ORM (Object Relational Mapping) is a technique that allows developers to interact with databases using Java objects instead of SQL queries.

Hibernate is a Java ORM framework that simplifies database interaction by mapping classes to tables and automating query generation.

What is ORM and Hibernate in Java | FullStackPrep.Dev

💡 Concept: ORM & Hibernate

ORM (Object Relational Mapping) is a technique that maps Java objects to database tables. Hibernate is a widely used ORM framework in Java that simplifies database access.

📘 Quick Intro

With ORM, you deal with Java objects instead of SQL queries. Hibernate automates table mapping, query generation, caching, and transaction handling through annotations or XML.

🧠 Analogy

Think of ORM like Google Translate between Java and SQL. You write in Java (objects), and Hibernate converts it into SQL behind the scenes and brings back data as objects again.

🔧 Technical Explanation

ORM maps class fields to database columns.
Hibernate uses annotations like @Entity, @Table, @Id, @Column for mapping.
It eliminates boilerplate JDBC code.
Hibernate supports lazy loading, caching, and transactions.
It can be used standalone or with JPA (Java Persistence API).

🎯 Use Cases

✅ Rapid application development with database access
✅ CRUD operations without writing raw SQL
✅ Enterprise apps with complex object-relational models

💻 Example: Hibernate ORM Mapping


import jakarta.persistence.*;

@Entity
@Table(name = "users")
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int id;

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

    // Getters and Setters
}

❓ Interview Q&A

Q1: What is ORM?
A: A way to map Java objects to database tables.

Q2: What is Hibernate?
A: A popular Java ORM framework.

Q3: What annotation makes a class an entity?
A: @Entity.

Q4: Can Hibernate work with JPA?
A: Yes, it is a JPA implementation.

Q5: Does Hibernate eliminate SQL completely?
A: No, but it minimizes its use.

Q6: What is lazy loading in Hibernate?
A: Defers loading of objects until needed.

Q7: How are primary keys defined?
A: Using @Id.

Q8: What is HQL?
A: Hibernate Query Language, similar to SQL but works with objects.

Q9: What is a session in Hibernate?
A: A unit of interaction between the app and DB.

Q10: Can Hibernate cache objects?
A: Yes, via first and second-level caches.

📝 MCQs

Q1. What does ORM stand for?

Object Resource Map
Object Relational Mapping
Open Relational Model
Object Random Mapper

Q2. Which annotation makes a class an entity?

@Bean
@Model
@Entity
@Class

Q3. What is Hibernate?

A compiler
A servlet
An ORM framework
A JVM

Q4. What is HQL?

Hibernate Quick Link
High-level Query Logic
Hibernate Query Language
Hybrid Query Layer

Q5. What is lazy loading?

Disabling caching
Loading objects only when needed
Multi-threaded loading
Compiling at runtime

Q6. What is @Id used for?

Foreign key
Column mapping
Primary key
Index

Q7. Is Hibernate JPA-compliant?

No
Yes
Partially
Only with Spring

Q8. Does Hibernate support transactions?

No
Yes
Only with JDBC
Only on Linux

Q9. What is @Table used for?

Define DB
Map class to table name
Auto-generate keys
Define column order

Q10. Can you use Hibernate without annotations?

No
Yes, via XML
Only with Spring
Only with JDK 11+

💡 Bonus Insight

Hibernate reduces development time significantly by handling the boilerplate SQL and schema mappings, making it a go-to for enterprise Java apps.

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What is ORM and Hibernate in Java