NodeTSkeleton, a Clean Architecture template project for NodeJs

NodeTskeleton is a Clean Architecture based template project for NodeJs using TypeScript to implement with any web server framework or even any user interface.

The main philosophy of NodeTskeleton is that your solution (domain and application, “business logic”) should be independent of the framework you use, therefore your code should NOT BE COUPLED to a specific framework or library, it should work in any framework.

The design of NodeTskeleton is based in Clean Architecture, an architecture that allows you to decouple the dependencies of your solution, even without the need to think about the type of database, providers or services, the framework, libraries or any other dependencies.

NodeTskeleton has the minimum tools necessary for you to develop the domain of your application, you can even decide not to use its included tools (you can remove them), and use the libraries or packages of your choice.

Philosophy 🧘🏽

Applications are generally developed to be used by people, so people should be the focus of them.

For this reason user stories are written, stories that give us information about the type of user (role), procedures that the user performs in a part of the application (module), important information that serves to structure the solution of our application, and in practice, how is this?

The user stories must be in the src/application path of our solution, there we create a directory that we will call modules and inside this, we create a directory for the task role, for example (customer, operator, seller, admin, ...) and inside the role we create a directory of the corresponding use case module, for example (product, order, account, sales, ...), and in practice that looks more or less like this:

Observations 👀

• If your application has no roles, then there's no mess, it's just modules. ;)

• But taking into consideration that if the roles are not yet defined in your application, the best option would be to follow a dynamic role strategy based on permissions and each use case within the application (or use case group) would be a specific permission that would feed the strategy of dynamic roles.

• Note that you can repeat modules between roles, because a module can be used by different roles, because if they are different roles then the use cases should also be different, otherwise those users would have the same role.

• This strategy makes the project easy to navigate, easy to change, scale and maintain, which boils down to good mental health, besides you will be able to integrate new developers to your projects in a faster way.

Included tools 🧰

NodeTskeleton includes some tools in the src/application/shared path which are described below:

Errors

Is a tool for separating controlled from uncontrolled errors and allows you to launch application errors according to your business rules, example:

throw new ApplicationError(
    resources.Get(resourceKeys.PROCESSING_DATA_CLIENT_ERROR),
    error.code || resultCodes.INTERNAL_SERVER_ERROR,
    JSON.stringify(error),
);

The function of this class will be reflected in your error handler as it will let you know when an exception was thrown by your system or by an uncontrolled error, as shown below:

return async function (err: ApplicationError, context: Context): Promise<void> {
    const result = new Result();
    if (err.name && err.name === "ApplicationError") {
        console.log("Controlled application error", err.message);
    } else {
        console.log("No controlled application error", err);
    }
};

Locals (resources)

It is a basic internationalization tool that will allow you to manage and administer the local messages of your application, even with enriched messages, for example:

import resources, { resourceKeys } from "../locals/index";

const simpleMessage = resources.Get(resourceKeys.ITEM_PRODUCT_DOES_NOT_EXIST);

const enrichedMessage = resources.GetWithParams(resourceKeys.SOME_PARAMETERS_ARE_MISSING, {
    missingParams: keysNotFound.join(", "),
});

// The contents of the local files are as follows:
/* 
// en: 
{
    ...
    "SOME_PARAMETERS_ARE_MISSING": "Some parameters are missing: {{missingParams}}.",
    "ITEM_PRODUCT_DOES_NOT_EXIST": "The item product does not exist.",
    "YOUR_OWN_NEED": "You are the user {{name}}, your last name is {{lastName}} and your age is {{age}}.",
    ...
}
// es: 
{
    ...
    "SOME_PARAMETERS_ARE_MISSING": "Faltan algunos parámetros: {{missingParams}}.",
    "ITEM_PRODUCT_DOES_NOT_EXIST": "El item del producto no existe.",
    "YOUR_OWN_NEED": "Usted es el usuario {{name}}, su apellido es {{lastName}} y su edad es {{age}}.",
    ...
}
...
*/

// You can add enriched messages according to your own needs, for example:
const yourEnrichedMessage = resources.GetWithParams(resourceKeys.YOUR_OWN_NEED, {
    name: firstName, lastName, age: userAge
});
//

And you can add all the parameters you need with as many messages in your application as required.

