What is @GeneratedValue Annotation in JPA?

@GeneratedValue is a JPA annotation used to automatically generate primary key values for entity objects.

It works together with:

@Id

annotation to generate unique IDs automatically.

In simple words:

“@GeneratedValue automatically creates unique primary key values for database records.”

Why @GeneratedValue is Needed

Without automatic ID generation:

Developers must manually assign IDs
Duplicate IDs may occur
Primary key conflicts may happen
Database maintenance becomes difficult

@GeneratedValue solves these problems by generating unique IDs automatically.

Basic Example

@Entity
public class Student {

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

    private String name;

    private String email;
}

What Happens Internally?

When a new student is saved:

Developer does not provide ID
Hibernate generates unique ID automatically
Database stores generated ID

Example Save Operation

Student student = new Student();

student.setName("Naresh");

student.setEmail("naresh@gmail.com");

repository.save(student);

Generated Database Record

ID	Name	Email
1	Naresh	naresh@gmail.com

Why @GeneratedValue Works with @Id

@Id identifies the primary key field, while:

@GeneratedValue

generates the primary key value automatically.

Common Syntax

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

Main Generation Strategies

JPA supports multiple ID generation strategies.

GenerationType Strategies

Strategy	Description
IDENTITY	Uses database auto-increment
SEQUENCE	Uses database sequence
TABLE	Uses separate generator table
AUTO	Hibernate chooses automatically

1. IDENTITY Strategy

IDENTITY uses database auto-increment columns.

IDENTITY Example

@GeneratedValue(
    strategy = GenerationType.IDENTITY
)

Generated MySQL Table

CREATE TABLE student (

    id BIGINT AUTO_INCREMENT PRIMARY KEY,

    name VARCHAR(255)

)

When to Use IDENTITY

Commonly used with:

MySQL
SQL Server

Advantages of IDENTITY

Simple configuration
Database handles ID generation
Widely used

Disadvantages of IDENTITY

Batch inserts may be slower
Database-dependent

2. SEQUENCE Strategy

SEQUENCE uses database sequence objects.

SEQUENCE Example

@GeneratedValue(
    strategy = GenerationType.SEQUENCE
)

Sequence Generator Example

@Id
@GeneratedValue(
    strategy = GenerationType.SEQUENCE,
    generator = "student_seq"
)

@SequenceGenerator(
    name = "student_seq",
    sequenceName = "student_sequence",
    allocationSize = 1
)
private Long id;

When to Use SEQUENCE

Commonly used with:

Oracle
PostgreSQL

Advantages of SEQUENCE

Better performance
Efficient batch inserts
More scalable

3. TABLE Strategy

TABLE strategy stores ID values in a separate table.

TABLE Example

@GeneratedValue(
    strategy = GenerationType.TABLE
)

How TABLE Strategy Works

Hibernate creates:

id_generator

table to track ID values.

Disadvantages of TABLE Strategy

Slower performance
Additional table overhead

4. AUTO Strategy

AUTO lets Hibernate choose the best strategy automatically.

AUTO Example

@GeneratedValue(
    strategy = GenerationType.AUTO
)

How AUTO Works

Hibernate selects strategy based on:

Database type
Hibernate dialect

Difference Between Strategies

Strategy	Performance	Database Dependency
IDENTITY	Moderate	High
SEQUENCE	High	Moderate
TABLE	Lower	Low
AUTO	Depends on provider	Moderate

How Hibernate Uses @GeneratedValue

Entity object is created
Hibernate checks ID strategy
Unique ID is generated
Entity is inserted into database

Generated SQL Example

INSERT INTO student(name, email)
VALUES (?, ?)

Database automatically generates:

id

Best Practices for @GeneratedValue

Use IDENTITY for MySQL
Use SEQUENCE for PostgreSQL and Oracle
Prefer Long or UUID for IDs
Avoid manual ID assignment when unnecessary
Keep primary keys immutable

UUID-Based ID Example

Modern applications often use UUIDs.

UUID Example

@Id
@GeneratedValue
private UUID id;

Advantages of @GeneratedValue

Automatic ID generation
Prevents duplicate IDs
Improves scalability
Reduces manual coding
Simplifies database operations

Disadvantages of Improper Strategy Selection

Poor performance
Database compatibility issues
Slower inserts
Complex migrations

Real-Time Example in Banking Application

Banking application contains entities such as:

Customer
Account
Transaction

Each record requires a unique ID, which is generated automatically using:

@GeneratedValue

Difference Between @Id and @GeneratedValue

Feature	@Id	@GeneratedValue
Purpose	Marks primary key	Generates primary key value
Mandatory	Yes	No
Used For	Entity identification	Automatic ID generation

Common Interview Questions on @GeneratedValue