code: public SessionProvider getSessionProvider(Object key)
     {
        if (providers.containsKey(key))
        {
           return providers.get(key);
        }
        else
        {
           throw new IllegalArgumentException("SessionProvider is not initialized");
        }
     }
docs: /*
  (non-Javadoc)
  @see
  org.exoplatform.services.jcr.ext.app.SessionProviderService#getSessionProvider(java.lang.Object
  )