Session 39 - Hibernate - Part 1

Java & JEE Training
Session 39 – Hibernate (Part 1 of 2)

Classification: Restricted
Hibernate
• Hibernate framework simplifies the development of java application to
interact with the database.
• Hibernate is an open source, lightweight, ORM (Object Relational
Mapping) tool.
• An ORM tool simplifies the data creation, data manipulation and data
access. It is a programming technique that maps the object to the data
stored in the relational database.

Advantages of Hibernate
• Open-source and Lightweight: Hibernate framework is open-source and
lightweight.
• Fast performance: The performance of hibernate framework is fast because cache
is internally used in hibernate framework. There are two types of cache in hibernate
framework first level cache and second level cache. First level cache is enabled by
default.
• Database Independent query: HQL (Hibernate Query Language) is the object-
oriented version of SQL. It generates the database independent queries. So you
don't need to write database specific queries. Before Hibernate, If database is
changed for the project, we need to change the SQL query as well that leads to the
maintenance problem.
• Automatic table creation: Hibernate framework provides the facility to create the
tables of the database automatically. So there is no need to create tables in the
database manually.
• Simplifies complex join: To fetch data form multiple tables is easy in hibernate
framework.
• Provides query statistics and database status: Hibernate supports Query cache and
provide statistics about query and database status.

Hibernate Architecture – High Level

Hibernate – Detailed Architecture

Hibernate Architecture – Important Elements
• SessionFactory
The SessionFactory is a factory of session and client of ConnectionProvider. It holds second
level cache (optional) of data. The org.hibernate.SessionFactory interface provides factory
method to get the object of Session.
• Session
The session object provides an interface between the application and data stored in the
database. It is a short-lived object and wraps the JDBC connection. It is factory of
Transaction, Query and Criteria. It holds a first-level cache (mandatory) of data. The
org.hibernate.Session interface provides methods to insert, update and delete the object. It
also provides factory methods for Transaction, Query and Criteria.
• Transaction
The transaction object specifies the atomic unit of work. It is optional. The
org.hibernate.Transaction interface provides methods for transaction management.
• ConnectionProvider
It is a factory of JDBC connections. It abstracts the application from DriverManager or
DataSource. It is optional.
• TransactionFactory
It is a factory of Transaction. It is optional.

Hibernate jar files…
• Download from Hibernate official site
http://hibernate.org/orm/downloads/

Hibernate tools download
• http://tools.jboss.org/downloads/

Your first Hibernate project
• Create the java project
• Add jar files for hibernate
• Create the Persistent class
• Create the mapping file for Persistent class
• Create the Configuration file
• Create the class that retrieves or stores the persistent object
• Run the application

Your first Hibernate project – Steps in detail
• Create the java project by File Menu - New - project - java project . Now
specify the project name e.g. firsthb then next - finish
• To add the jar files Right click on your project - Build path - Add external
archives. In this example, we are connecting the application with oracle
database. So you must add the ojdbc14.jar file as well.

//Create the POJO class
public class Employee {
private int id;
private String firstName,lastName;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
}

• Mapping file for POJO - employee.hbm.xml
<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="Employee" table="emp1000">
<id name="id">
<generator class="assigned"></generator>
</id>
<property name="firstName"></property>
<property name="lastName"></property>
</class>
</hibernate-mapping>
** INSTEAD OF WRITING A SEPARATE MAPPING FILE, GIVE MAPPING INFO IN THE POJO ITSELF

• Create entry in configuration file: 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="dialect">org.hibernate.dialect.Oracle9Dialect</property>
<property name="connection.url">jdbc:oracle:thin:@localhost:1521:xe</property>
<property name="connection.username">system</property>
<property name="connection.password">oracle</property>
<property name="connection.driver_class">oracle.jdbc.driver.OracleDriver</property>
<mapping resource="employee.hbm.xml"/>
<mapping resource=“department.hbm.xml"/>
</session-factory>
</hibernate-configuration>

Your first Hibernate project – Steps – HibernateUtil
import org.hibernate.SessionFactory;
import org.hibernate.cfg.AnnotationConfiguration;
public class HibernateUtil
{
private static final SessionFactory sessionFactory;
static{
try{
sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory();
}
catch(Throwable th){
System.err.println("Initial SessionFactory creation failed"+th);
throw new ExceptionInInitializerError(th);
}
}
public static SessionFactory getSessionFactory(){
return sessionFactory;
}
}

CRUD operations: Create
//Create student entity object
Student student = new Student();
student.setStudentName(“Bill Clinton");
student.setRollNumber(01);
student.setCourse("MCA");
//Create session factory object
SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
//getting session object from session factory
Session session = sessionFactory.openSession();
//getting transaction object from session object
session.beginTransaction();
session.save(student);
System.out.println("Inserted Successfully");
session.getTransaction().commit();
session.close();
sessionFactory.close();

CRUD operations: Read
Query query = session.createQuery("from Student");
List students = query.list();
for(Student student : students) {
System.out.println("Roll Number: "+student.getRollNumber()+", Student
Name: "+student.getStudentName()+", Course: "+student.getCourse());
}

CRUD operations: Update
Student student = (Student)session.get(Student.class, 2);
student.setStudentName(“Pawan Kumar");
System.out.println("Updated Successfully");

CRUD operations: Delete
Student student = (Student)session.load(Student.class, 4);
session.delete(student);
System.out.println("Deleted Successfully");

To run the hibernate application, right click on the StoreData class - Run As -
Java Application.

Hibernate with Annotations
• The hibernate application can be created with annotation. There are many
annotations that can be used to create hibernate application such as
@Entity, @Id, @Table etc.
• Hibernate Annotations are based on the JPA 2 specification and supports all
the features.
• All the JPA annotations are defined in the javax.persistence.* package.
Hibernate EntityManager implements the interfaces and life cycle defined
by the JPA specification.
• The core advantage of using hibernate annotation is that you don't need
to create mapping (hbm) file. Here, hibernate annotations are used to
provide the meta data.

• Add the jar file for oracle (if your database is oracle) and annotation
o hibernate-commons-annotations.jar
o ejb3-persistence.jar
o hibernate-annotations.jar
• Create the Persistent class
• Annotations used:
o @Entity annotation marks this class as an entity.
o @Table annotation specifies the table name where data of this entity is to be
persisted. If you don't use @Table annotation, hibernate will use the class name as
the table name by default.
o @Id annotation marks the identifier for this entity.
o @Column annotation specifies the details of the column for this property or field. If
@Column annotation is not specified, property name will be used as the column
name by default.
• Add mapping of Persistent class in configuration file
• Create the class that retrieves or stores the persistent object

@Entity
@Table(name= "emp500")
public class Employee {
@Id
private int id;
private String firstName,lastName;
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
}

Exercise of Web application using Hibernate…
• Create a web application with hibernate. For creating the web application,
we are using JSP for presentation logic, Bean class for representing data
and DAO class for database access code.
• As we create the simple application in hibernate, we don't need to perform
any extra operations in hibernate for creating web application. In such case,
we are getting the value from the user using the JSP file.

DAO Design Pattern in Java

Topics to be covered in next session
• Generator Class in Hibernate
• SQL Dialects
• Collection Mapping
• One-to-one Mapping
• Cascade Types
• Many to one / One to many
• Hibernate Lazy Loading
• Transaction Management
• HQL – Hibernate Query Language
• HCQL – Hibernate Criteria Query Language
• Hibernate Caching

Thank you!

Session 39 - Hibernate - Part 1

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Session 39 - Hibernate - Part 1