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Spring Boot One-to-One Mapping
A One-to-One relationship means one entity is associated with exactly one other entity.
Example:
✅ A User has exactly one Profile
✅ A Profile belongs to exactly one User
Define User and Profile Entities
We'll create a bidirectional relationship where both User and Profile reference each other.
User.java
import jakarta.persistence.*;
@Entity
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
@OneToOne(cascade = CascadeType.ALL)
@JoinColumn(name = "profile_id", referencedColumnName = "id")
private Profile profile;
// Getters and Setters
public Long getId() { return id; }
public void setId(Long id) { this.id = id; }
public String getName() { return name; }
public void setName(String name) { this.name = name; }
public Profile getProfile() { return profile; }
public void setProfile(Profile profile) { this.profile = profile; }
}
✅ @OneToOne(cascade = CascadeType.ALL) → Ensures changes in User also apply to Profile.
✅ @JoinColumn(name = "profile_id") → Defines the foreign key column in the User table.
Profile.java
import jakarta.persistence.*;
@Entity
public class Profile {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String bio;
private String phone;
// Getters and Setters
public Long getId() { return id; }
public void setId(Long id) { this.id = id; }
public String getBio() { return bio; }
public void setBio(String bio) { this.bio = bio; }
public String getPhone() { return phone; }
public void setPhone(String phone) { this.phone = phone; }
}
Table name : profile
| id | bio | phone |
|---|
Table name : user
| id | name | profile_id |
|---|
Create JPA Repositories
UserRepository.java
import org.springframework.data.jpa.repository.JpaRepository;
public interface UserRepository extends JpaRepository<User, Long> {
}
ProfileRepository.java
import org.springframework.data.jpa.repository.JpaRepository;
public interface ProfileRepository extends JpaRepository<Profile, Long> {
}
Create Services
UserService.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class UserService {
@Autowired
private UserRepository userRepository;
@Autowired
private ProfileRepository profileRepository;
}
ProfileService.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class ProfileService {
@Autowired
private ProfileRepository profileRepository;
}
Create Controllers
ProfileController.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping("/profiles")
public class ProfileController {
@Autowired
private ProfileService profileService;
}
UserController.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping("/users")
public class UserController {
@Autowired
private UserService userService;
}
Create REST API Controller for Profile
ProfileController.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
@RestController
@RequestMapping("/profiles")
public class ProfileController {
@Autowired
private ProfileService profileService;
// ✅ Create Profile
@PostMapping
public Profile addUser(@RequestBody Profile profile) {
return profileService.saveProfile(profile);
}
// ✅ Get All Users
@GetMapping
public List<Profile> getUsers() {
return profileService.getAllProfiles();
}
// ✅ Get Profile by ID
@GetMapping("/{id}")
public Profile getUser(@PathVariable Long id) {
return profileService.getProfileById(id);
}
// ✅ Update Profile
@PutMapping
public Profile updateUser(@RequestBody Profile profile) {
return profileService.updateProfile(profile);
}
// ✅ Delete Profile
@DeleteMapping("/{id}")
public String deleteUser(@PathVariable Long id) {
return profileService.deleteProfile(id);
}
}
ProfileService.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
import java.util.Optional;
@Service
public class ProfileService {
@Autowired
private ProfileRepository profileRepository;
// ✅ Create Profile
public Profile saveProfile(Profile profile) {
return profileRepository.save(profile);
}
// ✅ Get All Profiles
public List<Profile> getAllProfiles() {
return profileRepository.findAll();
}
// ✅ Get Profile by ID
public Profile getProfileById(Long id) {
return profileRepository.findById(id).orElse(null);
}
// ✅ Update Profile
public Profile updateProfile(Profile profile) {
return profileRepository.save(profile);
}
// ✅ Delete Profile
public String deleteProfile(Long id) {
profileRepository.deleteById(id);
return "Profile deleted!";
}
}
ProfileRepository.java
import org.springframework.data.jpa.repository.JpaRepository;
public interface ProfileRepository extends JpaRepository<Profile, Long> {
}
Testing the REST API with Postman:
Once the application is running, test the endpoints:
Create Profile http://localhost:8080/profiles
Get All Profiles http://localhost:8080/profiles
Get Profile By Id http://localhost:8080/profiles/{profileID}
Update Profile http://localhost:8080/profiles
Delete Profile http://localhost:8080/profiles/{profileID}
Create REST API Controller for User
UserController.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import java.util.List;
@RestController
@RequestMapping("/users")
public class UserController {
@Autowired
private UserService userService;
// ✅ Create User
@PostMapping