The resource files can be local files in JSON format or you can get them from an external service.

Mapper

The mapper is a tool that will allow us to change the entities to the DTOs within our application, including entity changes between the data model and the domain and vice versa.

This tool maps objects or arrays of objects, for example:

// For object
const textFeelingDto = this.mapper.MapObject<TextFeeling, TextFeelingDto>(
    textFeeling,
    new TextFeelingDto(),
);

// For array object
const productsDto: ProductDto[] = this.mapper.MapArray<Product, ProductDto>(
    products,
    () => this.mapper.Activator(ProductDto),
);

Activator is the function responsible for returning a new instance for each call, otherwise you would have an array with the same object repeated N times.

Result

result is a tool that helps us control the flow of our use cases and allows us to manage the response, be it an object, an array of objects, a message or an error as follows:

export class UseCaseProductGet extends BaseUseCase {
    constructor(private productQueryService: IProductQueryService) {
        super();
    }

    async Execute(idMask: string): Promise<IResult<ProductDto>> {
        // We create the instance of our type of result at the beginning of the use case.
        const result = new Result<ProductDto>();
        // With the resulting object we can control validations within other functions.
        if (!this.validator.IsValidEntry(result, { productMaskId: idMask })) {
            return result;
        }
        const product: Product = await this.productQueryService.GetByMaskId(idMask);
        if (!product) {
            // The result object helps us with the error response and the code.
            result.SetError(
                this.resources.Get(this.resourceKeys.PRODUCT_DOES_NOT_EXIST),
                this.resultCodes.NOT_FOUND,
            );
            return result;
        }
        const productDto = this.mapper.MapObject<Product, ProductDto>(product, new ProductDto());
        // The result object also helps you with the response data.
        result.SetData(productDto, this.resultCodes.SUCCESS);
        // And finally you give it back.
        return result;
    }
}

The result object may or may not have a type of response, it fits your needs.

The result object can help you in unit tests as shown below:

it("should return a 400 error if quantity is null or zero", async () => {
    itemDto.quantity = null;
    const result = await addUseCase.Execute(userUid, itemDto);
    expect(result.success).toBeFalsy();
    expect(result.error).toBe(
        resources.GetWithParams(resourceKeys.SOME_PARAMETERS_ARE_MISSING, {
            missingParams: "quantity",
        }),
    );
    expect(result.statusCode).toBe(resultCodes.BAD_REQUEST);
});

UseCase

The UseCase is a base class for extending use cases and if you were a retailer you could see it in action in the above explanation of the Result tool.

Its main function is to avoid you having to write the same code in every use case you have to build because it contains the instances of the common tools you will use in the case implementations.

The tools extended by this class are: the mapper, the validator, the message resources and their keys, and the result codes.

import validator, { Validator } from "../validator/index";
import * as resultCodes from "../result/resultCodes.json";
import resources, { resourceKeys, Resources } from "../locals/index";
import { IMap } from "../mapper/IMap";
import mapper from "../mapper";

export class BaseUseCase {
  constructor() {
    this.validator = validator;
    this.resources = resources;
    this.mapper = mapper;
  }
  mapper: IMap;
  validator: Validator;
  resources: Resources;
  resourceKeys = resourceKeys;
  resultCodes = resultCodes;
}

Or you can use the libraries from NPM directly.

import { Validator } from "validator-tsk";
import mapper, { IMap } from "mapper-tsk";
import resources, { resourceKeys, Resources } from "../locals/index";
import * as resultCodes from "../result/resultCodes.json";
/*...*/

// resources (for manage locals) and result (for application flow) are also available
import { Resources } from "resources-tsk";
import { IResult, Result, IResultT, ResultT } from "result-tsk";

