@hitachivantara/app-shell-services

Hitachi Vantara App Shell Services. Support package to manage services at the App Shell ecosystem.

Overview

This package provides service management capabilities including:

- Service registration and resolution
- React hooks for service consumption
- Type-safe service interfaces

Usage

Services supports a consumer/provider model where:

- Consumers, like an app owning a header action for example, will consume a given service _contract_ either from the shared-services package from other app or, if also a provider, its own shared-services package. The services are identified by an id that, ideally, should be unique while also providing information about the type it expects like main-app:AppsMetadata. This way, the consumers know the type they expect and the providers know what to implement, without collisions in the multi-tenant App Shell ecosystem.
- Providers implement services that match the consumer's contract and register them under the consumer's id in its app-shell.config.ts file as example below:

``typescript
services: {
"@some-package/main-app-services:AppsMetadata": [{
instance: {
value: {
name: "dummy app",
description: "This is 'dummy app' description",
version: 2.0,
final: false,
}
}
}],
}
`

This way, looking at the configuration, it is clear that there is a consumer application (main-app) that expects service-providers to implement the AppsMetadata contract and register them under its @some-package/main-app-services:AppsMetadata service definition, keeping the consumer resilient: as long as service-providers adhere to the declared contract the consumer code will not break.

Example (consumer)

Exploring the example above, the consumer should register the service contract and definition in a package that can be shared between the consumer and the provider:

`typescript
// @some-package/main-app-services
export type AppsMetadata = {
appId: string;
appName: string;
version: number;
isRelease: boolean;
};

/**
* Service definitions that the consumer 'main app' exposes on a services shared package.
*/
export const MainAppServiceDefinitions = {
/**
* The {@const AppsMetadata} service represents the service-provider application metadata.
*
* The service-providers that implement this contract will have its implementation displayed on a page.
*
* Instances of this service are typescript constants of type {@link AppsMetadata}.
*/
AppsMetadata: {
id: "@some-package/main-app-services:AppsMetadata",
},
};
`

The main app consumes all the service definitions under its identifier using the useServices hook, which returns all the successfully loaded services of the requested identifier, namely the MainAppServiceDefinitions.AppsMetadata service definition.
This way, as long as any provider implements and registers a service that matches the AppsMetadata contract, it will be safe to render as expected:

`typescript
const AboutApps: FC = () => {
const { services: appsMetadata[], isPending, error } = useServices(
ServiceDefinitions.AppsMetadata.id,
);

if (isPending) {
return Loading apps metadata from services...;
}

if (error) {
const errorMessage = Failed to apps metadata: ${ServiceDefinitions.AppsMetadata.id};
return {errorMessage};
}

return (

Applications information

{appsMetadata.map((metadata, index) => {
return (


Application: {metadata.appName}


{metadata.version} - {metadata.isRelease ? "Release" : "In development"}


);
})}


);
};
`

Example (provider)

A simple way to implement a service-provider that matches the AppsMetadata contract is a constant like below:

`typescript
import { AppsMetadata } from "@some-package/main-app-services";

const dummyAppMetadata: AppsMetadata = {
appId: "ProviderApp",
appName: "A provider app",
version: 1.0,
isRelease: true,
};
`

and having it registered on its app-shell.config.ts file, under the consumer service identifier.

`typescript
//...
services: {
"@some-package/main-app-services:AppsMetadata": [
{
instance: {
bundle: "dummy-app/metadata/dummyAppMetadata.js",
},
ranking: 100,
}
],
},
//...
`

$3

To see more examples, please check the Default App ServicesDemo page and the app-shell.config.ts file.

Installation

The App Shell Services is available as an NPM package, and can be installed with:

`bash
npm install @hitachivantara/app-shell-services
``