code: private FilterInstanceWrapper loadFilter(String filterName) throws ServletException {
          ClassLoader origClassLoader = ThreadContextHelper.getContextClassLoader();
          try {
              final ClassLoader warClassLoader = webApp.getClassLoader();
              if (warClassLoader != origClassLoader) {
                  ThreadContextHelper.setClassLoader(warClassLoader);
              }
              // initialize the filter instance wrapper
              return _loadFilter(filterName);
          } finally {
              ThreadContextHelper.setClassLoader(origClassLoader);
          }
      }
docs: Creates a new FilterInstanceWrapper object corresponding to the passed in
  filter name. This new object is added to the _filterWrappers hash table
  
  @param filterName
  - String containing the name of the filter inst to create
  
  @return a FilterInstanceWrapper object corresponding to the passed in
  filter name
  
  @throws ServletException