Problems with Lazy Loading in JPA When Using DTOs with Spring Data JPA
I've spent hours debugging this and Does anyone know how to I tried several approaches but none seem to work... I'm working on a personal project and I'm working with an scenario with lazy loading when trying to fetch a list of DTOs using Spring Data JPA... I want to retrieve a `UserDTO` that contains a user's basic information along with a list of their roles. However, when I fetch the users, the roles are not being loaded, and I end up with `null` values for those fields. The DTO is structured as follows: ```java public class UserDTO { private Long id; private String username; private List<String> roles; public UserDTO(Long id, String username, List<String> roles) { this.id = id; this.username = username; this.roles = roles; } // Getters and setters omitted for brevity } ``` My repository method looks like this: ```java @Query("SELECT new com.example.dto.UserDTO(u.id, u.username, r.name) FROM User u JOIN u.roles r") List<UserDTO> findAllUsersWithRoles(); ``` When I call this method, I'm expecting a list of `UserDTO` objects populated with the user's role names. Instead, I am receiving a list where the `roles` field is `null` or empty. I've checked the mapping between the `User` and `Role` entities, and it appears correct: ```java @Entity public class User { @Id private Long id; private String username; @OneToMany(fetch = FetchType.LAZY) private List<Role> roles; } @Entity public class Role { @Id private Long id; private String name; } ``` I've also tried changing the fetch type to `EAGER` in the `User` entity to see if it resolves the scenario, but that leads to performance problems when retrieving many users. Additionally, I've confirmed that the roles are correctly populated in the database. I suspect this might be related to how JPA handles the lazy loading in conjunction with DTO projections. Is there a better approach to fetch the roles along with the users without running into lazy loading issues? Any suggestions would be greatly appreciated! This is part of a larger web app I'm building. I'm working on a CLI tool that needs to handle this. Any ideas what could be causing this? This is for a mobile app running on macOS. Has anyone else encountered this?