Value Types and Embedding Objects in Hibernate

“An object of value type has no database identity; it belongs to an entity instance and its persistent state is embedded in the table row of the owning entity. Value types don’t have identifiers or identifier properties”

@Entity
@Table(name=”USER_TABLE”)

     @Id @GeneratedValue(strategy=GenerationType.AUTO)
     @Column(name=”USER_ID”, type=”INTEGER”)
      private long userId;
      @Column(name=”USER_NAME”, type=”String”)
       private String userName;
      @Column(name=USER_ADDRESS, type=”String”)
       private String address;
      @Column(name=”USER_PHONE”, type=”INTEGER”)
       private long phone;
      @Column(name=”DOB”, type=”TIMESTAMP”)
       private Date dob;

In Above table we saw that type of the all fields of the class USER CLASS have database entity type object. 

here USER CLASS have a field Address type of the Value type object means in the database there are no meaning of Address type object.

Address type object have the four other fields like.

1. Street

2. City

3. State

This scenario is working in the hibernate only one condition is Address Object should be a Value Object (means there is no meaning to itself its provide the meaning to the entity object).

In this approach there are some problems are

1. Table complexity

2. Data Redundancy

3. User may have multiple Address like home address and office address etc.

Look the above example in the code…
Address.java

package com.sdnext.hibernate.tutorial.dto;

import java.util.Date;

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

@Entity
@Table (name=”USER_TABLE”)
public class UserDetails
{
    @Id @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name=”USER_ID”)
    private int    userId;
   
    @Column(name=”USER_NAME”)
    private String userName;
   
    @Embedded //For value type object
    private Address address;
   
    @Column(name=”USER_PHONE”)
    private String phone;
   
    @Column(name=”DOB”)
    private Date dob;
   
    public void setUserId(int userId) {
        this.userId = userId;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public Address getAddress() {
        return address;
    }
    public void setAddress(Address address) {
        this.address = address;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone = phone;
    }
    public Date getDob() {
        return dob;
    }
    public void setDob(Date dob) {
        this.dob = dob;
    }
    public int getUserId() {
        return userId;
    }
    public String toString()
    {
        return “[User Name: “+userName+”User Id: “+userId+” User Address “+address+” Use phone ” +phone+” ]”;
    }
}

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

package com.sdnext.hibernate.tutorial;

import java.util.Date;

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

import com.sdnext.hibernate.tutorial.dto.Address;
import com.sdnext.hibernate.tutorial.dto.UserDetails;

public class HibernateTestDemo {
    /**
     * @param args
     */
    public static void main(String[] args)
    {
        UserDetails user1 = new UserDetails(); //create first user
        UserDetails user2 = new UserDetails(); //create second user
             
        user1.setUserName(“Dinesh Rajput”);
        user2.setUserName(“Anamika Rajput”);
       
        Address address1 = new Address(); //create first value type object for  entity type object user1
        address1.setStreet(“K Block House No. 403”);
        address1.setCity(“Mangol Puri”);
        address1.setState(“New Delhi”);
        address1.setPincode(“110083”);
        user1.setAddress(address1);
       
        Address address2 = new Address();//create second value type object for  entity type object user2
        address2.setStreet(“Film City”);
        address2.setCity(“Noida”);
        address2.setState(“UP”);
        address2.setPincode(“201301”);
        user2.setAddress(address2);
       
        user1.setDob(new Date());
        user1.setPhone(“+91-9953423462”);
       
        user2.setDob(new Date());
        user2.setPhone(“+91-9973423462”);
       
        SessionFactory sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); //create a session factory object
        Session session = sessionFactory.openSession(); // create session object from session factory
        session.beginTransaction(); //begin transaction for this session
       
        session.save(user1); //save the first user
        session.save(user2); //save the second user
       
        session.getTransaction().commit(); //commit the transaction the session
        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 USER_TABLE (CITY_NAME, PIN_CODE, STATE_NAME, STREET_NAME, DOB, USER_PHONE, USER_NAME) values (?, ?, ?, ?, ?, ?, ?)
Hibernate: insert into USER_TABLE (CITY_NAME, PIN_CODE, STATE_NAME, STREET_NAME, DOB, USER_PHONE, USER_NAME) values (?, ?, ?, ?, ?, ?, ?)

