What is the difference between JPA and Hibernate?

JPA (Java Persistence API) is a specification or standard that defines an API for object-relational mapping (ORM) and persistence in Java applications. It provides a set of interfaces and annotations.

Hibernate is one of the most popular implementations of the JPA specification. It offers a specific ORM framework that implements all the features defined in JPA, as well as adding its own additional capabilities.

Thus, the main difference is:

• JPA is an interface (specification) that defines how to work with data.
• Hibernate is an implementation of this interface (a specific framework).

This can be compared to the Java Collection Framework: List is an interface (like JPA), and ArrayList or LinkedList are implementations (like Hibernate). You can write code using JPA interfaces and then choose any implementation (for example, Hibernate, EclipseLink) without needing to change most of your persistence-related code.

Key points:

• JPA defines standard APIs for ORM.
• Hibernate implements this standard and adds its own extensions.
• An application written using only the JPA API can easily switch to another JPA implementation.

// Example of using a JPA annotation
import javax.persistence.*;

@Entity
@Table(name = "users")
public class User {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "username")
    private String username;

    // getters and setters
}

This code uses annotations from the javax.persistence package, which are part of the JPA specification. The same code will work with any JPA implementation, including Hibernate.