Java Persistence with Hibernate

Hibernate is a powerful Object-Relational Mapping (ORM) framework for Java that simplifies database interaction. It bridges the gap between object-oriented programming and relational databases, allowing developers to work with Java objects and have them seamlessly persisted to the database.

Hibernate uses annotations or XML configuration to map Java classes to database tables. This process is known as Object-Relational Mapping (ORM). By defining mappings, Hibernate takes care of generating SQL queries and managing database operations, relieving developers from writing boilerplate code.

import javax.persistence.*;

@Entity
@Table(name = “employees”)
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

@Column(name = “full_name”)
private String fullName;

// Getters and setters
}

In this example, the Employee class is annotated with @Entity, indicating that it represents a database entity. The @Table annotation specifies the table name, and @Id and @GeneratedValue define the primary key and its generation strategy.

Hibernate simplifies CRUD (Create, Read, Update, Delete) operations, making it easier to interact with the database.

public class EmployeeDAO {
private EntityManager entityManager;

public EmployeeDAO(EntityManager entityManager) {
this.entityManager = entityManager;
}

public Employee findById(Long id) {
return entityManager.find(Employee.class, id);
}

public void save(Employee employee) {
entityManager.getTransaction().begin();
entityManager.persist(employee);
entityManager.getTransaction().commit();
}

public void update(Employee employee) {
entityManager.getTransaction().begin();
entityManager.merge(employee);
entityManager.getTransaction().commit();
}

public void delete(Employee employee) {
entityManager.getTransaction().begin();
entityManager.remove(employee);
entityManager.getTransaction().commit();
}
}

In this example, we create a EmployeeDAO class responsible for CRUD operations. The EntityManager obtained from Hibernate’s session manages the transactions and database interactions.