@Id and @GeneratedValue for primary keys in Spring Boot - Mini Project: Build & Apply

Using @Id and @GeneratedValue for Primary Keys in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage a list of books. Each book needs a unique identifier to keep track of it in the database.

🎯 Goal: Create a Book entity class with a primary key field that uses @Id and @GeneratedValue annotations to automatically generate unique IDs for each book.

📋 What You'll Learn

Create a Book class annotated with @Entity

Add a private field id of type Long to serve as the primary key

Annotate the id field with @Id and @GeneratedValue

Use GenerationType.IDENTITY strategy for @GeneratedValue

Add a private field title of type String for the book's title

💡 Why This Matters

🌍 Real World

In real applications, entities need unique IDs to identify records in databases. Using @Id and @GeneratedValue helps automate this process.

💼 Career

Understanding how to define primary keys with auto-generation is essential for backend developers working with Spring Boot and databases.

1

Create the Book entity class with fields

Create a public class called Book annotated with @Entity. Inside it, declare a private Long field named id and a private String field named title.

Spring Boot

@Entity
public class Book {
    // Your code here
}

Need a hint?

Use @Entity above the class. Declare id and title as private fields inside the class.

2

Add @Id annotation to the id field

Add the @Id annotation above the id field in the Book class to mark it as the primary key.

Spring Boot

import jakarta.persistence.Entity;
import jakarta.persistence.Id;

@Entity
public class Book {
    // Add @Id annotation here
    private Long id;
    private String title;
}

Need a hint?

Place @Id directly above the id field.

3

Add @GeneratedValue with IDENTITY strategy

Add the @GeneratedValue annotation above the id field with the strategy set to GenerationType.IDENTITY to let the database generate unique IDs automatically.

Spring Boot

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;

@Entity
public class Book {
    @Id
    // Add @GeneratedValue with GenerationType.IDENTITY here
    private Long id;
    private String title;
}

Need a hint?

Use @GeneratedValue(strategy = GenerationType.IDENTITY) above the id field.

4

Add getter and setter methods for id and title

Add public getter and setter methods for both id and title fields in the Book class to allow access and modification.

Spring Boot

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;

@Entity
public class Book {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    private String title;

    // Add getter and setter methods here
}

Need a hint?

Write simple getter and setter methods for both fields.