如何在拥有@ManyToMany关系JPA springboot时摆脱循环冗余

@Entity
public class User {
    // ...

    @ManyToMany
    @JsonIgnore
    private List<Role> roles;

    // ...
}

@Entity
public class Role {
    // ...

    @ManyToMany(mappedBy = "roles")
    @JsonIgnore
    private List<User> users;

    // ...
}

@Entity
public class User {
    // ...

    @ManyToMany
    private List<Role> roles;

    // ...
}

@Entity
public class Role {
    // ...

    @ManyToMany(mappedBy = "roles")
    private List<User> users;

    // ...
}

public class UserDTO {
    private Long id;
    private String username;
    // ...

    public UserDTO(User user) {
        this.id = user.getId();
        this.username = user.getUsername();
        // ...
    }

    // getters and setters
}

@RestController
public class UserController {
    // ...

    @GetMapping("/users/{id}")
    public UserDTO getUserById(@PathVariable Long id) {
        User user = userRepository.findById(id).orElse(null);
        if (user != null) {
            return new UserDTO(user);
        }
        return null;
    }

    // ...
}