@OneToOne relationship in Spring Boot - Mini Project: Build & Apply

Create a @OneToOne Relationship in Spring Boot

📖 Scenario: You are building a simple Spring Boot application to manage users and their profiles. Each user has exactly one profile, and each profile belongs to exactly one user.

🎯 Goal: Build two entity classes User and UserProfile with a @OneToOne relationship between them using Spring Boot and JPA annotations.

📋 What You'll Learn

Create a User entity with fields id and username

Create a UserProfile entity with fields id and bio

Add a @OneToOne relationship from User to UserProfile

Use @JoinColumn to specify the foreign key column in User

Ensure the code compiles and follows Spring Boot JPA entity conventions

💡 Why This Matters

🌍 Real World

One-to-one relationships are common in applications where two entities have a direct and exclusive link, such as a user and their profile, or a person and their passport.

💼 Career

Understanding how to model and implement @OneToOne relationships is essential for backend developers working with Spring Boot and JPA to build relational data models.

1

Create the User entity

Create a class called User annotated with @Entity. Add private fields Long id annotated with @Id and @GeneratedValue, and String username. Add public getters and setters for both fields.

Spring Boot

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

Need a hint?

Use @Entity on the class. Use @Id and @GeneratedValue(strategy = GenerationType.IDENTITY) on the id field.

2

Create the UserProfile entity

Create a class called UserProfile annotated with @Entity. Add private fields Long id annotated with @Id and @GeneratedValue, and String bio. Add public getters and setters for both fields.

Spring Boot

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

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

Need a hint?

Use @Entity on the class. Use @Id and @GeneratedValue(strategy = GenerationType.IDENTITY) on the id field.

3

Add @OneToOne relationship in User

In the User class, add a private field UserProfile profile annotated with @OneToOne and @JoinColumn(name = "profile_id"). Add public getter and setter for profile.

Spring Boot

import jakarta.persistence.OneToOne;
import jakarta.persistence.JoinColumn;

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

    // Your code here
}

Need a hint?

Use @OneToOne and @JoinColumn(name = "profile_id") on the profile field in User.

4

Complete the @OneToOne relationship setup

Ensure both User and UserProfile classes are in the same package and properly imported. Add @Entity annotations and all necessary imports. Confirm the code compiles without errors.

Spring Boot

// Review your code and add any missing imports or annotations
// Your code here

Need a hint?

Make sure all imports and annotations are present and both classes are complete.