Advanced implementation of Licensing Validation in angular applications.

Licensing validation is any application's most important feature, allowing only authorized users to access its functionalities. In an Angular application, the licensing validation normally takes place by the following:

1. The Angular app is loaded.
2. The licensing information is fetched from a backend API or local storage.
3. The licensing data is validated.

That does the job but there's more grace in doing a license check without loading up the Angular application first. Using what's called an AppInitializer in Angular.

What is AppInitializer in Angular?

The AppInitializer is a special Angular provider for running some code before Angular has fully initialized the application. It's used everywhere when one needs for example:

• Loading settings.
• Services initialization.

We can use AppInitializer for license validation so that the application checks for a license before it loads up, adding to both security and user experience.

How to Use AppInitializer for Licensing Validation in Angular

Here's how you can validate licensing using AppInitializer in Angular:

1. Create a License Service

The logic for validation will be carried out by the license service. This may call a license data from the local storage or from an external server. The implementation may look like this.

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable({
  providedIn: 'root'
})
export class LicenseService {
  constructor(private http: HttpClient) {}

  validateLicense(): Observable<boolean> {
this.licenseService.validateLicense('/api/validate-license').subscribe(
  success => {
    if (!success) {
      alert('Invalid License!');
      // You can redirect or stop the app from initializing
    }
  },
  error => {
    alert('License validation failed!');
  }
);
  }
}

1. Implement the AppInitializer Function The AppInitializer function will make sure to validate the license before the app starts. It calls the LicenseService's validateLicense method and waits for the result.

import { LicenseService } from './license.service';
import { APP_INITIALIZER } from '@angular/core';

export function licenseInitializer(licenseService: LicenseService) {
  return () => {
    return licenseService.validateLicense().toPromise().catch(() => {
      alert('Invalid or missing license!');
      // Handle invalid license (e.g., redirect or block app initialization)
      return Promise.reject();
    });
  };
}

3. Provide the AppInitializer in the AppModule

By providing APP_INITIALIZER in the AppModule, the app will wait for the license validation to complete before proceeding to load.

import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { AppComponent } from './app.component';
import { LicenseService } from './license.service';
import { licenseInitializer } from './app-initializer';
import { HttpClientModule } from '@angular/common/http';

@NgModule({
  declarations: [AppComponent],
  imports: [BrowserModule, HttpClientModule],
  providers: [
    {
      provide: APP_INITIALIZER,
      useFactory: licenseInitializer,
      deps: [LicenseService],
      multi: true
    }
  ],
  bootstrap: [AppComponent]
})
export class AppModule {}

4. Handle Invalid License

In the case of an invalid license or no license, the AppInitializer can prevent the app from loading and inform the user. You may want to show an alert or navigate the user to a license activation page.

Why AppInitializer for Licensing?

Using AppInitializer to validate licenses has several advantages:

• Avoids Unauthorized Access: Because the app will only load if the license is valid.
• Enhanced Security: The validation occurs before any application logic is executed.
• Enhanced User Experience: Provides appropriate messaging for invalid licenses without partially loading the app.
• Centralized Logic: All initialization tasks, including licensing, can be handled in a clean and organized manner.

Conclusion

AppInitializer in Angular provides a very handy way to perform some crucial operations before the application is fully loaded. It can be combined with license validation to further increase the security, reliability, and user experience of your application. The approach will provide you with certainty that only valid users will access your application's features, which equals peace of mind for both you and the users.