docs: private List<Class<?>> getListenerInterfaces() {
          List<Class<?>> listenerInterfaces = 
              new ArrayList<Class<?>>(Arrays.asList(SERVLET30_LISTENER_INTERFACES));            
  
          // Condition the HTTP ID Listener on Servlet 3.1 enablement.
      
          if (com.ibm.ws.webcontainer.osgi.WebContainer.getServletContainerSpecLevel() <
              com.ibm.ws.webcontainer.osgi.WebContainer.SPEC_LEVEL_31) {
              return listenerInterfaces;
          }
  
          // Use reflection for referenced Servlet 3.1 classes.  Those won't load unless
          // Servlet 3.1 is enabled.
              
          Class<?> httpIDListenerInterface;           
          
          try {
              httpIDListenerInterface = Class.forName(HTTP_ID_LISTENER_CLASS_NAME);
          } catch (ClassNotFoundException e) {
              httpIDListenerInterface = null;
          }
              
          if (httpIDListenerInterface != null) {
              listenerInterfaces.add(httpIDListenerInterface);
          } else {
              if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
                  Tr.debug(tc, "Servlet 3.1 is enabled but failed to find the HTTP ID Listener class [ " + HTTP_ID_LISTENER_CLASS_NAME + " ]");
              }
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isDebugEnabled()) {
              Tr.debug(tc, "Supported listener interfaces: " + listenerInterfaces);
          }
                 
          return listenerInterfaces;                
      }