Interface ActivatorCapability

An activator allows a micro application to initialize and connect to the platform upon host application's startup, i.e., when the user loads the web application into the browser.

In the broadest sense, an activator is a kind of microfrontend, i.e. an HTML page that runs in an iframe. In contrast to regular microfrontends, however, at platform startup, the platform loads activator microfrontends into hidden iframes for the entire platform lifecycle, thus, providing a stateful session to the micro application on the client-side.

Some typical use cases for activators are receiving messages and intents, preloading data, or flexibly providing capabilities.

A micro application registers an activator as public activator capability in its manifest, as follows:

"capabilities": [
  {
    "type": "activator",
    "private": false,
    "properties": {
      "path": "path/to/the/activator"
    }
  }
]
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Activation Context

An activator's microfrontend runs inside an activation context. The context provides access to the activator capability, allowing to read properties declared on the activator capability.

You can obtain the activation context using the ContextService as following.

// Looks up the activation context.
const ctx: ActivationContext = await Beans.get(ContextService).lookup(ACTIVATION_CONTEXT);
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Multiple Activators

A micro application can register multiple activators. Note, that each activator boots the micro application on its own and runs in a separate browsing context. The platform nominates one activator of each micro application as its primary activator. The nomination has no relevance to the platform but can help code decide whether to install singleton functionality.

You can test if running in the primary activation context as following.

// Looks up the activation context.
const ctx = await Beans.get(ContextService).lookup<ActivationContext>(ACTIVATION_CONTEXT);
// Checks if running in the context of the primary activator.
const isPrimary: boolean = ctx.primary;
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Sharing State

Since an activator runs in a separate browsing context, microfrontends cannot directly access its state. Instead, an activator could put data, for example, into session storage, so that microfrontends of its micro application can access it. Alternatively, an activator could install a message listener, allowing microfrontends to request data via client-side messaging.