Validator

The validator is a very basic but dynamic tool and with it you will be able to validate any type of object and/or parameters that your use case requires as input, and with it you will be able to return enriched messages to the client regarding the errors or necessary parameters not identified in the input requirements, for example:

/*...*/
async Execute(userUid: string, itemDto: CarItemDto): Promise<IResult<CarItemDto>> {
    const result = new Result<CarItemDto>();
    if (
        !this.validator.IsValidEntry(result, {
            User_Identifier: userUid,
            Car_Item: itemDto,
            Order_Id: itemDto?.orderId,
            Product_Detail_Id: itemDto?.productDetailId,
            Quantity: itemDto?.quantity,
        })
    ) {
        /* 
        The error message on the result object will include a base message and will add to 
        it all the parameter names that were passed on the object that do not have a valid value.
        */
        return result;
    }
    /*...*/
    return result;
}
/*...*/

Validations functions (New feature 🤩)

The validation functions extend the IsValidEntry method to inject small functions created for your own needs.

The philosophy of this tool is that it adapts to your own needs and not that you adapt to it.

To do this the IsValidEntry function input value key pair also accepts array of small functions that must perform a specific task with the parameter to be validated.

Observation

If you are going to use the validation functions feature, you must send as a parameter an array even if it is only a function.

Important note

The validation functions should return NULL if the parameter for validate is valid and a string message indicating the reason why the parameter is not valid.

// Validator functions created to meet your own needs
function ValidateEmail(email: string): string {
  if (/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(email)) {
    return null;
  }
  return resources.GetWithParams(resourceKeys.NOT_VALID_EMAIL, { email });
}

function GreaterThan(numberName: string, base: number, evaluate: number): string {
  if (evaluate && evaluate > base) {
    return null;
  }
  return resources.GetWithParams(resourceKeys.NUMBER_GREATER_THAN, {
    name: numberName,
    baseNumber: base.toString(),
  });
}

function EvenNumber(numberName: string, evaluate: number): string {
  if (evaluate && evaluate % 2 === 0) {
    return null;
  }
  return resources.GetWithParams(resourceKeys.MUST_BE_EVEN_NUMBER, {
    numberName,
  });
}


// Entry in any use case
const person = new Person("Jhon", "Doe", "[e-mail]", 21);
/*...*/
const result = new Result();
if (!validator.IsValidEntry(result, {
    Name: person.name,
    Last_Name: person.lastName,
    Email: [() => ValidateEmail(person.email)],
    Age: [
        () => GreaterThan("Age", 25, person.age),
        () => EvenNumber("Age", person.age),
    ],
})) {
    return result;
}
/*...*/
// result.error would have the following message
// "Some parameters are missing or not valid: The number Age must be greater than 25, The Age parameter should be even."

Dependency injection strategy 📦

For dependency injection, no external libraries are used. Instead, a container strategy is used in which instances and their dependencies are created and then imported into the objects where they are to be used.

This strategy is only needed in the adapter layer for controllers, services and providers, and also for the objects used in the use case tests, for example:

// In the path src/adapters/contollers/textFeeling there is a folder called container... the index file has the following:
import { UseCaseGetHighestFeelingSentence } from "../../../../application/modules/feeling/useCases/getHighest";
import { UseCaseGetLowestFeelingSentence } from "../../../../application/modules/feeling/useCases/getLowest";
import { UseCaseGetFeeling } from "../../../../application/modules/feeling/useCases/getFeeling";
import { textFeelingService } from "../../../providers/container/index";

const getFeelingTextUseCase = new UseCaseGetFeeling(textFeelingService);
const getHighestFeelingSentenceUseCase = new UseCaseGetHighestFeelingSentence(textFeelingService);
const getLowestFeelingSentenceUseCase = new UseCaseGetLowestFeelingSentence(textFeelingService);

export { getFeelingTextUseCase, getHighestFeelingSentenceUseCase, getLowestFeelingSentenceUseCase };

