protected ViewResolver getViewResolver(final String theme) {
        if (resolvers.containsKey(theme)) {
            return resolvers.get(theme);
        }
        val resolver = viewResolverFactory.create(theme);
        resolvers.put(theme, resolver);
        return resolver;
    }
Get (or create) the view resolver for the theme.

@param theme the theme
@return the view resolver
support/cas-server-support-thymeleaf-core/src/main/java/org/apereo/cas/services/web/ThemeBasedViewResolver.java