My app is supposed to call a URL which would provide simple text data (1 or 0). The URL can be http/https and method is POST.
For example, my java app will call https://web.address.com:1234/isActive with some request parameter and then this URL would simply return 0 or 1 in text format.
What lightweight API should I use? Or can I use Play Framework's WS API only (not the whole framework)?
For this "simple" task you can use Java's URL and URLConnection classes from the standard library which are capable of connecting to a remote server and perform basic HTTP operations. Also know that URL.openConnection() returns an HttpURLConnection instance with many helper/utility methods and constants regarding HTTP protocol.
Also see this excellent post which provides you more details and examples including performing an HTTP POST operation:
Using java.net.URLConnection to fire and handle HTTP requests
If you don't want to "do-it-yourself", there are numerous 3rd party libraries availabe (google it). To mention a few:
Apache HttpComponents (former Apache HttpClient)