public User addUser(@RequestBody User user) {
return userService.saveUser(user);
}
// ✅ Get All Users
@GetMapping
public List<User> getUsers() {
return userService.getAllUsers();
}
// ✅ Get Userby id
@GetMapping("/{id}")
public User getUser(@PathVariable Long id) {
return userService.getUserById(id);
}
// ✅ Update User
@PutMapping
public User updateUser(@RequestBody User user) {
return userService.updateUser(user);
}
// ✅ Delete User By id
@DeleteMapping("/{id}")
public String deleteUser(@PathVariable Long id) {
return userService.deleteUser(id);
}
// ✅ Create User connect with existing profile
@PutMapping("/existingProfile/{profileId}")
public User updateUserWithExistingProfile(@PathVariable Long profileId, @RequestBody User user) {
return userService.createUserWithExistingProfile(profileId, user);
}
// ✅ Update User connect with existing profile
@PutMapping("/existingUserProfile/{profileId}/{userId}")
public User updateUserProfile(@PathVariable Long profileId, @PathVariable Long userId) {
return userService.updateExistingUserProfile(profileId, userId);
}
// ✅ Update profile connected with user
@PutMapping("/{userId}/profile/update-name")
public User updateProfileName(@PathVariable Long userId, @RequestParam String newProfileName) {
return userService.updateUserProfileName(userId, newProfileName);
}
// ✅ Delete profile connected with user set null in profile_id column
@DeleteMapping("/{userId}/profile")
public User removeProfile(@PathVariable Long userId) {
return userService.removeUserProfile(userId);
}
}
UserService.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import java.util.List;
import java.util.Optional;
@Service
public class UserService {
@Autowired
private UserRepository userRepository;
@Autowired
private ProfileRepository profileRepository;
// ✅ Create User
public User saveUser(User user) {
return userRepository.save(user);
}
// ✅ Get All Users
public List<User> getAllUsers() {
return userRepository.findAll();
}
// ✅ Get User by id
public User getUserById(Long id) {
return userRepository.findById(id).orElse(null);
}
// ✅ Update User
public User updateUser(User user) {
return userRepository.save(user);
}
// ✅ Delete User By id
public String deleteUser(Long id) {
userRepository.deleteById(id);
return "User deleted!";
}
// ✅ Create User connect with existing profile
public User createUserWithExistingProfile(Long profileId, User user) {
if (profileId != null) {
Optional<Profile> existingProfile = profileRepository.findById(profileId);
existingProfile.ifPresent(user::setProfile);
}
return userRepository.save(user);
}
// ✅ Update User connect with existing profile
public User updateExistingUserProfile(Long profileId, Long userId) {
if (profileId != null && userId != null) {
Optional<Profile> existingProfile = profileRepository.findById(profileId);
Optional<User> existingUser = userRepository.findById(userId);
if (existingUser.isPresent() && existingProfile.isPresent()) {
User user = existingUser.get();
user.setProfile(existingProfile.get());
return userRepository.save(user);
}
}
return null;
}
// ✅ Update profile connected with user
public User updateUserProfileName(Long userId, String newProfileName) {
Optional<User> existingUser = userRepository.findById(userId);
if (existingUser.isPresent()) {
User user = existingUser.get();
Profile profile = user.getProfile();
if (profile != null) {
profile.setBio(newProfileName); // Update profile name (bio)
profileRepository.save(profile); // Save updated profile
return user;
} else {
throw new RuntimeException("Profile not found for User ID: " + userId);
}
} else {
throw new RuntimeException("User not found with ID: " + userId);
}
}
// ✅ Delete profile connected with user set null in profile_id column
public User removeUserProfile(Long userId) {
Optional<User> existingUser = userRepository.findById(userId);
if (existingUser.isPresent()) {
User user = existingUser.get();
Profile profile = user.getProfile();
if (profile != null) {
user.setProfile(null); // Remove profile from user
userRepository.save(user); // Save updated user (profile detached)
return user;
} else {
throw new RuntimeException("Profile not found for User ID: " + userId);
}
} else {
throw new RuntimeException("User not found with ID: " + userId);
}
}
}
UserRepository.java
import org.springframework.data.jpa.repository.JpaRepository;
public interface UserRepository extends JpaRepository<User, Long> {
}
Testing the REST API with Postman:
Once the application is running, test the endpoints:
Create User With Profile http://localhost:8080/users
Get All Users With Profile http://localhost:8080/users
Get Users With Profile by user id http://localhost:8080/users/{userID}
Update Users http://localhost:8080/users
Delete Users http://localhost:8080/users/{userID}
Create Users with existing profile id http://localhost:8080/users/existingProfile/{profileID}
Update Existing Users With Existing Profile http://localhost:8080/users/existingUserProfile/{profileID}/{userID}
Update Profile by Using User id http://localhost:8080/users/{userID}/profile/update-name?newProfileName=Mobile Developer
Delete Profile by Using User id http://localhost:8080/users/{userID}/profile
