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 it's 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.