How to use

isSingletonBinding

method

in

com.google.inject.servlet.ServletScopes

if (!isSingletonBinding(injector.getBinding(servletKey))) {
 throw new ServletException("Servlets must be bound as singletons. "
  + servletKey + " was not bound in singleton scope.");

if (!isSingletonBinding(injector.getBinding(filterKey))) {
 throw new ServletException("Filters must be bound as singletons. "
  + filterKey + " was not bound in singleton scope.");