docs: public void init(ServletConfig config) throws ServletException {
          super.init(config);
          this.engine = initTemplateEngine(config);
          if (engine == null) {
              throw new ServletException("Template engine not instantiated.");
          }
          String value = config.getInitParameter("generated.by");
          if (value != null) {
              this.generateBy = Boolean.valueOf(value);
          }
          value = config.getInitParameter(GROOVY_SOURCE_ENCODING);
          if (value != null) {
              this.fileEncodingParamVal = value;
          }
          log("Servlet " + getClass().getName() + " initialized on " + engine.getClass());
      }