API or code : Difference between Hibernate 3 and 4?

Question

I have pasted Hibernate 3 configuration file , SessionFactory class to configure this config.xml and a bean with JPA annotations. I want to know if I were using Hibernate 4 then what would have been the changes in the context at code level or very broad differences or advancements in layman language.

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="hibernate.connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
        <property name="hibernate.connection.url">jdbc:oracle:thin:@192.168.2.144:1521:xe</property>
        <property name="hibernate.connection.username">prateek</property>
        <property name="connection.password">prateek</property>
        <property name="connection.pool_size">1</property>
        <property name="hibernate.dialect">org.hibernate.dialect.OracleDialect</property>
        <property name="show_sql">true</property>
        <property name="hbm2ddl.auto">create</property>
        <mapping class="com.vaannila.domain.User1" />
    </session-factory>
</hibernate-configuration>

Static java class to establish connection (SessionFactory Helper)

import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class SessionFactoryHelper {
    private static final SessionFactory sessionFactory;

    static {
        try {            
            /*
             * Build a SessionFactory object from session-factory configuration 
             * defined in the hibernate.cfg.xml file. In this file we register 
             * the JDBC connection information, connection pool, the hibernate 
             * dialect that we used and the mapping to our hbm.xml file for each 
             * POJO (Plain Old Java Object).
             * 
             */
            sessionFactory = new Configuration().configure().buildSessionFactory();
        } catch (Throwable e) {
            System.err.println("Error in creating SessionFactory object." 
                + e.getMessage());
            throw new ExceptionInInitializerError(e);
        }
    }

    /*
     * A static method for other application to get SessionFactory object 
     * initialized in this helper class.
     * 
     */
    public static SessionFactory getSessionFactory() {
        return sessionFactory;
    }
}

Bean class

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

@Entity
@Table(name="USER1")
public class User1 {

    private Long id;
    private String name;
    private String gender;
    private String country;
    private String aboutYou;
    private Boolean mailingList;

    @Id
    @GeneratedValue
    @Column(name="USER_ID") 
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }

    @Column(name="USER_NAME")
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }

    @Column(name="USER_GENDER")
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }

    @Column(name="USER_COUNTRY")
    public String getCountry() {
        return country;
    }
    public void setCountry(String country) {
        this.country = country;
    }

    @Column(name="USER_ABOUT_YOU")
    public String getAboutYou() {
        return aboutYou;
    }
    public void setAboutYou(String aboutYou) {
        this.aboutYou = aboutYou;
    }

    @Column(name="USER_MAILING_LIST")
    public Boolean getMailingList() {
        return mailingList;
    }
    public void setMailingList(Boolean mailingList) {
        this.mailingList = mailingList;
    }

}

Answer 1

hibernate.cfg.xml

File hibernate.cfg.xml is fine. It may look confusing that version is still 3.0 in hibernate-configuration-3.0.dtd, but thats how it is. DTD was not updated. Maybe you want to use names names prefixed with hibernate instead, for example hibernate.show_sql instead of show_sql. Names of properties can be found from documentation. Usually DTD_location used is http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd (vs. ..sourceforge...), but both should work.

Building session factory

As you see from the API, buildSessionFactory is deprecated. This is how it is built in 4.x:

Configuration conf = new Configuration();
conf.configure();
serviceRegistry = new ServiceRegistryBuilder().applySettings(conf.getProperties()).buildServiceRegistry();        
sessionFactory = configuration.buildSessionFactory(serviceRegistry);

In many places in documentation this is still not up to date.

Annotating entities

In general no changes are needed to your mappings in bean class. Reason is that you are using normal JPA mappings and also Hibernate 3 is implementation of what is described in JPA specification.