java后台调用JS代码判断浏览器版本是否低于IE9，低版本跳转不同页面

ScriptEngineManager manager = new ScriptEngineManager();
     ScriptEngine engine = manager.getEngineByName("javascript");
     
     engine.eval("function isLtIE9(userAgent) {" 
       +"print('userAgent:'+userAgent);"
        +"var reIE = false;"
       +"if(userAgent.indexOf('compatible') > -1 && userAgent.indexOf('MSIE') > -1 && !(userAgent.indexOf('Opera') > -1)) {"        
        +"var regStr_ie = /MSIE [\\d.]+/;"
        +"var regStr_version = /[\\d.]+/;"
        +"var verson = new RegExp(regStr_version);"
        +"reIE = new RegExp(regStr_ie);"
              +"reIE.test(userAgent);"         
              +"var IEVersion = userAgent.match(reIE).toString();"        
        +"IEVersion =  parseFloat(IEVersion.match(verson));"             
              +"reIE = IEVersion < 9 ? true : false;"
       +"}"
       +"return reIE;"
      +"}");
     if(engine instanceof Invocable){
      Invocable invocable = (Invocable) engine;
      Boolean flag = (Boolean) invocable.invokeFunction("isLtIE9",ua);
      //System.out.println("invocable.invokeFunction('isLtIE9',ua): "+invocable.invokeFunction("isLtIE9",ua).getClass());
      System.out.println("flag: "+flag);
      if(flag){
       response.sendRedirect("/car/userLogin/ieapply");
      }else{
       response.sendRedirect("/car/userLogin/index");
      }
     }