How should I design endpoint to return different models depending on User role in Spring - spring

Question

So lets assume I have 2 model classes - User and Presentation, and they look something like this:
#Entity
public class Presentation {
#Id
private Long id;
#ManyToOne
#JoinColumn(name = "user_id")
private User user;
}
#Entity
public class User implements UserDetails {
#Id
private Long id;
private String username;
private String name;
private String surname;
private String password;
#Enumerated(EnumType.STRING)
private Role role;
}
As you can see I have a unidirectional mapping for user in Presentation class. My endpoint looks something like this:
#RestController
public class PresentationController {
#GetMapping("/{presentationId}")
public PresentationDTO getPresentation(#PathVariable Long presentationId) {
return presentationService.getPresentationById(presentationId);
}
#GetMapping
public List<PresentationDTO> getAllPresentations() {
return presentationService.getAllPresentations();
}
}
Now for my question - how do I change getAllPresentations() to return the presentations that the users with role "user" own, and return all presentations for users with role "admin"? I know I can create a separate endpoint with a different mapping (like /admin/presentations) and add #PreAuthorize(hasRole("admin")), but here is the tricky part.
For the getAllPresentations() endpoint which everyone who is authenticated is supposed to fetch his own presentations, how do I know for which user I have to return his presentations? Maybe I can get the username as a parameter but that might be dangerous cause he can submit any username he wants and get the presentations for that user. I don't know too much about Spring Security and I don't even know the right question to ask google to get an answer so I'm stuck...
Any help will be appreciated, thanks!

Answer 1

You don't have to pass username to your controller method. The currently authenticated user is available through a number of different mechanisms in Spring.The simplest way to retrieve the currently authenticated principal is via a static call to the SecurityContextHolder like this :
Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
String username = authentication.getName();
So you can refactor you method getAllPresentations() in service class to accept username as argument, and then you can load user by passed username and return presentations for that user.

Answer 2

One way to do what you want is to use #PostFilter annotation to filter List<Presentation> that the authenticated user owns or if the authenticated user has a role ADMIN like this:
#GetMapping
#PostFilter("filterObject.user.username == authentication.principal.username or hasRole('ADMIN')")
public List<PresentationDTO> getAllPresentations() {
return presentationService.getAllPresentations();
}