What is JPA and Hibernate, and what is the difference?

JPA (Java Persistence API) is a Java specification for managing object-relational mapping (ORM). It defines a set of interfaces and rules for working with databases through Java objects, but it does not contain an implementation itself.

Hibernate is one of the most popular implementations of JPA. It provides a concrete mechanism for mapping objects to database tables, managing sessions, caching, and query optimization.

Thus, the difference is that JPA is a standard and a set of interfaces, while Hibernate is a library that implements this standard and adds additional features.

Example of using JPA with Hibernate:

@Entity
public class User {
    @Id
    private Long id;
    private String name;
    // getters and setters
}

// In the service
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
User user = em.find(User.class, 1L);
em.getTransaction().commit();
em.close();