Hibernate - Using annotations based configuration



Hibrnate provides support for the annotations based mapping for the ORM(object relational mapping). You can use JPA annotations in hibernate to map the object to table. So , you don't require the *.hbm.xml file for the each entity to mapping in database. You can mix annotated persistent classes and classic hbm.cfg.xml declarations with the same SessionFactory.

You can however not declare a class several times (whether annotated or through hbm.xml). You cannot mix configuration strategies (hbm vs annotations) in an entity hierarchy either. Following annotaions are being used in the example;

@Entity declares the class as an entity (i.e. a persistent POJO class).
@Id declares the identifier property of this entity.
Other properties will be mapped by hibernate using convensions like column name, column type, table name etc.

Entity class
package domain;

import java.util.Date;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entity
public class Profile {
    private int id;
    private String name;
    private String email;
    private Date dateOfBirth;
    private long phone;

    public Profile() {

    }

    public Profile(int id, String name, String email, Date dateOfBirth,
            long phone) {
        super();
        this.id = id;
        this.name = name;
        this.email = email;
        this.dateOfBirth = dateOfBirth;
        this.phone = phone;
    }

    @Id
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getEmail() {
        return email;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Date getDateOfBirth() {
        return dateOfBirth;
    }

    public void setDateOfBirth(Date dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }

    public long getPhone() {
        return phone;
    }

    public void setPhone(long phone) {
        this.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">org.h2.Driver</property>
        <property name="connection.url">jdbc:h2:~/test;TRACE_LEVEL_FILE=3</property>
        <property name="connection.username">sa</property>
        <property name="connection.password" />
        <property name="connection.pool_size">1</property>
        <property name="dialect">org.hibernate.dialect.H2Dialect</property>
        <property name="current_session_context_class">thread</property>
        <property name="cache.provider_class">org.hibernate.cache.NoCacheProvider</property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto" >update</property>
        <mapping class="domain.Profile"/>
    </session-factory>
</hibernate-configuration>

--------------------------------------------------------------------------------------------------------------
import java.util.Calendar;
import org.hibernate.Session;
import org.hibernate.cfg.AnnotationConfiguration;

import domain.Profile;

public class Operations {
    public static void main(String[] args) {
        Session session = new AnnotationConfiguration().configure()
                .buildSessionFactory().openSession();
        session.beginTransaction();
        //create the date object to represent date, use calendar classs to do that
        Calendar date=Calendar.getInstance();
        date.set(19820220);
        Profile profile=new Profile(1,"hemraj","hemraj@domain.com",date.getTime(),983234923);
        session.save(profile);
        session.getTransaction().commit();
    }
}


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