public class RestStateRelay

A StateRelay over your own HTTPS endpoint, which is all most applications need.

Continuity.setRelay(new RestStateRelay("https://api.example.com/continuity") {
    protected String getToken() {
        return session.getAccessToken();
    }
 });

The contract

Two requests against the one URL you supply:

• POST with the state as a JSON body and Content-Type: application/json. Store it against the signed-in user, replacing whatever you held for them. Any 2xx means stored.
• GET, answering with the newest state you hold for that user as the same JSON, or an empty body when you hold none. A 404 also means none.

The JSON is exactly what StateCodec.toJson(AppState) produces, and it is a closed shape: your endpoint stores and returns the document, and never needs to look inside it.

Identity is yours

Which states belong to the same person is the one question the framework cannot answer, which is why the token comes from getToken() rather than from a constructor: it is read at each request, so a session that refreshes its token is followed automatically. Return null for an endpoint that identifies the user some other way – a cookie, mutual TLS – and the header is simply omitted.

Threading

Both methods are called from a background thread and block, which is what the framework expects of a relay. getToken() is called on that same thread, so it must not wait on the event dispatch thread.