public interface StateRelay

Known subtypesRestStateRelay

Carries state between devices the platform will not carry it between – an iPhone and an Android tablet, two devices that are never in the same room, a phone and the web build.

Codename One ships no server for this. A relay is the application’s own endpoint, which is also the only honest arrangement: the relay has to know which states belong to the same person, and that is the app’s account system, not the framework’s. RestStateRelay covers the common case over HTTPS; implement this interface directly for anything else.

Both methods are called from a background thread and may block. Neither is called on the event dispatch thread, so ordinary blocking com.codename1.io code is correct here.

Methods

`public abstract void publish(AppState state) throws IOException`	Sends a state.
`public abstract` `AppState fetch() throws IOException`	Asks for the newest state this user has on any device.

Method details

publish

public abstract void publish(AppState state)
throws IOException

Sends a state. Called after each checkpoint, so implementations that talk to a slow endpoint should coalesce rather than send every one.

Parameters

state AppState: the state to send

Throws

java.io.IOException: when the send failed. The framework logs it and keeps the state, which the next checkpoint’s publisher sends – unless a newer state has superseded it by then, or the user signed out in between. It is not retried on a timer: one attempt per change beats spinning against an endpoint that is down.

fetch

public abstract AppState fetch()
throws IOException

Asks for the newest state this user has on any device. Returning this device’s own most recent state is fine and expected – the framework recognizes its own echo by device id and sequence, and ignores it.

Returns

the state, or null when the endpoint has nothing

Throws

java.io.IOException: when the fetch failed