Hibernate中联合主键映射学习

首先说下一个类中单个主键在hibernate中的映射配置

直接上代码：

<hibernate-mapping package="ray.po">
<class name="User" table="_user" lazy="true">
<id name="id">
<generator class="native"></generator>
</id>
<property name="name"></property>
<property name="age"></property>
</class>
</hibernate-mapping>

对应的实体类：

package ray.po;

public class User {
private int id;
private String name, age;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", age=" + age + "]";
}
public User(int id, String name, String age) {
super();
this.id = id;
this.name = name;
this.age = age;
}
public User() {
super();
}

}

测试代码：

package ray.po;

import org.hibernate.Session;

import ray.SessionUtil.HibernateSessionFactory;

public class UserTest {
public static void main(String[] args) {
User user = new User();
user.setName("雷盼");
user.setAge("26");
Session session = HibernateSessionFactory.getSession();
session.beginTransaction();
session.save(user);
session.getTransaction().commit();
session.close();
}
}

Hibernate: 
    create table _user (
        id integer not null auto_increment,
        name varchar(255),
        age varchar(255),
        primary key (id)
    )

但是有时候我们再设计数据库表的时候，会用多个字段作为联合主键，那么在hibernate中怎么配置这中情况呢？

配置文件：

<hibernate-mapping package="ray.compositeId">
<class name="Student" table="_Student" lazy="true">
<composite-id name="id" class="CompositeId">
<key-property name="firstName" column="_firstName"></key-property>
<key-property name="lastName" column="lastName"></key-property>
</composite-id>
<property name="age"></property>
</class>
</hibernate-mapping

实体类代码：

package ray.compositeId;

public class Student {
// 联合主键id
private CompositeId id;
private byte age;

public CompositeId getId() {
return id;
}

public void setId(CompositeId id) {
this.id = id;
}

public byte getAge() {
return age;
}

public void setAge(byte age) {
this.age = age;
}

}

联合主键的类：

package ray.compositeId;

import java.io.Serializable;

public class CompositeId implements Serializable {
private String firstName, 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;
}

}

测试代码：

package ray.compositeId;

import org.hibernate.Session;

import ray.SessionUtil.HibernateSessionFactory;
//测试联合主键
public class Test {
public static void main(String[] args) {
Student s = new Student();
CompositeId sid = new CompositeId();
sid.setFirstName("子诺");
sid.setLastName("雷");
s.setAge((byte) 12);
s.setId(sid);
Session session = HibernateSessionFactory.getSession();
session.beginTransaction();
session.save(s);
session.getTransaction().commit();
session.close();
}
}

Hibernate: 
    create table _Student (
        _firstName varchar(255) not null,
        lastName varchar(255) not null,
        age tinyint,
        primary key (_firstName, lastName)
    )