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;
}
}Hibernate corresponding mapping 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">
<hibernate-mapping package="cjq.hibernate.tutorial.domain">
<class name="Event" table="HI_EVENTS">
<id name="id" column="EVENT_ID">
<generator class="native"/>
</id>
<property name="date" type="timestamp" column="EVENT_DATE"/>
<property name="title"/>
<set name="participants" table="HI_PERSON_EVENT">
<key column="EVENT_ID"/>
<many-to-many column="PERSON_ID" class="PERSON"/>
</set>
</class>
</hibernate-mapping>Events associated with many to many people.
Person class:
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);
}
}Corresponding to hibernate Person.hbm.xml profile:
<?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">
<hibernate-mapping package="cjq.hibernate.tutorial.domain">
<class name="Person" table="HI_PERSON">
<id name="id" column="PERSON_ID">
<generator class="native"/>
</id>
<property name="age"/>
<property name="firstname"/>
<property name="lastname"/>
<set name="events" table="HI_EVENT">
<key column="PERSON_ID"/>
<many-to-many column="EVENT_ID" class="Event"/>
</set>
<set name="emailAddresses" table="HI_PERSON_EMAIL_ADDR">
<key column="PERSON_ID"/>
<element type="string" column="EMAIL_ADDR"/>
</set>
</class>
</hibernate-mapping>
Here, too, it reflects the relationship between people and events-many, while also adding an element of people's email addresses, with the collection represents, indicating a possible multiple email.
The following definition is necessary for two entities to operate.
First, create an Event instance and specific data stored in 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, the operation of 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 simply save the data, not associated.
Add association for the 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();
}
Adding human association, and human relations for the 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();
}In add an association for the event can be used to operate two separate 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");
}
Side note:
Get a list of entities as follows:
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;
}Description: "from Event" in the Event class name of an entity, rather than the name of the database table.
Reproduced in: https: //my.oschina.net/u/2552902/blog/543825