How to set UnmodifiableRandomAccessList to Set<Object> in java

Question

There is an Oauth2Authentication object that contains user-authority. When I want to get its authority and set it in authority of User object like this:

OAuth2Authentication oAuth2Authentication = (OAuth2Authentication) SecurityContextHolder.getContext().getAuthentication();

LinkedHashMap linkedHashMap = (LinkedHashMap) oAuth2Authentication.getUserAuthentication().getDetails();


user.setAuthorities((Set<GrantedAuthority>) oAuth2Authentication.getAuthorities());

the following exception is raised:

java.lang.ClassCastException: java.util.Collections$UnmodifiableRandomAccessList cannot be cast to java.util.Set

How do I fix it?

Note:
The type of Authorities of User object is Set<GrantedAuthority>

Answer 1

If oAuth2Authentication.getAuthorities() is a List, you can easily create a Set from it:

user.setAuthorities(new HashSet<GrantedAuthority>(oAuth2Authentication.getAuthorities()));

Note that GrantedAuthority should have a proper implementation of hashCode() and equals() in order to be used as a member of a HashSet.