08 - Value-Types-and-Embedding-Objects

How would you save an object in database e.g. list, array etc.

In hibernate we see two kind of objects - Entity object and value object

Entity object:  It has an object which is saved as a separate table in database and it is independent. It has value of its own

Value object: it is an object that has a data, but it does not have meaning as of itself it provide meaning to other object e.g. address. It doesn’t have value of its own.

@Embeddable -> Object must be embedded in some other object

@Embedded-> same as Embeddable but it will add at object initialization.

The @Embedded annotation is used to specify the Address entity should be stored in the USER_DETAILS table as a component. @Embeddable annotation is used to specify the Address class will be used as a component. The Address class cannot have a primary key of its own; it uses the enclosing class primary key.

HibernateTest.java

package org.yash.hibernate;

import java.util.Date;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

import org.yash.dto.Address;

import org.yash.dto.UserDetails;

public class HibernateTest {

      public static void main(String args[]){

            UserDetails user = new UserDetails();

            user.setUserName("First User");

            UserDetails user2 = new UserDetails();

            user2.setUserName("Second User");

           

            Address addr = new Address();

            addr.setCity("Bentonville");

            addr.setPincode("72712");

            addr.setState("Ar");

            addr.setStreet("2301 SE Saint Andrews");

           

            user.setAddress(addr);

            user.setJoinedDate(new Date());

            user.setDescription("Description of user goes here");

            user2.setAddress(addr);

            user2.setJoinedDate(new Date());

            user2.setDescription("Description of user goes here");     

           

            SessionFactory sessionFactory =

new Configuration().configure().buildSessionFactory();

           

            Session session = sessionFactory.openSession();

            /* It is used to save all the objects and to define single unit of work */

            session.beginTransaction();

           

            session.save(user);

            session.save(user2);

            session.getTransaction().commit();

           

            user = null;

           

            session = sessionFactory.openSession();

            session.beginTransaction();

            user = (UserDetails) session.get(UserDetails.class, 1);

            System.out.println("User name retrieved is "+user.getUserName());

      }

}

UserDetails.java

package org.yash.dto;

import java.util.Date;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

import javax.persistence.Table;

@Entity

@Table(name="USER_DETAILS")

public class UserDetails {

      /* @Id says "userId" is primary key */

      @Id @GeneratedValue (strategy=GenerationType.AUTO)

      private int userId;    

      private String userName;

      private Address address;

     

      private Date joinedDate;

      private String description;

     

      public int getUserId() {

            return userId;

      }

      public void setUserId(int userId) {

            this.userId = userId;

      }

      public String getUserName() {

            return userName;

      }

      public void setUserName(String userName) {

            this.userName = userName;

      }

      public Date getJoinedDate() {

            return joinedDate;

      }

      public void setJoinedDate(Date joinedDate) {

            this.joinedDate = joinedDate;

      }

      public String getDescription() {

            return description;

      }

      public void setDescription(String description) {

            this.description = description;

      }

      public void setAddress(Address address) {

            this.address = address;

      }

      public Address getAddress() {

            return address;

      }

}

Address.java

package org.yash.dto;

import javax.persistence.Embeddable;

@Embeddable

public class Address {

      private String street;

      private String city;

      private String state;

      private String pincode;

      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 getPincode() {

            return pincode;

      }

      public void setPincode(String pincode) {

            this.pincode = pincode;

      }

     

}

hibernate.cfg.xml

<?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">

            org.postgresql.Driver

        </property>

        <property name="connection.url">

            jdbc:postgresql://localhost:5433/hibernatedb

        </property>

        <property name="connection.username">postgres</property>

        <property name="connection.password">admin</property>

        <!-- JDBC connection pool (use the built-in) -->

        <property name="connection.pool_size">1</property>

        <!-- SQL dialect -->

        <property name="dialect">

            org.hibernate.dialect.PostgreSQLDialect

        </property>

        <!-- Enable Hibernate's automatic session context management -->

        <property name="current_session_context_class">thread</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> 

<!-- create / update -->

   

          <!-- Names the annotated entity class -->

          <mapping class="org.yash.dto.UserDetails"/>

    </session-factory>

</hibernate-configuration>