Which annotation is used to generate primary key in spring boot?

In Spring Boot (and more broadly in Java Persistence API (JPA) applications), the @Id annotation is used to mark a field as the primary key of an entity. To automatically generate the value for this primary key, you can use the @GeneratedValue annotation in conjunction with @Id.

Here’s a brief overview of how these annotations are used:

@Id Annotation

• Purpose: Specifies the primary key of an entity.
• Usage: Applied to the field that should act as the primary key of the entity.

@GeneratedValue Annotation

• Purpose: Specifies the strategy for generating the primary key values.
• Usage: Applied to the same field as @Id to define how the primary key values should be generated.

 

@Entity

public class User {

     @Id

    @GeneratedValue(strategy = GenerationType.IDENTITY)  // or other strategy

    private Long id;

   

    // other fields, getters, setters

}

Generation Strategies

The @GeneratedValue annotation supports several strategies:

1.     GenerationType.AUTO: The persistence provider will choose the appropriate strategy for the database. This is the default if no strategy is specified.

@GeneratedValue(strategy = GenerationType.AUTO)

2.     GenerationType.IDENTITY: Uses an auto-incrementing column in the database. This is often used with databases like MySQL.

@GeneratedValue(strategy = GenerationType.IDENTITY)

3.     GenerationType.SEQUENCE: Uses a database sequence to generate unique values. This is commonly used with databases like Oracle.

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

@SequenceGenerator(name = "user_seq", sequenceName = "user_sequence", allocationSize = 1)