Save object and link ing

The first is the event class,

 

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;}}

The corresponding hibernate ing file is event. HBM. xml.

<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
There are many-to-many associations between events and people.
The person class is:
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);}}
The corresponding hibernate configuration file person. HBM. XML is:
<?xml version="1.0"?><!DOCTYPE hibernate-mapping PUBLIC        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
Here, it also shows the many-to-many relationship between people and events. At the same time, the e-mail address element of the added person is represented by a set, indicating that there may be multiple emails.
The following operations are performed on the two defined entities.
First, create an event instance and save the specific data to the database:
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();}
Similarly, operations on the person instance:
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();}
The above two methods only save data and do not establish association.
Add an association for an event:
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();}
Add associations for people, targeting the relationship between people and email:
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();}
When adding an association for an event, you can also perform operations using two different transactions:
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");}
Additional instructions:
To obtain the Object List, perform the following operations:
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;}
Note: In "from event", event is the class name of the object, instead of the Table Name of the database.