首先是Event类，

 

public class Event {	 private int id;	    private String title;	    private Date date;	    private Set participants = new HashSet();	    	    public Event() {}	    public Date getDate() {	        return date;	    }	    public void setDate(Date date) {	        this.date = date;	    }	    public String getTitle() {	        return title;	    }	    public void setTitle(String title) {	        this.title = title;	    }		public int getId() {			return id;		}		public void setId(int id) {			this.id = id;		}		public Set getParticipants() {			return participants;		}		public void setParticipants(Set participants) {			this.participants = participants;		}}

其对应的hibernate映射文件为：Event.hbm.xml

事件与人有多对多的关联。

Person类为：

public class Person {	 	private int id;	    private int age;	    private String firstname;	    private String lastname;	    private Set events = new HashSet(); 	    	    private Set emailAddresses = new HashSet();		public int getAge() {			return age;		}		public void setAge(int age) {			this.age = age;		}		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 Set getEvents() {			return events;		}		public void setEvents(Set events) {			this.events = events;		}		public void setId(int id) {			this.id = id;		}		public int getId() {			return id;		}		public Set getEmailAddresses() {			return emailAddresses;		}		public void setEmailAddresses(Set emailAddresses) {			this.emailAddresses = emailAddresses;		}				@SuppressWarnings("unchecked")		public void addToEvnet(Event event){			this.getEvents().add(event);			event.getParticipants().add(this);		}				public void removeFromEvent(Event event){			this.getEvents().remove(event);			event.getParticipants().remove(this);		}}

其对应的hibernate配置文件Person.hbm.xml为：

这里，也体现出人与事件多对多的关系，同时，还加入的人的email地址的元素，用集合表示，说明有一个可能有多个email。

下面就要对定义的两个实体进行操作。

首先，创建一个Event实例，并将具体数据存入数据库：

private void createAndStoreEvent(String title, Date theDate){		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		session.beginTransaction();				Event event = new Event();		event.setDate(theDate);		event.setTitle(title);		session.save(event);						session.getTransaction().commit();				//HibernateUtil.getSessionFactory().close();			}

同样，对Person实例的操作：

private void createPerson(int age,String firstname,String lastname){		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		session.beginTransaction();				Person person = new Person();		person.setAge(age);		person.setFirstname(firstname);		person.setLastname(lastname);		session.save(person);				session.getTransaction().commit();	}

上面两个方法只是简单的保存数据，并未建立关联。

为事件添加关联：

private void addPersonToEvent(int personId,int eventId){		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		session.beginTransaction();				Person person = (Person)session.load(Person.class, personId);		Event event = (Event)session.load(Event.class, eventId);		person.getEvents().add(event);				session.getTransaction().commit();			}

为人添加关联，针对于人与email的关系：

private void addEmailToPerson(int personId,String emailAddress){		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		session.beginTransaction();				Person person = (Person)session.load(Person.class, personId);		person.getEmailAddresses().add(emailAddress);				session.getTransaction().commit();	}

在为事件添加关联，也可以使用两个不同的事务进行操作：

private void addPersonToEvent2(int personId,int eventId){		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		session.beginTransaction();				Person person = (Person)session.createQuery("select p from Person p left join fetch p.events where p.id=:pid").setParameter("pid", personId).uniqueResult();		Event event = (Event)session.load(Event.class, eventId);		session.getTransaction().commit();		//End of first unit of work;		person.getEvents().add(event);				//begin second unit of work;		Session session2 = HibernateUtil.getSessionFactory().getCurrentSession();		session2.beginTransaction();		session2.update(person);		session2.getTransaction().commit();		System.out.println("finish");			}

补充说明一下：

获取实体列表操作如下：

private List getEventList(String title, Date theDate){		Session session = HibernateUtil.getSessionFactory().getCurrentSession();		session.beginTransaction();						List list = session.createQuery("from Event").list();				session.getTransaction().commit();				return list;	}

说明："from Event"中Event为实体的类名，而不数据库的表名。