UserService { public boolean can(ByteBuffer username, Permission permission, String environment) { lock.readLock().lock(); try { Role role = getRole(username); if(role == Role.SERVICE || role == Role.ADMIN) { return true; } else { User user = getUserStrict(username); return user.can(permission, environment); } } finally { lock.readLock().unlock(); } } @SuppressWarnings("unchecked") private  UserService(String backingStore, int accessTokenTtl,
            TimeUnit accessTokenTtlUnit); static UserService create(String backingStore); boolean authenticate(ByteBuffer username, ByteBuffer password); boolean can(ByteBuffer username, Permission permission,
            String environment); void create(ByteBuffer username, ByteBuffer password, Role role); void delete(ByteBuffer username); void disable(ByteBuffer username); void enable(ByteBuffer username); boolean exists(ByteBuffer username); void forEachUser(Consumer<ByteBuffer> consumer); Role getRole(ByteBuffer username); void grant(ByteBuffer username, Permission permission,
            String environment); boolean isEnabled(ByteBuffer username); void revoke(ByteBuffer username, String environment); void setPassword(ByteBuffer username, ByteBuffer password); void setRole(ByteBuffer username, Role role); final AccessTokenManager tokens; }
@Test public void testServiceUserAlwaysHasPermission() { ByteBuffer username = service.tokens .identify(service.tokens.serviceIssue()); Assert.assertTrue(service.can(username, Permission.READ, Random.getSimpleString())); Assert.assertTrue(service.can(username, Permission.WRITE, Random.getSimpleString())); }