retrieve resourceresolver as logged in user

Hi

how do we retrieve resourceresolver on behalf of logged in user? in this case, am getting anonymous as value when getUserID() method is called. Also, what's the difference when we retrieve resource resolver via getResourceResolver(userInfo) and getThreadResourceResolver(). From the logs seems like they both reference to same resolver object instance and no difference in log values.

Map<String,Object> userInfo = new HashMap<String, Object>();

userInfo.put(ResourceResolverFactory.SUBSERVICE, "myuser");

ResourceResolver resourceResolver = resourceFactory.getResourceResolver(userInfo);

ResourceResolver resourceResolverCurrentThread = resourceFactory.getThreadResourceResolver();

logger.info("resource resolver {}",resourceResolver.toString());

logger.info("resource resolver {}",resourceResolver.getUserID());

logger.info("resource resolver {}",resourceResolver.isLive());

logger.info("thread resource resolver {}",resourceResolverCurrentThread.toString());

logger.info("thread resource resolver {}",resourceResolver.getUserID());

logger.info("thread resource resolver {}",resourceResolver.isLive());