Here we have seen that an Entity Type Object USER has a Value Type Object(or Embeddable Object ) ADDRESS with corresponding fields name street, city, pin-code and state save to the database table USER_TABLE with value type object’s column name (CITY_NAME, PIN_CODE, STATE_NAME, STREET_NAME).

package com.sdnext.hibernate.tutorial.dto;

import java.util.Date;

import javax.persistence.AttributeOverride;
import javax.persistence.AttributeOverrides;
import javax.persistence.Column;
import javax.persistence.Embedded;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;

@Entity
@Table (name=”USER_TABLE”)public class UserDetails
{
    @Id
    @Column(name=”USER_ID”)
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int    userId;
   
    @Column(name=”USER_NAME”)
    private String userName;
   
    @Column(name=”DOB”)
    private Date joinDate;
   
    @Column(name=”ADDRESS”)
    @Embedded
    @AttributeOverrides({
    @AttributeOverride(name=”street”, column=@Column(name=”HOME_STREET_NAME”)),
    @AttributeOverride(name=”city”, column=@Column(name=”HOME_CITY_NAME”)),
    @AttributeOverride(name=”state”, column=@Column(name=”HOME_STATE_NAME”)),
    @AttributeOverride(name=”pincode”, column=@Column(name=”HOME_PIN_CODE”))})
    private Address homeAddress;
   
    @Embedded
    private Address permanentAddress;
   
    @Column(name=”Phone”)
      private String phone;
   
    public int getUserId() {
        return userId;
    }
    public Address getHomeAddress() {
        return homeAddress;
    }
    public void setHomeAddress(Address homeAddress) {
        this.homeAddress = homeAddress;
    }
    public void setUserId(int userId) {
        this.userId = userId;
    }
    public String getUserName() {
        return userName;
    }
    public void setUserName(String userName) {
        this.userName = userName;
    }
    public Date getDob() {
        return dob;
    }
    public void setDob(Date dob) {
        this.dob= dob;
    }
    public Address getPermanentAddress() {
        return permanentAaddress;
    }
    public void setPermanentAddress(Address permanentAddress) {
        this.permanentAddress = permanentAddress;
    }
    public String getPhone() {
        return phone;
    }
    public void setPhone(String phone) {
        this.phone= phone;
    }
   
    public String toString()
    {
        return “[User Name: “+userName+”n Permanent Address: “+permanentAddress+”n Home Address: “+homeAddress+”n Date of Birth: “+dob+”n Phone: “+phone+”]”;
    }
}

package com.sdnext.hibernate.tutorial;

import java.util.Date;

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

import com.sdnext.hibernate.tutorial.dto.Address;
import com.sdnext.hibernate.tutorial.dto.UserDetails;

public class HibernateTestDemo {

    /**
     * @param args
     */
    public static void main(String[] args)
    {
        UserDetails user = new UserDetails(); //create an user is entity type object
        //user.setUserId(1);
        user.setUserName(“Dinesh Rajput”);
       
        Address address = new Address(); //create an value type object of address class for home address
        address.setStreet(“Block House No”);
        address.setCity(“MangolaPuri”);
        address.setState(“New Delhi”);
        address.setPincode(“110089”);
        user.setHomeAddress(address); //set the home address
       
        Address address1 = new Address();//create another value type object for the permanent address
        address1.setStreet(“Film City”);
        address1.setCity(“Noida”);
        address1.setState(“UP”);
        address1.setPincode(“201301”);
        user.setPermanentAddress(address1);//set the permanent address
       
        user.setDob(new Date());
        user.setPhone(“9999222211”);
       
        SessionFactory sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); //create a session factory object
        Session session = sessionFactory.openSession(); //create a session object
        session.beginTransaction(); //transaction object start
        session.save(user); //  save the entity type object user to the database
        session.getTransaction().commit(); //commit the transaction object
        session.close(); //close the session
        }
}