👀 Views: 99 💬 Answers: 1 📅 Created: 2025-06-17

spring-boot hibernate exception-handling Java

I'm integrating two systems and I'm collaborating on a project where I've been struggling with this for a few days now and could really use some help... I'm facing a `LazyInitializationException` when trying to access a related entity in my Spring Boot application using Hibernate. I have a situation where I am fetching a list of `UserDTO` objects that aggregate data from `User` and `Profile` entities. The issue arises when I try to access the `profile` field of `UserDTO` after the session is closed. I have the following code in my `UserService`: ```java @Service public class UserService { @Autowired private UserRepository userRepository; @Transactional(readOnly = true) public List<UserDTO> getAllUsers() { List<User> users = userRepository.findAll(); return users.stream().map(this::convertToDTO).collect(Collectors.toList()); } private UserDTO convertToDTO(User user) { UserDTO dto = new UserDTO(); dto.setId(user.getId()); dto.setName(user.getName()); dto.setProfile(user.getProfile()); // This is where the issue happens return dto; } } ``` The `User` entity has a `@OneToOne` relationship with the `Profile` entity: ```java @Entity public class User { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private String name; @OneToOne(fetch = FetchType.LAZY) private Profile profile; } ``` When I call `getAllUsers()`, the transaction is closed by the time I try to access `profile`, which causes the `LazyInitializationException`. I've tried changing the fetch type to `EAGER`, but that leads to performance issues due to a Cartesian product in the SQL queries when there are many users. I also tried using `JOIN FETCH` in the repository method: ```java @Query("SELECT u FROM User u JOIN FETCH u.profile") List<User> findAll(); ``` This works but defeats the purpose of using DTOs since I'm fetching all data at once. How can I handle this scenario properly while still using DTOs, without running into the `LazyInitializationException`? Any best practices or suggestions would be greatly appreciated! This is part of a larger API I'm building. Has anyone else encountered this? This is my first time working with Java latest. Hoping someone can shed some light on this. This is for a application running on Windows 11. Thanks for any help you can provide!