Different ways to get AEM admin session

Method 1: 

AEM admin session can be obtained using below method but this is deprecated

@Reference private SlingRepository repository; adminSession = repository.loginAdministrative(null);
Method 2: 

Another way to get the session (not the recommended way)
Session session = repository.login(new SimpleCredentials("admin", "admin".toCharArray()),"crx.default");

Method 3: 

@Reference 

public ResourceResolverFactory rrFactory; 

ResourceResolver adminResolver = rrFactory.getAdministrativeResourceResolver(null); 

Session adminSession = adminResolver.adaptTo(Session.class);
Method 4: 

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);

            session = resolver.adaptTo(Session.class);

           }

See Community Article

Method 5:
You can create a user and assign it to the administrative group and use its credentials rather than the default admin user.
You may also want to take a look at this article which goes over using the correct resource resolver in AEM 6.