Data Sharing

A shared context object is a Map containing cross app data. You can access all available context objects in order to manipulate them:

Collection<String> names = io.contexts().names();

To subscribe for shared context updates, use the io.contexts().subscribe() call, passing the name of the desired context object:

io.contexts().subscribe("app-styling")
                .thenAccept(context -> context.data(data -> {
            // use context data here
        }));

If the specified shared context object doesn't exist, it will be created. In the example above, the changes to the context object can be handled in the context.data(data -> {}) callback.

You can also update a shared context object by using io.contexts().update() and passing as a first argument the name of the context object you want to update, and as a second - a Map<String, Object> with the delta values:

io.contexts().update("app-styling", Collections.singletonMap("backgroundColor", "red"));

If the key you pass in the Map object exists in the shared context object, it will be overwritten with the new value. If it doesn't exist, it will be created. If the value of a key in the Map you pass to io.contexts().update() is null, then that key will be deleted from the shared context object.

Let's say you have subscribed to a shared context named "app-styling", which already has two entries - "backgroundColor", "red" and "alternativeColor", "yellow". In the example below:

• "backgroundColor" will be overwritten with a new value - "blue";
• "alternativeColor" will be deleted from the shared context object;
• "borderColor" will be created as a new key in the shared context object and its value will be set to "grey";

io.contexts()
        .subscribe("app-styling")
        .thenAccept(context -> {
            context.data(data -> {
                // use context data here
            });

            Map<String, Object> delta = new HashMap<>();
            delta.put("backgroundColor", "blue");
            delta.put("alternativeColor", null);
            delta.put("borderColor", "grey");

            context.update(delta);
        });