Java Tutorial/Hibernate/Many to Many Mapping

Many to Many Mapping

File: Main.java

   <source lang="java">

import java.util.List; import org.hibernate.Query; import org.hibernate.Session; public class Main {

 public static void main(String[] args) throws Exception {
   HibernateUtil hibernateUtil = new HibernateUtil();
   hibernateUtil.executeSQLCommand("create table event(event_id int,event_date date, title varchar)");
   hibernateUtil.executeSQLCommand("create table person(person_id int,firstname varchar, lastname varchar,age int)");
   hibernateUtil.executeSQLCommand("create table PERSON_EVENT(event_id int, person_id int)");
   Session session = hibernateUtil.getSession();
   
   Event event1 = new Event();
   event1.setTitle("event1");
   Event event2 = new Event();
   event2.setTitle("event2");
   
   Person person1 = new Person();
   person1.setFirstname("person1");
   Person person2 = new Person();
   person2.setFirstname("person2");
   
   person1.getEvents().add(event1);
   person1.getEvents().add(event2);
   
   person2.getEvents().add(event1);
   person2.getEvents().add(event2);
   
   session.save(event1);
   session.save(event2);
   
   session.save(person1);
   session.flush();
   
   person1.getEvents().clear();
   
   session.save(person1);
   session.flush();
   
   session.close();
   hibernateUtil.checkData("select * from event");
   hibernateUtil.checkData("select * from person");
   hibernateUtil.checkData("select * from PERSON_EVENT");
 }

}</source>

Many To Many Mapping Cascade Delete

File: Main.java

   <source lang="java">

import java.util.List; import org.hibernate.Query; import org.hibernate.Session; public class Main {

 public static void main(String[] args) throws Exception {
   HibernateUtil hibernateUtil = new HibernateUtil();
   hibernateUtil.executeSQLCommand("create table event(event_id int,event_date date, title varchar)");
   hibernateUtil.executeSQLCommand("create table person(person_id int,firstname varchar, lastname varchar,age int)");
   hibernateUtil.executeSQLCommand("create table PERSON_EVENT(event_id int, person_id int)");
   Session session = hibernateUtil.getSession();
   
   Event event1 = new Event();
   event1.setTitle("event1");
   Event event2 = new Event();
   event2.setTitle("event2");
   
   Person person1 = new Person();
   person1.setFirstname("person1");
   Person person2 = new Person();
   person2.setFirstname("person2");
   
   person1.getEvents().add(event1);
   person1.getEvents().add(event2);
   
   person2.getEvents().add(event1);
   person2.getEvents().add(event2);
   
   session.save(event1);
   session.save(event2);
   
   session.save(person1);
   session.flush();
   
   person1.getEvents().clear();
   
   session.save(person1);
   session.flush();
   
   session.close();
   hibernateUtil.checkData("select * from event");
   hibernateUtil.checkData("select * from person");
   hibernateUtil.checkData("select * from PERSON_EVENT");
 }

}</source>

Many To Many Mapping: set collection

File: Main.java

   <source lang="java">

import java.util.List; import org.hibernate.Query; import org.hibernate.Session; public class Main {

 public static void main(String[] args) throws Exception {
   HibernateUtil hibernateUtil = new HibernateUtil();
   hibernateUtil.executeSQLCommand("create table event(event_id int,event_date date, title varchar)");
   hibernateUtil.executeSQLCommand("create table person(person_id int,firstname varchar, lastname varchar,age int)");
   hibernateUtil.executeSQLCommand("create table PERSON_EVENT(event_id int, person_id int)");
   Session session = hibernateUtil.getSession();
   
   Event event1 = new Event();
   event1.setTitle("event1");
   Event event2 = new Event();
   event2.setTitle("event2");
   
   Person person1 = new Person();
   person1.setFirstname("person1");
   Person person2 = new Person();
   person2.setFirstname("person2");
   
   person1.getEvents().add(event1);
   person1.getEvents().add(event2);
   
   person2.getEvents().add(event1);
   person2.getEvents().add(event2);
   
   session.save(event1);
   session.save(event2);
   
   session.save(person1);
   session.flush();
   session.close();
   hibernateUtil.checkData("select * from event");
   hibernateUtil.checkData("select * from person");
   hibernateUtil.checkData("select * from PERSON_EVENT");
 }

}</source>