PackageCreatorController.cls

@RemoteAction
global static ResponseWrapper savePackageInCache(String jsonString, String uniqueKey)
{
    ResponseWrapper wrap = new ResponseWrapper();
    try 
    {
        String base64Str = EncodingUtil.base64Encode(Blob.valueOf(jsonString));
        Datetime currentTime = System.now();
        String timeStr = ''+currentTime.Year()+currentTime.Month()+currentTime.Day()
                        +currentTime.Hour()+currentTime.Minute()+currentTime.Second();
        if(String.isBlank(uniqueKey))
        {
            uniqueKey = UserInfo.getUserId()+timeStr;
        }
        System.debug('base64Str'+base64Str);
        Cache.Org.put('local.PackageXMLStorage.'+uniqueKey, base64Str);
        wrap.uniqueKey = uniqueKey;
        wrap.isSuccess = true;
    }
    catch (Exception e) {
        wrap.isSuccess = false;
        wrap.errorMsg = e.getMessage();
    }
    return wrap;
}