One to Many Mapping in Hibernate Example

Target:
Fields (including property get methods)Defines a many-valued association with one-to-many multiplicity. If the collection is defined using generics to specify the element type, the associated target entity type need not be specified; otherwise the target entity class must be specified. If the relationship is bidirectional, the mappedBy element must be used to specify the relationship field or property of the entity that is the owner of the relationship. The OneToMany annotation may be used within an embeddable class contained within an entity class to specify a relationship to a collection of entities. If the relationship is bidirectional, the mappedBy element must be used to specify the relationship field or property of the entity that is the owner of the relationship.

package com.sdnext.hibernate.tutorial.dto;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name=”VEHICLE”)
public class Vehicle
{
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name=”VEHICLE_ID”)
private int vehicleId;

  @Column(name=”VEHICLE_NAME”)
private String vehicleName;

public int getVehicleId() {
return vehicleId;
}
public void setVehicleId(int vehicleId) {
this.vehicleId = vehicleId;
}
public String getVehicleName() {
return vehicleName;
}
public void setVehicleName(String vehicleName) {
this.vehicleName = vehicleName;
}
}

package com.sdnext.hibernate.tutorial.dto;

import java.util.ArrayList;
import java.util.Collection;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.JoinTable;
import javax.persistence.OneToMany;
import javax.persistence.Table;

@Entity
@Table (name=”USER”)
public class UserDetails
{
@Id
@Column(name=”USER_ID”)
@GeneratedValue(strategy=GenerationType.AUTO)
private int    userId;

@Column(name=”USER_NAME”)
private String userName;

@OneToMany
    @JoinTable( name=”USER_VEHICLE”,
                joinColumns=@JoinColumn(name=”USER_ID”),
                inverseJoinColumns=@JoinColumn(name=”VEHICLE_ID”)) //its optional using for name configuration of the join table
private Collection<Vehicle> vehicle = new ArrayList<Vehicle>();

public int getUserId() {
return userId;
}
public Collection<Vehicle> getVehicle() {
return vehicle;
}
public void setVehicle(Collection<Vehicle> vehicle) {
this.vehicle = vehicle;
}
public void setUserId(int userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
}

<?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>
<!– Database connection settings –>
<property name=”connection.driver_class”>com.mysql.jdbc.Driver</property>
<property name=”connection.url”>jdbc:mysql://localhost:3306/hibernateDB</property>
<property name=”connection.username”>root</property>
<property name=”connection.password”>root</property>

<!– JDBC connection pool (use the built-in) –>
<property name=”connection.pool_size”>1</property>

<!– SQL dialect –>
<property name=”dialect”>org.hibernate.dialect.MySQLDialect</property>

<!– Enable Hibernate’s automatic session context management –>
<property name=”current_session_context_class”>thread</property>

<!– Disable the second-level cache –>
<property name=”cache.provider_class”>org.hibernate.cache.NoCacheProvider</property>

<!– Echo all executed SQL to stdout –>
<property name=”show_sql”>true</property>

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

<mapping class=”com.sdnext.hibernate.tutorial.dto.UserDetails”/>
<mapping class=”com.sdnext.hibernate.tutorial.dto.Vehicle”/>

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

UserDetails user = new UserDetails(); //create the user entity object

Vehicle vehicle = new Vehicle(); //create the first vehicle entity object
Vehicle vehicle2 = new Vehicle(); //create the second vehicle entity

vehicle.setVehicleName(“BMW Car”); //set the value to the vehicle entity
vehicle2.setVehicleName(“AUDI Car”);

user.setUserName(“Dinesh Rajput”); //Set the value to the user entity
user.getVehicle().add(vehicle); //add vehicle to the list of the vehicle
user.getVehicle().add(vehicle2);
      
        SessionFactory sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); //create session factory object
Session session = sessionFactory.openSession(); //create the session object
session.beginTransaction(); //start the transaction of the session object

session.save(vehicle); //saving the vehicle to the database
session.save(vehicle2);
session.save(user); //save the user to the database

session.getTransaction().commit(); //close the transaction
session.close(); //close the session
}
}
******************************************************************************
OUTPUT:
******************************************************************************
log4j:WARN No appenders could be found for logger (org.hibernate.cfg.annotations.Version).
log4j:WARN Please initialize the log4j system properly.
Hibernate: insert into VEHICLES (VEHICLE_NAME) values (?)
Hibernate: insert into VEHICLES (VEHICLE_NAME) values (?)
Hibernate: insert into USER (USER_NAME) values (?)
Hibernate: insert into USER_VEHICLE (USER_ID, VEHICLE_ID) values (?, ?)
Hibernate: insert into USER_VEHICLE (USER_ID, VEHICLE_ID) values (?, ?)