How does object-relational mapping integrate with a database and what are its main principles?

Object-Relational Mapping (ORM) integrates with a database through an abstraction layer that converts programming code objects into relational tables and vice versa.

Key principles of ORM:

• Object-to-table mapping: Each class corresponds to a table in the database, and each property corresponds to a column.
• Relationship management: ORM supports relationships between objects (one-to-one, one-to-many, many-to-many) and converts them into appropriate relational links.
• Queries and transactions: ORM provides an API for creating, reading, updating, and deleting data without writing SQL, automatically generating the necessary queries.
• Caching and optimization: ORM can cache objects and optimize queries to improve performance.

Example of using ORM in Java with JPA:

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

// Fetching a user by ID
User user = entityManager.find(User.class, 1L);

Thus, ORM simplifies working with the database, allowing developers to work with objects rather than directly with SQL queries.