code: public boolean putFilter(File file) throws Exception
      {
          try {
              String sName = file.getAbsolutePath();
              if (filterClassLastModified.get(sName) != null && (file.lastModified() != filterClassLastModified.get(sName))) {
                  LOG.debug("reloading filter " + sName);
                  filterRegistry.remove(sName);
              }
              ZuulFilter filter = filterRegistry.get(sName);
              if (filter == null) {
                  Class clazz = compiler.compile(file);
                  if (!Modifier.isAbstract(clazz.getModifiers())) {
                      filter = filterFactory.newInstance(clazz);
                      putFilter(sName, filter, file.lastModified());
                      return true;
                  }
              }
          }
          catch (Exception e) {
              LOG.error("Error loading filter! Continuing. file=" + String.valueOf(file), e);
              return false;
          }
  
          return false;
      }
docs: From a file this will read the ZuulFilter source code, compile it, and add it to the list of current filters
  a true response means that it was successful.
  
  @param file
  @return true if the filter in file successfully read, compiled, verified and added to Zuul
  @throws IllegalAccessException
  @throws InstantiationException
  @throws IOException