docs: public FilterInstanceWrapper getFilterInstanceWrapper(String filterName) throws ServletException {
          if (com.ibm.ejs.ras.TraceComponent.isAnyTracingEnabled() && logger.isLoggable(Level.FINE))
              logger.entering(CLASS_NAME,"getFilterInstanceWrapper", "entry for " + filterName);
  
          try {
              FilterInstanceWrapper filterInstW;
  
              // see if the filter is already loaded
  
              filterInstW = (FilterInstanceWrapper) (_filterWrappers.get(filterName));
              if (filterInstW == null) { //PM01682 Start
                  synchronized(webAppConfig.getFilterInfo(filterName)){
                      // may be more are waiting for lock, check and see if the filter is already loaded
                      filterInstW = (FilterInstanceWrapper) (_filterWrappers.get(filterName));
                      if (filterInstW == null) {
                          // filter not loaded yet...create an instance wrapper
                          filterInstW = loadFilter(filterName);
                      }
                  }//PM01682 End
              }
              if (com.ibm.ejs.ras.TraceComponent.isAnyTracingEnabled()&&logger.isLoggable (Level.FINE)) {
                  logger.exiting(CLASS_NAME,"getFilterInstanceWrapper", "exit for " + filterName);
              }
              return filterInstW;
          } catch (ServletException e) {
              // logServletError(filterName,
              // nls.getString("Failed.to.load.filter","Failed to load filter"),
              // e);
              com.ibm.wsspi.webcontainer.util.FFDCWrapper.processException(e,
                                                                           "com.ibm.ws.webcontainer.filter.WebAppFilterManager.getFilterInstanceWrapper", "166", this);
              throw e;
          } catch (Throwable th) {
              // logServletError(filterName,
              // nls.getString("Failed.to.load.filter","Failed to load filter"),
              // th);
              com.ibm.wsspi.webcontainer.util.FFDCWrapper.processException(th,
                                                                           "com.ibm.ws.webcontainer.filter.WebAppFilterManager.getFilterInstanceWrapper", "172", this);
              throw new ServletException(MessageFormat.format("Filter [{0}]: could not be loaded", new Object[] { filterName }), th);
          }
  
      }