現在、サーブレット (アプリ サーバー グラスフィッシュ) に基づいてアプリケーションを実行しています。外部アプリケーションは、そのサーブレットに対して HTTP 呼び出しを行い、その設計目的が正常に達成されると応答を取得します。
アプリケーション全体を JSF2.0 に移行する必要があります。これにはフロント エンドが必要であり、サーブレット/jsp に固執することはオプションではありません。
私の質問は次のとおりです。
What's the recommended way to achieve the scenario of external applications getting things done through http calls in my JSF2.0 web app (that is currently I am achieving with servlets)
Like BalusC said, JSF is not exactly what you need and is not designed for what you intend to use it for, webservices are. That being said, you could achieve your goals using JSF if developing an effective web service is not in the cards for you ,either because of a lack of technical expertise on your team or the time factor or other technical constraints require you to serve your customers via a webapp (I honestly can't think of any but hey, you never know)
That being said, I'm assuming you already know your way around JSF2: take a look at this answer to a question somewhat similar to yours. Ultimately, since you're in the Java EE 5-6 stack, I'd strongly suggest you begin work on developing webservices (for basic requirements,they're fairly straightforward to develop). You can download a tutorial here or use oracle's tutorial
I need to maintain some counters in Application scope; Would you advise me to keep using servlets in my jsf app too and are the application scoped beans callable in servlets?
Unless you give us your specific use case, there are very few and far between reasons maintain a servlet within a JSF app. Yes, application,session and request scoped beans are accessible from within a servlet. They're simply stored as objects within the scopes they're named for, application scoped beans within the applicationScope, session scoped beans within the session and request scoped beans within the request. You may use your JSF webapp to serve low level http requests, but it's a square peg in a round hole chief.
あなたが古いアプリケーションを説明した方法は、Web サービスのように聞こえます。
JSF はコンポーネント ベースの MVC フレームワークであり、Web サービス フレームワークではありません。したがって、JSF は基本的にこの仕事には不適切なツールです。標準の Java EE スタックを引き続き使用する場合は、代わりにJAX-WS (SOAP) またはJAX-RS (RESTful) を検討してください。後者は、最近の「標準的な」Web サービス フレームワークです。