// The same way in src/adapters/providers there is the container folder
import TextFeelingService from "../../../application/modules/feeling/serviceContracts/textFeeling/TextFeelingService";
import TextFeelingProvider from "../../providers/feeling/TextFeelingProvider";
import { HealthProvider } from "../health/HealthProvider";

const textFeelingProvider = new TextFeelingProvider();
const textFeelingService = new TextFeelingService(textFeelingProvider);

const healthProvider = new HealthProvider();

export { healthProvider, textFeelingService };

// And your repositories (folder src/adapters/repositories) must have the same strategy

In this container the instances of the use cases for the specific controller are created and here the necessary dependencies for the operation of those use cases are injected, then they are exported and in the controller they are imported and used as following:

// For ExpressJs
import BaseController,{ Request, Response, NextFunction } from "../BaseController";
import { TextDto } from "../../../application/modules/feeling/dtos/TextReq.dto";
import {
  getFeelingTextUseCase,
  getHighestFeelingSentenceUseCase,
  getLowestFeelingSentenceUseCase,
} from "./container/index";

class TextFeelingController extends BaseController {
    public constructor() {
        super();
        this.InitializeRoutes();
    }
    /*...*/
    GetFeelingText = async (req: Request, res: Response, next: NextFunction): Promise<void> => {
        try {
            const textDto: TextDto = req.body;
            this.HandleResult(res, await getFeelingTextUseCase.Execute(textDto));
        } catch (error) {
            next(error);
        }
    };
    /*...*/
}

As you can see this makes it easy to manage the injection of dependencies without the need to use sophisticated libraries that add more complexity to our applications.

But if you prefer or definitely your project need a library, you can use something like awilix or inversifyJs.

Using NodeTskeleton 👾

In this template is included the example code base for KoaJs and ExpressJs, but if you have a web framework of your preference you must configure those described below according to the framework.

Using with KoaJs 🦋

The easy way is to switch to the with-koa branch in this repository, but if you want the more elaborate one follow these steps:

Delete dependencies and devDependencies for ExpressJs from package.json file.

Remove the express code from the following files:

• On file src/infrastructure/server/CoreModules.ts remove ExpressJs code and remove // for lines corresponding to KoaJs

• On file src/infrastructure/server/App.ts remove ExpressJs code and remove // for lines corresponding to KoaJs

• On file src/adapters/controllers/textFeeling/TextFeeling.controller.ts remove ExpressJs code and remove // for lines corresponding to KoaJs

• On file src/adapters/controllers/BaseController.ts remove ExpressJs code and remove // for lines corresponding to KoaJs

• On directories src/infrastructure/middleware remove ExpressJs code for each middleware and remove // for lines corresponding to KoaJs

And then, continue with the installation step described in this instructions.

Controllers

The location of the controllers must be in the adapters directory, there you can place them by responsibility in separate directories.

The controllers should be exported as default modules to make the handling of these in the index file of our application easier.

// Controller example with export default
import BaseController, { Context } from "../BaseController";
import { TextDto } from "../../../application/modules/feeling/dtos/TextReq.dto";
import {
  getFeelingTextUseCase,
  getHighestFeelingSentenceUseCase,
  getLowestFeelingSentenceUseCase,
} from "./container/index";

class TextFeelingController extends BaseController {
    public constructor() {
        super();
        this.InitializeRoutes();
    }
    /*...*/
}

const instance = new TextFeelingController();
// You can see the default export
export default instance;

Example of the handling of the controllers in the index file of our application:

/*...*/
// Region controllers
import productController from "./adapters/controllers/product/Product.controller";
import shoppingCarController from "./adapters/controllers/shoppingCart/ShoppingCar.controller";
import categoryController from "./adapters/controllers/category/CategoryController";
/*...*/
// End controllers

const controllers: BaseController[] = [
    productController,
    shoppingCarController,
    categoryController,
    /*...*/
];

const app = new App(controllers);
/*...*/

Routes

The strategy is to manage the routes within the controller, this allows us a better management of these, in addition to a greater capacity for maintenance and control according to the responsibilities of the controller.

