What is the best way to get the ResourceResolver in AEM6.1

IN AEM 6.1 -- you need an AEM system user -- see this community article: 

https://helpx.adobe.com/experience-manager/using/jqom.html

It shows you how to setup the system user and properly run this code:

Map<String, Object> param = new HashMap<String, Object>();
        param.put(ResourceResolverFactory.SUBSERVICE, "jqom");
        ResourceResolver resolver = null;
          
        try {
                     
            //Invoke the getServiceResourceResolver method to create a Session instance
            resolver = resolverFactory.getServiceResourceResolver(param);