First Hibernate Application

Configuring Hibernate

   In this application Hibernate provided connection pooling and transaction management is used for simplicity. Hibernate uses the hibernate.cfg.xml to create the connection pool and setup required environment.

   <?xml version='1.0' encoding='utf-8'?>

  <!DOCTYPE hibernate-configuration PUBLIC"-//Hibernate/Hibernate Configuration DTD//EN"

     "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

<session-factory>

      <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>

      <property name="hibernate.connection.url">

                          jdbc:mysql://localhost/hibernatetutorial</property>

      <property name="hibernate.connection.username">root</property>

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

      <property name="hibernate.connection.pool_size">10</property>

      <property name="show_sql">true</property>

      <property name="dialect">org.hibernate.dialect.MySQLDialect</property>

<property name="hibernate.hbm2ddl.auto">update</property>

      <!-- Mapping files -->

      <mapping resource="contact.hbm.xml"/>

</session-factory>

</hibernate-configuration>

The dialect property  is org.hibernate.dialect.MySQLDialect which tells the Hibernate that we are using MySQL Database. Hibernate supports many database.

The <mapping resource="contact.hbm.xml"/> property is the mapping for our contact table.

 

Writing First Persistence Class

Hibernate uses the Plain Old Java Objects (POJOs) classes to map to the database table. We can configure the variables to map to the database column. Here is the code for Contact.java:

public class Contact {

  private String firstName;

  private String lastName;

  private String email;

  private long id;

  public String getEmail() {     return email;    }

  public String getFirstName() {     return firstName;    }

  public String getLastName() {     return lastName;   }

  public void setEmail(String string) {     email = string;   }

  public void setFirstName(String string) {     firstName = string;   }

  public void setLastName(String string) {     lastName = string;   }

  public long getId() {     return id;   }

  public void setId(long l) {     id = l;   }

}

 

Mapping the Contact Object to the Database Contact table

The file contact.hbm.xml is used to map Contact Object to the Contact table in the database. Here is the code for contact.hbm.xml:

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping>

  <class name="roseindia.tutorial.hibernate.Contact" table="CONTACT">

   <id name="id" type="long" column="ID" >

    <generator class="assigned"/>

   </id>

   <property name="firstName"> <column name="FIRSTNAME" /> </property>

   <property name="lastName"> <column name="LASTNAME"/></property>

   <property name="email"> <column name="EMAIL"/> </property>

  </class>

</hibernate-mapping>

 

Developing Code to Test Hibernate example

Now we are ready to write a program to insert the data into database. We should first understand about the Hibernate's Session. Hibernate Session is the main runtime interface between a Java application and Hibernate. First we are required to get the Hibernate Session.SessionFactory allows application to create the Hibernate Sesssion by reading the configuration from hibernate.cfg.xml file.  Then the save method on session object is used to save the contact information to the database:

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

public class FirstExample {

  public static void main(String[] args) {

    Session session = null;

    try{

      // This step will read hibernate.cfg.xml and prepare hibernate for use

      SessionFactory sessionFactory = new Configuration().configure().buildSessionFactory();

       session =sessionFactory.openSession();

      System.out.println("Inserting Record");

           Contact contact = new Contact();

           contact.setId(3);

           contact.setFirstName("Vijay");

           contact.setLastName("Kumar");

           contact.setEmail("vijay.kumar@sun.com");

           session.save(contact);

           System.out.println("Done");

       }catch(Exception e){

         System.out.println(e.getMessage());

       }finally{

             // Actual contact insertion will happen at this step

                session.flush();

                session.close();

      }

   }

}