单向之一对多

举例：枪和子弹，一把枪有许多子弹

1、工具类：HibernateUtil

public class HibernateUtilEX {
private static Configuration configuration = null;
private static SessionFactory sessionFactory = null;
// 本地化线程、
private static ThreadLocal<Session> localSession = null;
static {
try {
// 加载Hibernate配置文件(默认加载bihernate.cfg.xml)
configuration = new Configuration().configure();
// 获取SessionFactory工厂对象
sessionFactory = configuration.buildSessionFactory();
localSession = new ThreadLocal<Session>();
} catch (Exception e) {
System.out.println("加载hibernate映射文件失败");
e.printStackTrace();
}
}
/**
* 得到Session对象
*
* @return Session
*/
public static Session openSession() throws HibernateException {
// 底层有一个Map<k,V>,K:线程ID，V:session ,一个线程绑定一个session
Session session = localSession.get();
if (session == null) {
session = sessionFactory.openSession();
localSession.set(session);
}
return session;
}
/**
* 关闭Session
*
* @throws HibernateException
*/
public static void closeSession() throws HibernateException {
Session session = localSession.get();
if (session != null) {
session.close();
}
localSession.set(null);
}
}

2、手枪实体类：GunEntity

public class GunEntity {
private int id;
private String type;
private Set<BulletEntity> bullets;
//子弹集合引用；
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
public Set<BulletEntity> getBullets() {
return bullets;
}
public void setBullets(Set<BulletEntity> bullets) {
this.bullets = bullets;
}
@Override
public String toString() {
return "GunEntity [id=" + id + ", type=" + type + ", bullets=" + bullets + "]";
}
}

配置文件：GunEntity.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zh.entity">
<class name="GunEntity" table="t_gun">
<!-- 映射标识属性(属性) -->
<id name="id" column="id" type="int">
<!-- 主键生成策略(自增主键) -->
<generator class="native" />
</id>
<!-- 映射普通属性 -->
<property name="type" column="type"></property>
<!-- 单向一对多 -->
<set name="bullets">
<!-- 指定外键 -->
<key column="gun_id"></key>
<!-- 映射关联类 -->
<one-to-many class="BulletEntity" />
</set>
</class>
</hibernate-mapping>

子弹实体类：BulletEntity

public class BulletEntity {
private int id;
private double caliber; //口径
private double weight;
//重量
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public double getCaliber() {
return caliber;
}
public void setCaliber(double caliber) {
this.caliber = caliber;
}
public double getWeight() {
return weight;
}
public void setWeight(double weight) {
this.weight = weight;
}
@Override
public String toString() {
return "BulletEntity [id=" + id + ", caliber=" + caliber + ", weight=" + weight + "]";
}
}

配置文件：BulletEntity.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.zh.entity">
<class name="BulletEntity" table="t_bullet">
<!-- 映射标识属性(属性) -->
<id name="id" column="id" type="int">
<!-- 主键生成策略(自增主键) -->
<generator class="native" />
</id>
<!-- 映射普通属性 -->
<property name="caliber" column="caliber"></property>
<property name="weight" column="weight"></property>
</class>
</hibernate-mapping>

3、在总配置文件hibernate.cfg.xml里添加配置映射文件

4、创建测试类：HibernateTest

public class HibernateTest2 {
public static void main(String[] args) {
HibernateTest test=new HibernateTest();
test.singleOneToMany();
}
//单向一对多测试
public void singleOneToMany() {
//开启会话
Session session=HibernatUtil.getSession();
//打开事物
Transaction transaction=session.beginTransaction();
/**
* 实例化手枪类
*/
GunEntity gunEntity = new GunEntity();
gunEntity.setType("手枪");
/**
* 实例化子弹类1
*/
BulletEntity bullet=new BulletEntity();
bullet.setCaliber(0.5);
bullet.setWeight(2.0);
session.persist(bullet);
/**
* 实例化子弹类2
*/
BulletEntity bullet2=new BulletEntity();
bullet2.setCaliber(0.3);
bullet2.setWeight(1.8);
session.persist(bullet2);
/**
* 将枪与子弹相关联
*/
Set<BulletEntity> bullets=new HashSet<>();
gunEntity.setBullets(bullets);
gunEntity.getBullets().add(bullet);
gunEntity.getBullets().add(bullet2);
//保存到数据库
session.persist(gunEntity);
//提交事物
transaction.commit();
//关闭会话
HibernatUtil.closeSession(session);
}
}

点击运行，测试成功！

看看数据库自动生成的数据：

最后

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