Why We Use @Transactional in Our Project

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What is @transactional?

@transactional is a Spring annotation used to define a method or class as part of a transaction. This ensures that multiple database operations are executed atomically—either all succeed or none are applied, maintaining the integrity of the data.

Why Implement @transactional?

In our project, we use @transactional to ensure database consistency during operations like user registration, password reset, and updates. Without it, partial updates could be made to the database if an error occurs mid-process. Using @transactional ensures that if an operation fails, all changes are rolled back, keeping the database in a consistent state.

Example: User Password Reset

Without @transactional:

public ResponseEntity<ResetPasswordResponseDTO> resetPassword(ResetPasswordDTO request, String token) {
    User user = userRepository.findByPhoneNumber(jwtService.getUserIdentifierFromToken(token))
            .orElseThrow(() -> new UserNotFoundException("User not found"));
    
    if (!passwordEncoder.matches(request.getCurrentPassword(), user.getPassword())) {
        throw new IncorrectPasswordException("Current password is incorrect.");
    }

    user.setPassword(passwordEncoder.encode(request.getNewPassword()));
    userRepository.save(user);

    return ResponseEntity.ok(new ResetPasswordResponseDTO("Password updated successfully."));
}

In the above method, if an error occurs (e.g., userRepository.save() fails), the changes made to the user’s password would still persist, potentially causing inconsistency.

With @transactional:

@Transactional
public ResponseEntity<ResetPasswordResponseDTO> resetPassword(ResetPasswordDTO request, String token) {
    User user = userRepository.findByPhoneNumber(jwtService.getUserIdentifierFromToken(token))
            .orElseThrow(() -> new UserNotFoundException("User not found"));
    
    if (!passwordEncoder.matches(request.getCurrentPassword(), user.getPassword())) {
        throw new IncorrectPasswordException("Current password is incorrect.");
    }

    user.setPassword(passwordEncoder.encode(request.getNewPassword()));
    userRepository.save(user);

    return ResponseEntity.ok(new ResetPasswordResponseDTO("Password updated successfully."));
}

In this version, if an exception is thrown during any step, the transaction is rolled back, and no changes are made to the database, preserving consistency.

Conclusion

By using @transactional, we ensure that all database changes within a method are executed atomically. If any error occurs, the transaction is rolled back, keeping the database in a consistent state and avoiding partial updates.