Interview question

What is the difference between JDBC and an ORM like Hibernate? JDBC और Hibernate जैसे ORM में क्या अंतर है?

Answer

Aspect	JDBC	Hibernate (ORM)
Abstraction level	Low-level, direct SQL	High-level, objects mapped to tables
SQL writing	Manual, full control	Auto-generated (HQL/JPQL or Criteria API)
Boilerplate	More - manual ResultSet mapping	Less - automatic object mapping
Caching	None built-in	Built-in first/second-level caching
Database portability	SQL often database-specific	More portable via dialect abstraction

// JDBC - manual mapping from ResultSet to object
PreparedStatement pstmt = conn.prepareStatement('SELECT * FROM users WHERE id = ?');
pstmt.setInt(1, userId);
ResultSet rs = pstmt.executeQuery();
User user = null;
if (rs.next()) {
    user = new User();
    user.setId(rs.getInt('id'));
    user.setName(rs.getString('name'));
    user.setEmail(rs.getString('email'));
}

// Hibernate (ORM) - object-relational mapping via annotations
@Entity
@Table(name = 'users')
class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String name;
    private String email;
    // getters/setters
}

// Fetching with Hibernate - no manual SQL or ResultSet mapping needed
Session session = sessionFactory.openSession();
User user2 = session.get(User.class, userId);

// HQL (Hibernate Query Language) - object-oriented, not raw SQL
Query<User> query = session.createQuery('FROM User WHERE email = :email', User.class);
query.setParameter('email', 'john@example.com');
User result = query.uniqueResult();

// When to use which:
// JDBC: fine-grained control, performance-critical raw queries, simple apps
// Hibernate/JPA: complex domain models, less boilerplate, faster development

पहलू	JDBC	Hibernate (ORM)
Abstraction level	Low-level, direct SQL	High-level, objects tables से mapped
SQL लिखना	Manual	Auto-generated
Caching	Built-in नहीं	Built-in caching

// JDBC - manual mapping
PreparedStatement pstmt = conn.prepareStatement('SELECT * FROM users WHERE id = ?');
pstmt.setInt(1, userId);
ResultSet rs = pstmt.executeQuery();
User user = null;
if (rs.next()) {
    user = new User();
    user.setId(rs.getInt('id'));
    user.setName(rs.getString('name'));
}

// Hibernate (ORM) - annotations से mapping
@Entity
@Table(name = 'users')
class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;
    private String name;
    private String email;
}

Session session = sessionFactory.openSession();
User user2 = session.get(User.class, userId);

Query<User> query = session.createQuery('FROM User WHERE email = :email', User.class);
query.setParameter('email', 'john@example.com');
User result = query.uniqueResult();

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