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Hibernate - @GeneratedValue Annotation in JPA

Last Updated : 05 Apr, 2025

The @GeneratedValue annotation, the name itself suggests that it will generate something. This annotation is generally used in conjunction with the @Id annotation to automatically generate unique values for primary key columns within our database tables. When creating an entity class, we have to specify a primary key for that entity. To mark the field property as a primary key of the entity, we use the @Id annotation. When we apply the @GeneratedValue annotation to our primary key field or property. It will instruct Hibernate to automatically generate a unique value for that field during the process of persisting the entity into the database.

The @GeneratedValue annotation provides us with different strategies for the generation of primary keys, which are as follows : 

1. GenerationType.IDENTITY

• Relies on the database’s auto-increment feature.
• Supported by MySQL, PostgreSQL, SQL Server, etc.
• Example:

@Id

@GeneratedValue(strategy = GenerationType.IDENTITY)

private Long id;

2. GenerationType.SEQUENCE

• Uses a database sequence (Oracle, PostgreSQL).
• Requires a sequence object in the database.
• Example:

@Id

@GeneratedValue(strategy = GenerationType.SEQUENCE)

private Long id;

3. GenerationType.TABLE

• Uses a separate table to simulate sequences.
• Works across all databases but has performance overhead.
• Example:

@Id

@GeneratedValue(strategy = GenerationType.TABLE)

private Long id;

4. GenerationType.AUTO (Default)

• Lets the JPA provider choose the best strategy based on the database.
• Example:

@Id

@GeneratedValue(strategy = GenerationType.AUTO)

private Long id;

5. GenerationType.UUID 

• Generates a Universally Unique Identifier (UUID) compliant with RFC 4122.
• Ideal for distributed systems where uniqueness across databases is required.
• Example:

@Id

@GeneratedValue(strategy = GenerationType.UUID)

private String id; // Stored as VARCHAR(36) or BINARY(16)

Example 1: Using IDENTITY

package com.example.java_test_application;

// on the below line creating an entity class for the class
// of Employee.
@Entity
public class Employee {
    // on the below line creating an employee id generated
    // value with the strategy for generation type.
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long empId;

    private String employeeName;

    private String employeeQualification;
}

Explanation:

In the above example, we are considering an Employee entity. Inside this entity, we are marking empID with @Id annotation to indicate it as a primary key. The @GeneratedValue annotation with GenerationType Identity indicates that the primary key will be generated automatically by the database. The @GenaratedValue annotation simplifies generating unique primary key values and allows persistence providers to handle this task automatically, reducing boilerplate code needed for managing the primary keys in the database. 

Example 2: Using SEQUENCE

// on the below line creating an entity class for the class
// of Department.
@Entity
public class Department {
    // on the below line creating a variable for department
    // id.
    @Id
    @GeneratedValue(strategy = GenerationType.SEQUENCE)
    private Long departmentID;

    // on the below line creating a variable for department
    // name.
    private String departmentName;
}

Explanation:

In the above example, we are considering a Department entity. Inside this entity, we are marking departmentID with @Id annotation to indicate it as a primary key. The @GeneratedValue annotation with GenerationType SEQUENCE will generate primary key values which require the usage of the database sequence objects.

Example 3: Using UUID

@Entity
public class User {
    @Id
    @GeneratedValue(strategy = GenerationType.UUID)
    private String userId; // e.g., "123e4567-e89b-12d3-a456-426614174000"

    private String username;
}

Generates a unique string ID (no database sequence needed).

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