Hibernate映射联合主键

数据库建表语句为：

CREATE TABLE `T_PERSON` (
  `firstname` VARCHAR(10) NOT NULL,
  `lastname` VARCHAR(10) NOT NULL,
  `address` VARCHAR(20),
  `phone` int(10) unsigned,
  PRIMARY KEY (`firstname`,`lastname`)
) ENGINE=InnoDB DEFAULT CHARSET=gb2312;

方式一：基于实体类属性

对于实体的PO类，有2个要求：

1，必须继承Serializable接口

2，必须重写equals()方法和hashcode()方法（个人认为不是必须重写，只要其默认hascode能唯一的确定任何一个Person类即可，当然使用联合主键字段firstname和lastname重写equals()方法和hashcode()方法后，即可通过firstname和lastname唯一确定一个Person类，更符合数据库中firstname和lastname做为联合主键的设计）

public class Person implements Serializable{
	private static final long serialVersionUID = 1L;
	private String firstname;
	private String lastname;
	private String address;
	private Integer phone;
	
	public Person(){}
	
	public String getFirstname() {
		return firstname;
	}
	public void setFirstname(String firstname) {
		this.firstname = firstname;
	}
	public String getLastname() {
		return lastname;
	}
	public void setLastname(String lastname) {
		this.lastname = lastname;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	public Integer getPhone() {
		return phone;
	}
	public void setPhone(Integer phone) {
		this.phone = phone;
	}
	
	public int hashCode() {
		return getFirstname().hashCode()*11 + 
				getLastname().hashCode();
	}
	
	public boolean equals(Object obj) {
		if(null == obj){
			return false;
		}
		if(this == obj){
			return true;
		}
		if(obj.getClass() == Person.class){
			Person p = (Person)obj;
			if(p.getFirstname().equals(getFirstname()) &&
					p.getLastname().equals(getLastname())){
				return true;
			}
		}
		return false;
	}
}

PO类配置文件Person.hbm.xml：

<?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="com.po.Person" table="T_PERSON">
    	<composite-id>
    		<key-property name="firstname" column="firstname" type="string"/>
    		<key-property name="lastname" column="lastname" type="string"/>
    	</composite-id>
        <property name="address" column="address" type="string"/>
        <property name="phone" column="phone" type="integer"/>
    </class>
</hibernate-mapping>

Hibernate配置文件hibernate.cfg.xml：

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
		"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
	<session-factory>
		<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
		<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
		<property name="connection.url">jdbc:mysql://localhost:3306/mydb</property>
		<property name="connection.username">root</property>
		<property name="connection.password">196428</property>
		
		<property name="hibernate.jdbc.batch_size">50</property>
		
		<mapping resource="com/po/Person.hbm.xml" />
	</session-factory>
</hibernate-configuration>

测试类：

public class Test {
	public static void main(String[] args) {
		Configuration conf = new Configuration();
		SessionFactory sessionFactory = conf.configure().buildSessionFactory();
		Session session = sessionFactory.openSession();
		Transaction tr = session.beginTransaction();
		
		Person p1 = new Person();
		p1.setFirstname("sean");
		p1.setLastname("zou");
		p1.setAddress("address");
		p1.setPhone(123);
		session.save(p1);
		System.out.println("save successfully!");
		
		Person p2 = new Person();
		p2.setFirstname("sean");
		p2.setLastname("zou");
		p2 = (Person)session.get(Person.class,p2);
		p2.setFirstname("angel");
		p2.setLastname("baby");
		p2.setAddress("address2");
		p2.setPhone(123);
		session.merge(p2);
		System.out.println("merge successfully!");
			
		tr.commit();
		session.close();
	}
}

运行结果为：

save successfully!
merge successfully!

最终数据库里只有一条数据：

firstname	lastname	address	phone
angel	baby	address2	123

方式二：基于主键类

public class PersonPK implements Serializable{
	private static final long serialVersionUID = 1L;
	private String firstname;
	private String lastname;
	
	public String getFirstname() {
		return firstname;
	}
	public void setFirstname(String firstname) {
		this.firstname = firstname;
	}
	public String getLastname() {
		return lastname;
	}
	public void setLastname(String lastname) {
		this.lastname = lastname;
	}
	
	public int hashCode() {
		return getFirstname().hashCode()*11 + 
				getLastname().hashCode();
	}
	
	public boolean equals(Object obj) {
		if(null == obj){
			return false;
		}
		if(this == obj){
			return true;
		}
		if(obj.getClass() == PersonPK.class){
			PersonPK pk = (PersonPK)obj;
			if(pk.getFirstname().equals(getFirstname()) &&
					pk.getLastname().equals(getLastname())){
				return true;
			}
		}
		return false;
	}
}

public class Person implements Serializable{
	private static final long serialVersionUID = 1L;
	private PersonPK personPK;
	private String address;
	private Integer phone;
	
	public Person(){}
	
	public PersonPK getPersonPK() {
		return personPK;
	}
	public void setPersonPK(PersonPK personPK) {
		this.personPK = personPK;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
	public Integer getPhone() {
		return phone;
	}
	public void setPhone(Integer phone) {
		this.phone = phone;
	}
}

<?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="com.po.Person" table="T_PERSON">
    	<composite-id name="personPK" class="com.po.PersonPK">
    		<key-property name="firstname" column="firstname" type="string"/>
    		<key-property name="lastname" column="lastname" type="string"/>
    	</composite-id>
        <property name="address" column="address" type="string"/>
        <property name="phone" column="phone" type="integer"/>
    </class>
</hibernate-mapping>

public class Test {
	public static void main(String[] args) {
		Configuration conf = new Configuration();
		SessionFactory sessionFactory = conf.configure().buildSessionFactory();
		Session session = sessionFactory.openSession();
		Transaction tr = session.beginTransaction();
		
		PersonPK pk = new PersonPK();
		pk.setFirstname("sean");
		pk.setLastname("zou");
		
		Person p1 = new Person();
		p1.setPersonPK(pk);
		p1.setAddress("address");
		p1.setPhone(123);
		session.save(p1);
		System.out.println("save successfully!");
		
		Person p2 = (Person)session.get(Person.class,pk);
		p2.setAddress("address2");
		p2.setPhone(123);
		session.merge(p2);
		System.out.println("merge successfully!");
			
		tr.commit();
		session.close();
	}
}

运行结果为：

save successfully!
merge successfully!

最终数据库里只有一条数据：

firstname	lastname	address	phone
sean	zou	address2	123