How to save collections into database using @ElementCollection, @JoinTable and @JoinColumn annotations in Hibernate Framework ?.

Program to demonstrate how to save collections into database using @ElementCollection, @JoinTable and @JoinColumn annotations in Hibernate Framework.

A simple POJO class (model) Customer.java

package com.hubberspot.hibernate.examples;

import java.util.HashSet;
import java.util.Set;
import javax.persistence.ElementCollection;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;

// @Entity to tell Hibernate that we need this Model
// class to get store in database as a table by name
// Customer
@Entity
public class Customer {

 // @Id to tell Hibernate that we need this Model
 // class having customerId as a Primary Key in the
 // table Customer created by @Entity
 @Id
 private int customerId;
 private String customerName;

 // In order to save collections into database
 // using Hibernate we use an annotation called as
 // @ElementCollection which creates a seperate table
 // for storing the contents of multiple addresses 
 // and associate a foreign key relationship with
 // Customer table.
 @ElementCollection

 // In order to provide user friendly name to the
 // separate table we use @JoinTable annotation which
 // takes in name as the name user wants to provide to 
 // collections table. We can also provide name to foreign key
 // using @JoinColumn annotation
 @JoinTable(name="Customer_Address" , joinColumns=@JoinColumn(name="Customer_Id"))
 private Set< Address >setOfAddresses = new HashSet< Address >();

 public Set< Address >getSetOfAddresses() {
  return setOfAddresses;
 }

 public void setSetOfAddresses(Set< Address >setOfAddresses) {
  this.setOfAddresses = setOfAddresses;
 }
 public int getCustomerId() {
  return customerId;
 }
 public void setCustomerId(int customerId) {
  this.customerId = customerId;
 }

 public String getCustomerName() {
  return customerName;
 }
 public void setCustomerName(String customerName) {
  this.customerName = customerName;
 }
}

A simple POJO class (model) Address which is being used as a collection into Customer

package com.hubberspot.hibernate.examples;

import javax.persistence.Embeddable;

// @Embeddable tells Hibernate that Address object 
// will be embedded into some other tables.
// The values of the properties will be populated
// into a table in which we want to embed the Address
@Embeddable
public class Address {

 private String street;
 private String city;
 private String state;
 private String zipCode;

 public String getStreet() {
  return street;
 }

 public void setStreet(String street) {
  this.street = street;
 }

 public String getCity() {
  return city;
 }

 public void setCity(String city) {
  this.city = city;
 }

 public String getState() {
  return state;
 }

 public void setState(String state) {
  this.state = state;
 }

 public String getZipCode() {
  return zipCode;
 }

 public void setZipCode(String zipCode) {
  this.zipCode = zipCode;
 } 

}

Hibernate Configuration XML file

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>
  <session-factory>
 <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
 <property name="connection.url">jdbc:mysql://localhost/customerdb</property>
 <property name="connection.username">root</property>
 <property name="connection.password">root</property>

 <!-- SQL dialect -->
 <property name="dialect">
  org.hibernate.dialect.MySQL5Dialect
 </property>

 <!-- Drop and re-create the database schema on startup  -->
 <property name="hbm2ddl.auto">create</property>

 <!-- Mapping class entry into configuration xml for annotated classes -->
 <mapping class="com.hubberspot.hibernate.examples.Customer" />

  </session-factory>
</hibernate-configuration>

A simple Test.java

package com.hubberspot.hibernate.examples;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class HibernateTest {
 public static void main(String[] args) {

  // Lets create a Customer Object 
  Customer customer = new Customer();
  customer.setCustomerId(1);
  customer.setCustomerName("Jonty");

  // Lets create multiple addresses object which will be
  // saved as a collections into a separate table
  Address address1 = new Address();
  address1.setStreet("Street Name 1");
  address1.setCity("City Name 1");
  address1.setState("State Name 1");
  address1.setZipCode("Zip-Code Value 1");

  Address address2 = new Address();
  address2.setStreet("Street Name 2");
  address2.setCity("City Name 2");
  address2.setState("State Name 2");
  address2.setZipCode("Zip-Code Value 2");

  customer.getSetOfAddresses().add(address1);
  customer.getSetOfAddresses().add(address2);

  // SessionFactory gives us a factory of sessions
  // Usually SessionFactory is been configured by the 
  // configuration file named as hibernate.cfg.xml
  // buildSessionFactory() builds the sessionFactory for us
  SessionFactory sessionFactory = new Configuration().
    configure().buildSessionFactory();

  // Session is created by calling openSession()
  // method on SessionFactory object
  Session session = sessionFactory.openSession();
  session.beginTransaction();

  // Our Transaction Code goes here 
  // i.e save, load , merge and remove
  // Lets save our Customer object created
  // above using sessions save method.
  session.save(customer);

  // Committing the transaction in order to save. 
  session.getTransaction().commit();
  // Closing the session
  session.close();
 }
}

Output of the program :

Two tables created into database as below: