Hibernate实战——基于复合主键的关联关系
一 配置文件
com.mysql.jdbc.Driver
jdbc:mysql://localhost/hibernate
root
32147
20
1
5000
100
3000
2
true
org.hibernate.dialect.MySQL5InnoDBDialect
update
true
true
二 PO
Person
package org.crazyit.app.domain;
import java.util.*;
import javax.persistence.*;
@Entity
@Table(name="person_inf")
public class Person
implements java.io.Serializable
{
// 定义first成员变量，作为标识属性的成员
@Id
private String first;
// 定义last成员变量，作为标识属性的成员
@Id
private String last;
private int age;
// 记录该Person实体关联的所有Address实体
@OneToMany(targetEntity=Address.class, mappedBy="person"
, cascade=CascadeType.ALL)
private Set addresses
= new HashSet<>();
// first的setter和getter方法
public void setFirst(String first)
{
this.first = first;
}
public String getFirst()
{
return this.first;
}
// last的setter和getter方法
public void setLast(String last)
{
this.last = last;
}
public String getLast()
{
return this.last;
}
// age的setter和getter方法
public void setAge(int age)
{
this.age = age;
}
public int getAge()
{
return this.age;
}
// addresses的setter和getter方法
public void setAddresses(Set addresses)
{
this.addresses = addresses;
}
public Set getAddresses()
{
return this.addresses;
}
// 重写equals()方法，根据first、last进行判断
public boolean equals(Object obj)
{
if (this == obj)
{
return true;
}
if (obj != null && obj.getClass() == Person.class)
{
Person target = (Person)obj;
return target.getFirst().equals(this.first)
&& target.getLast().equals(this.last);
}
return false;
}
// 重写hashCode()方法，根据first、last计算hashCode值
public int hashCode()
{
return getFirst().hashCode() * 31
+ getLast().hashCode();
}
}Address
package org.crazyit.app.domain;
import javax.persistence.*;
@Entity
@Table(name="address_inf")
public class Address
{
// 标识属性
@Id @Column(name="address_id")
@GeneratedValue(strategy=GenerationType.IDENTITY)
private int addressId;
// 定义代表地址详细信息的成员变量
private String addressDetail;
// 记录该Address实体关联的Person实体
@ManyToOne(targetEntity=Person.class)
// 使用@JoinColumns包含多个@JoinColumn定义外键列
@JoinColumns({
// 由于主表使用了复合主键（有多个主键列）
// 因此需要使用多个@JoinColumn定义外键列来参照person_inf表的多个主键列
@JoinColumn(name="person_first"
, referencedColumnName="first" , nullable=false),
@JoinColumn(name="person_last"
, referencedColumnName="last" , nullable=false)
})
private Person person;
// 无参数的构造器
public Address()
{
}
// 初始化全部成员变量的构造器
public Address(String addressDetail)
{
this.addressDetail = addressDetail;
}
// addressId的setter和getter方法
public void setAddressId(int addressId)
{
this.addressId = addressId;
}
public int getAddressId()
{
return this.addressId;
}
// addressDetail的setter和getter方法
public void setAddressDetail(String addressDetail)
{
this.addressDetail = addressDetail;
}
public String getAddressDetail()
{
return this.addressDetail;
}
// person的setter和getter方法
public void setPerson(Person person)
{
this.person = person;
}
public Person getPerson()
{
return this.person;
}
}三 测试
1 工具类
package lee;
import org.hibernate.*;
import org.hibernate.cfg.*;
import org.hibernate.service.*;
import org.hibernate.boot.registry.*;
public class HibernateUtil
{
public static final SessionFactory sessionFactory;
static
{
try
{
// 使用默认的hibernate.cfg.xml配置文件创建Configuration实例
Configuration cfg = new Configuration()
.configure();
// 以Configuration实例来创建SessionFactory实例
ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder()
.applySettings(cfg.getProperties()).build();
sessionFactory = cfg.buildSessionFactory(serviceRegistry);
}
catch (Throwable ex)
{
System.err.println("Initial SessionFactory creation failed." + ex);
throw new ExceptionInInitializerError(ex);
}
}
// ThreadLocal可以隔离多个线程的数据共享，因此不再需要对线程同步
public static final ThreadLocal session
= new ThreadLocal();
public static Session currentSession()
throws HibernateException
{
Session s = session.get();
// 如果该线程还没有Session,则创建一个新的Session
if (s == null)
{
s = sessionFactory.openSession();
// 将获得的Session变量存储在ThreadLocal变量session里
session.set(s);
}
return s;
}
public static void closeSession()
throws HibernateException
{
Session s = session.get();
if (s != null)
s.close();
session.set(null);
}
} 2 测试类
package lee;
import org.hibernate.Transaction;
import org.hibernate.Session;
import java.util.*;
import org.crazyit.app.domain.*;
public class PersonManager
{
public static void main(String[] args)
{
PersonManager mgr = new PersonManager();
mgr.createAndStorePerson();
HibernateUtil.sessionFactory.close();
}
private void createAndStorePerson()
{
Session session = HibernateUtil.currentSession();
Transaction tx = session.beginTransaction();
// 创建Person对象
Person person = new Person();
person.setAge(29);
// 为复合主键的两个成员设置值
person.setFirst("crazyit.org");
person.setLast("疯狂Java联盟");
Address a1 = new Address("广州天河");
a1.setPerson(person);
Address a2 = new Address("上海虹口");
a2.setPerson(person);
// 先保存主表实体
session.save(person);
// 再保存从表实体
session.save(a1);
session.save(a2);
tx.commit();
HibernateUtil.closeSession();
}
}四 测试
Hibernate:
insert
into
person_inf
(age, last, first)
values
(?, ?, ?)
Hibernate:
insert
into
address_inf
(addressDetail, person_last, person_first)
values
(?, ?, ?)
Hibernate:
insert
into
address_inf
(addressDetail, person_last, person_first)
values
(?, ?, ?)
