What is the difference between JPA and Hibernate?

JPA (Java Persistence API) is a Java specification that defines how to manage relational data in Java applications. It provides a set of interfaces and annotations for ORM (Object-Relational Mapping).

Hibernate is a popular open-source library that is one of the implementations of the JPA specification. It offers concrete classes and methods for managing data persistence.

The main difference is that JPA is a standard, while Hibernate is a specific implementation of that standard. JPA provides an abstraction that allows developers to write code that is not tied to a particular ORM library. Hibernate, in turn, provides the actual logic to implement this abstraction, including database connection, SQL query generation, and session management.

It can be compared to an interface and a class in Java: JPA is the interface PersistanceProvider, and Hibernate is one of the classes implementing this interface.

Example:

// Using JPA interface
EntityManagerFactory emf = Persistence.createEntityManagerFactory("my-persistence-unit");
EntityManager em = emf.createEntityManager();

// Using a specific Hibernate implementation (directly, which is less preferred when using Spring)
// SessionFactory factory = new Configuration().configure().buildSessionFactory();
// Session session = factory.openSession();

Key points:

• JPA: Specification, set of APIs.
• Hibernate: JPA implementation, a specific library.
• JPA allows switching between different ORM implementations.
• Hibernate provides additional features not included in the JPA specification but is compatible with it.