In this tutorial you will learn how to map many-to-many relationship using Hibernate. Consider the following relationship between Vehicle and UserDetails entity.
UserDetail.java
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.ManyToMany; 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; @ManyToMany 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; } }
Vehicle.java
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.ManyToMany; 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; @ManyToMany(mappedBy="vehicle") private Collection<UserDetails> user = new ArrayList<UserDetails>(); public Collection<UserDetails> getUser() { return user; } public void setUser(Collection<UserDetails> user) { this.user = user; } 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; } }
hibernate.cfg.xml:
<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"> </mapping></mapping></session-factory> </hibernate-configuration>
HibernateTestDemo.java
package com.sdnext.hibernate.tutorial; import org.hibernate.Session; import org.hibernate.SessionFactory; import org.hibernate.cfg.AnnotationConfiguration; import com.sdnext.hibernate.tutorial.dto.UserDetails; import com.sdnext.hibernate.tutorial.dto.Vehicle; public class HibernateTestDemo { /** * @param args */ public static void main(String[] args) { UserDetails user = new UserDetails(); UserDetails user2 = new UserDetails(); Vehicle vehicle = new Vehicle(); Vehicle vehicle2 = new Vehicle(); vehicle.setVehicleName("Car"); vehicle.getUser().add(user); vehicle.getUser().add(user2); vehicle2.setVehicleName("Jeep"); vehicle2.getUser().add(user2); vehicle2.getUser().add(user); user.setUserName("First User"); user2.setUserName("Second User"); user.getVehicle().add(vehicle); user.getVehicle().add(vehicle2); user2.getVehicle().add(vehicle); user2.getVehicle().add(vehicle2); SessionFactory sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); Session session = sessionFactory.openSession(); session.beginTransaction(); session.save(vehicle); session.save(vehicle2); session.save(user); session.save(user2); session.getTransaction().commit(); session.close(); } }
Using Mapping files instead of Annotation
userDetail.hbm.xml
<hibernate-mapping> <class name="com.sdnext.hibernate.tutorial.dto.UserDetails" table="USER"> <id column="ID" name="userId" type="long"> <generator class="assigned"> </generator></id> <property column="column" name="UserName"> <list cascade="all" name="vehicle" table="USER_VEHICLE"> <key column="USER_ID"> <many-to-many class="com.sdnext.hibernate.tutorial.dto.Vehicle" column="VEHICLE_ID"> </many-to-many></key></list> </property></class> </hibernate-mapping>
vehicle.hbm.xml
<hibernate-mapping> <class name="com.sdnext.hibernate.tutorial.dto.Vehicle" table="VEHICLE"> <id column="ID" name="userId" type="long"> <generator class="assigned"> </generator></id> <property column="VEHICLE_NAME" name="vehicleName"> </property></class> </hibernate-mapping>
View Comments
can you plz tell the table structure of manytomany mapping
Hi Heena,
Please go to the following link and you can check table structure as well.
https://www.dineshonjava.com/spring-crud-example-using-many-to-one/
https://www.dineshonjava.com/spring-crud-example-using-one-to-one/