Spring Security：登录后更改权限

Question

我试图更改当前登录用户的权限，但我无法使其正常工作。

我关注这篇文章（在底部，OP声称找到了解决方案）：http://forum.spring.io/forum/spring-projects/security/60663-change-user-logged-authorities-on-the-fly

我的UserDetails :: getAuthorities的实现根据用户的内部状态生成权限集合，并返回它（我不使用属性来保存它）：

@Override
public Collection<? extends GrantedAuthority> getAuthorities() {
    Collection<GrantedAuthority> authorities = new ArrayList<GrantedAuthority>();

    if (... some condition ...) {
        authorities.add(new SimpleGrantedAuthority("ROLE_A"));
    } else {
        authorities.add(new SimpleGrantedAuthority("ROLE_B"));
    }

    return authorities;
}

我刷新权限的代码：

System.out.println(SecurityContextHolder.getContext().getAuthentication().getAuthorities());

SecurityContext context = SecurityContextHolder.getContext();
Authentication authentication = context.getAuthentication();

UserDetails user = userDetailsService.loadUserByUsername("john.doe@example.com");
UsernamePasswordAuthenticationToken newAuthentication = new UsernamePasswordAuthenticationToken(user, null, user.getAuthorities());

context.setAuthentication(newAuthentication);
SecurityContextHolder.setContext(context);

System.out.println(SecurityContextHolder.getContext().getAuthentication().getAuthorities());

控制台输出（这是预期的）：

[ROLE_A]
[ROLE_B]

问题：新权限不会保留。当我稍后调用服务时，权限是[ROLE_A]，而不是[ROLE_B]。