是一对一的。
知识点：一对一主键关联（单向），一对一主键关联（双向）。（主键关联：比如person表的ID是card表的id的意思，两张表通过ID相同获取数据）
一对一外键关联（单向）， 一对一外键关联（双向）（外键关联：比如card表中有个字段pid对应的是person表中的id,通过card.person.id = person.id去获取相关的数据）
什么是单向：只能由A访问到B，而不能从B访问A;双向就是A和B都相互访问
接下来上实例代码:
比如有个用户Person和身份证Card
单向关联：
Persondx.java
package com.ywj.TestHibernate.e;
import java.io.Serializable;
// 一个人 Persondx 后面的dx是单向的意思
public class Persondx implements Serializable{
/**
*
*/
private static final long serialVersionUID = -3189538608590684635L;
private Long id;
private String name;
private Carddx carddx;// 他的身份证
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Carddx getCarddx() {
return carddx;
}
public void setCarddx(Carddx carddx) {
this.carddx = carddx;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.ywj.TestHibernate.e">
<class name="Persondx" table="Persondx" >
<id name="id" column="id">
<generator class="foreign">
<param name="property">carddx</param> <!-- person的id是根据card的id来设置的 一对一嘛 -->
</generator>
</id>
<property name="name" column="name" type="java.lang.String"/>
<!-- 一对一设置 constrained="true" 进行约束操作 persondx表的个外键，参考表carddx.id -->
<one-to-one name="carddx" class="Carddx" constrained="true"></one-to-one>
</class>
</hibernate-mapping>
package com.ywj.TestHibernate.e;
import java.io.Serializable;
// Carddx 后面的dx是单向的意思
public class Carddx implements Serializable {
private static final long serialVersionUID = -5428059743879860845L;
private Long id;
private String number;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
}
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.ywj.TestHibernate.e">
<class name="Carddx" table="carddx" >
<id name="id" column="id">
<generator class="identity" /><!-- card ID就自动增长，Person再根据Card ID 保存ID -->
</id>
<property name="number" column="number" type="java.lang.String"/>
</class>
</hibernate-mapping>测试Demo:
TestOneToOnedx.java
package com.ywj.TestHibernate.test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.ywj.TestHibernate.e.Carddx;
import com.ywj.TestHibernate.e.Persondx;
public class TestOneToOnedx {
public static void main(String[] args) {
Session session = HibernateUtils.getCurrentSession();
/*Transaction ts = null;
Carddx carddx = new Carddx();
carddx.setNumber("440882xxxxxxxxxxxxx");
Persondx persondx = new Persondx();
persondx.setName("Chester");
persondx.setCarddx(carddx);// 能过这个来绑定 人和身份证的关系
try {
ts = session.beginTransaction();
session.save(carddx);
session.save(persondx);
ts.commit();
} catch (Exception e) {
e.printStackTrace();
ts.rollback();// 回滚
} finally {
session.close();
}*/
// 查询可以能过Person 查到Card ，不是Cardi不能查到Person ，因为是单向关联，也是Person里有Card属性，Card里没有Person
/*Persondx p = (Persondx) session.load(Persondx.class, 15L);
System.out.println(p.getId()+":"+ p.getName());
// Hibernate: select person0_.id as id1_0_0_, person0_.name as name2_0_0_ from Persondx person0_ where person0_.id=?
// 15:Chester
Carddx c = p.getCarddx();
if(c != null) {
System.out.println(c.getId()+":"+c.getNumber());
// Hibernate: select card0_.id as id1_2_0_, card0_.number as number2_2_0_ from carddx card0_ where card0_.id=?
// 15:440882xxxxxxxxxxxxx
}
session.close();
*/
/*Persondx p = (Persondx) session.load(Persondx.class, 4L);
p.setId(3L);
Transaction ts = session.beginTransaction();
session.delete(p);
ts.commit();*/
}
}
就这个样子。。。下面是双向
双向关联：
Personsx.java
package com.ywj.TestHibernate.e;
import java.io.Serializable;
public class Personsx implements Serializable{
private static final long serialVersionUID = -3189538608590684635L;
private Long id;
private String name;
private Cardsx cardsx;// 他的身份证
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Cardsx getCardsx() {
return cardsx;
}
public void setCardsx(Cardsx cardsx) {
this.cardsx = cardsx;
}
}
Personsx.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.ywj.TestHibernate.e">
<class name="Personsx" table="Personsx" >
<id name="id" column="id">
<generator class="identity"></generator> <!-- 一个人的id是自增长的 -->
</id>
<property name="name" column="name" type="java.lang.String"/>
<one-to-one name="cardsx" class="Cardsx" cascade="all"></one-to-one>
</class>
</hibernate-mapping>
package com.ywj.TestHibernate.e;
import java.io.Serializable;
public class Cardsx implements Serializable {
private static final long serialVersionUID = -5428059743879860845L;
private Long id;
private String number;
private Personsx personsx;
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getNumber() {
return number;
}
public void setNumber(String number) {
this.number = number;
}
public Personsx getPersonsx() {
return personsx;
}
public void setPersonsx(Personsx personsx) {
this.personsx = personsx;
}
}
Cardsx.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.ywj.TestHibernate.e">
<class name="Cardsx" table="cardsx" >
<id name="id" column="id">
<generator class="foreign">
<param name="property">personsx</param> <!-- 一对一嘛 card的id就由person来决定-->
</generator>
</id>
<property name="number" column="number" type="java.lang.String"/>
<!-- 一对一设置 constrained="true" 进行约束操作 cardsx表id FK约束 参考表personsx.id-->
<one-to-one name="personsx" class="Personsx" constrained="true"></one-to-one>
</class>
</hibernate-mapping>测试demo:
TestOneToOnesx.java
package com.ywj.TestHibernate.test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.ywj.TestHibernate.e.Cardsx;
import com.ywj.TestHibernate.e.Personsx;
public class TestOneToOnesx {
public static void main(String[] args) {
Session session = HibernateUtils.getCurrentSession();
Transaction ts = null;
Cardsx cardsx = new Cardsx();
cardsx.setNumber("440882xxxxxxxxxxxxx");
Personsx personsx = new Personsx();
personsx.setName("Chester");
personsx.setCardsx(cardsx);// 能过这个来绑定 人和身份证的关系
cardsx.setPersonsx(personsx);
try {
ts = session.beginTransaction();
session.save(cardsx);
session.save(personsx);
ts.commit();
} catch (Exception e) {
e.printStackTrace();
ts.rollback();// 回滚
} finally {
session.close();
}
// 可以通过person来查询card
/*Personsx p = (Personsx) session.load(Personsx.class, 3L);
System.out.println(p.getId()+":"+ p.getName());
Cardsx c = p.getCardsx();
if(c != null) {
System.out.println(c.getId()+":"+c.getNumber());
}
System.out.println("xxxxxxxxxxxxxx");
// 也可以通过card来查询person
Cardsx cc = (Cardsx) session.load(Cardsx.class, 3L);
System.out.println(cc.getNumber()+cc.getId());
Personsx pp = cc.getPersonsx();
System.out.println(pp.getName()+pp.getId());
session.close();*/
}
}