Can you explain what Java Persistence API is and how it is used to interact with a database?

Java Persistence API (JPA) is a standard interface in Java for managing data persistence, that is, for saving, updating, and retrieving objects from a database. JPA allows working with a database through Java objects, using the ORM (Object-Relational Mapping) concept.

Main components of JPA:

• Entity — a class that maps to a table in the database.
• EntityManager — the primary interface for operations on entities (saving, searching, deleting).
• Persistence Unit — configuration defining connection parameters to the database and settings.

Example of using JPA to save an object:

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String name;

    // getters and setters
}

// In service code
EntityManager em = entityManagerFactory.createEntityManager();
em.getTransaction().begin();
User user = new User();
user.setName("Ivan");
em.persist(user);
em.getTransaction().commit();
em.close();

Thus, JPA simplifies working with the database by allowing manipulation of objects rather than writing SQL directly.