Service Proxies

Calling a REST endpoint from Angular applications is common. We usually create services matching server-side controllers and interfaces matching DTOs to interact with the server. This often results in manually transforming C# code into TypeScript equivalents and that is unfortunate, if not intolerable.

To avoid manual effort, we might use a tool like NSWAG that generates service proxies. However, NSWAG has some disadvantages:

• It generates a single .ts file which gets too large as your application grows. Also, this single file does not fit the modular approach of ABP.
• To be honest, the generated code is a bit ugly. We would like to produce code that looks as if someone wrote it.
• Since swagger.json does not reflect the exact method signature of backend services, NSWAG cannot reflect them on the client-side as well.

ABP introduces an endpoint that exposes server-side method contracts. When the generate-proxy command is run, ABP CLI makes an HTTP request to this endpoint and generates better-aligned client proxies in TypeScript. It organizes folders according to namespaces, adds barrel exports, and reflects method signatures in Angular services.

Before you start, please make sure you start the backend application with dotnet run. There is a known limitation about Visual Studio, so please do not run the project using its built-in web server.

Run the following command in the root folder of the angular application:

abp generate-proxy -t ng

The command without any parameters creates proxies only for your own application's services and places them in your default Angular application. There are several parameters you may use to modify this behavior. See the CLI documentation for details.

The generated files will be placed in a folder called proxy at the root of the target project.

Each folder will have models, enums, and services defined at related namespace accompanied by a barrel export, i.e. an index.ts file for easier imports.

The command can find application/library roots by reading the angular.json file. Make sure you have either defined your target project as the defaultProject or pass the --target parameter to the command. This also means that you may have a monorepo workspace.

Angular Project Configuration

If you've created your project with version 3.1 or later, you can skip this part since it will be already installed in your solution.

For a solution that was created before v3.1, follow the steps below to configure your Angular application:

1. Add @abp/ng.schematics package to the devDependencies of the Angular project. Run the following command in the root folder of the angular application:

npm install @abp/ng.schematics -D

2. Add rootNamespace property to the /src/environments/environment.ts in your application project as shown below. MyCompanyName.MyProjectName should be replaced by the root namespace of your .NET project.

export const environment: Config.Environment = {
  // other environment variables...
  apis: {
    default: {
      rootNamespace: "MyCompanyName.MyProjectName",
      // other environment variables...
    },
  },
};

3. [OPTIONAL] Add the following paths to tsconfig.base.json in order to have a shortcut for importing proxies:

{
  // other TS configuration...
  "compilerOptions": {
    // other TS configuration...
    "paths": {
      "@proxy": ["src/app/proxy/index.ts"],
      "@proxy/*": ["src/app/proxy/*"]
    }
  }
}

The destination the proxy folder is created and the paths above may change based on your project structure.

Services

The generate-proxy command generates one service per back-end controller and a method (property with a function value actually) for each action in the controller. These methods call backend APIs via RestService.

A variable named apiName (available as of v2.4) is defined in each service. apiName matches the module's RemoteServiceName. This variable passes to the RestService as a parameter at each request. If there is no microservice API defined in the environment, RestService uses the default. See getting a specific API endpoint from application config

The providedIn property of the services is defined as 'root'. Therefore there is no need to provide them in a module. You can use them directly by injecting them into the constructor as shown below:

import { BookService } from '@proxy/books';

@Component(/* component metadata here */)
export class BookComponent implements OnInit {
  constructor(private service: BookService) {}

  ngOnInit() {
    this.service.get().subscribe(
      // do something with the response
    );
  }
}

The Angular compiler removes the services that have not been injected anywhere from the final output. See the tree-shakable providers documentation.

Models

The generate-proxy command generates interfaces matching DTOs in the back-end. There are also a few core DTOs in the @abp/ng.core package. In combination, these models can be used to reflect the APIs.

import { PagedResultDto } from "@abp/ng.core";
import { BookDto } from "@proxy/books";

@Component(/* component metadata here */)
export class BookComponent implements OnInit {
  data: PagedResultDto<BookDto> = {
    items: [],
    totalCount: 0,
  };
}

Enums

Enums have always been difficult to populate in the frontend. The generate-proxy command generates enums in a separate file and exports a ready-to-use "options constant" from the same file. So you can import them as follows:

import { bookGenreOptions } from "@proxy/books";

@Component(/* component metadata here */)
export class BookComponent implements OnInit {
  genres = bookGenreOptions;
}

...and consume the options in the template as follows:

<!-- simplified for sake of clarity -->
<select formControlName="genre">
  <option [ngValue]="null">Select a genre</option>
  <option *ngFor="let genre of genres" [ngValue]="genre.value">
    {{ genre.key }}
  </option>
</select>

Please see this article to learn more about service proxies.

Known Limitations

When you run a project on Visual Studio using IIS Express as the web server, there will be no remote access to your endpoints. This is the default behavior of IIS Express since it explicitly protects you from the security risks of running over the network. However, that will cause the proxy generator to fail because it needs a response from the /api/abp/api-definition endpoint. You may serve your endpoints via Kestrel to avoid this. Running dotnet run in your command line (at your project folder) will do that for you.