/*...*/
private InitializeRoutes() {
    this.router.post("/v1/car", authorization(), this.Create);
    this.router.get("/v1/car/:idMask", authorization(), this.Get);
    this.router.post("/v1/car/:idMask", authorization(), this.Buy);
    this.router.post("/v1/car/:idMask/item", authorization(), this.Add);
    this.router.put("/v1/car/:idMask/item", authorization(), this.Remove);
    this.router.delete("/v1/car/:idMask", authorization(), this.Empty);
    /*...*/
}
/*...*/

Root path

If you need to manage a root path in your application then this part is configured in App, the infrastructure server module that loads the controllers as well:

/*...*/
private LoadControllers(controllers: BaseController[]) {
    controllers.forEach((controller) => {
        // This is the line and the parameter comes from `config`.
        controller.router.prefix(config.server.root);
        this.app.use(controller.router.routes());
        this.app.use(controller.router.allowedMethods());
    });
}
/*...*/

Using with ExpressJs 🐛

The easy way is to switch to the with-express branch in this repository, but if you want the more elaborate one follow these steps:

Delete dependencies and devDependencies for KoaJs from package.json file.

Delete all commented code (correspondig to KoaJs) in the files into following directories:

src/infrastructure/server/...,
src/adapters/controllers/...,
application/result/BaseController.ts,
src/infrastructure/middleware

And then, continue with the installation step described in this manual.

Controllers

The location of the controllers must be in the adapters directory, there you can place them by responsibility in separate directories.

The controllers should be exported as default modules to make the handling of these in the index file of our application easier.

// Controller example with export default
import BaseController, { Request, Response, NextFunction } from "../BaseController";
import { TextDto } from "../../../application/modules/feeling/dtos/TextReq.dto";
import {
    getFeelingTextUseCase,
    getHighestFeelingSentenceUseCase,
    getLowestFeelingSentenceUseCase,
} from "./container/index";

class TextFeelingController extends BaseController {
    public constructor() {
        super();
        this.InitializeRoutes();
    }
    /*...*/
}

const instance = new TextFeelingController();
// You can see the default export
export default instance;

Example of the handling of the controllers in the index file of our application:

/*...*/
// Region controllers
import productController from "./adapters/controllers/product/Product.controller";
import shoppingCarController from "./adapters/controllers/shoppingCart/ShoppingCar.controller";
import categoryController from "./adapters/controllers/category/CategoryController";
/*...*/
// End controllers

const controllers: BaseController[] = [
    productController,
    shoppingCarController,
    categoryController,
    /*...*/
];

const app = new App(controllers);
/*...*/

Routes

The strategy is to manage the routes within the controller, this allows us a better management of these, in addition to a greater capacity for maintenance and control according to the responsibilities of the controller.

/*...*/
private InitializeRoutes() {
    this.router.post("/v1/car", authorization(), this.Create);
    this.router.get("/v1/car/:idMask", authorization(), this.Get);
    this.router.post("/v1/car/:idMask", authorization(), this.Buy);
    this.router.post("/v1/car/:idMask/item", authorization(), this.Add);
    this.router.put("/v1/car/:idMask/item", authorization(), this.Remove);
    this.router.delete("/v1/car/:idMask", authorization(), this.Empty);
    /*...*/
}
/*...*/

Root path

If you need to manage a root path in your application then this part is configured in App, the infrastructure server module that loads the controllers as well:

/*...*/
private LoadControllers(controllers: BaseController[]): void {
    controllers.forEach((controller) => {
        // This is the line and the parameter comes from `config`.
        this.app.use(config.server.root, controller.router);
    });
}
/*...*/

Using with another web server framework 👽

You must implement the configuration made with ExpressJs or KoaJs with the framework of your choice and install all the dependencies and devDependencies for your framework, You must also modify the Server module, Middleware in infrastructure directory and the BaseController and Controllers in adapters directory.

And then, continue with the step installation.

Infrastructure 🏗️

The infrastructure includes a customizable HttpClient with its response model in src/infrastructure/httpClient/TResponse.ts for error control, and at the application level a class strategy src/application/shared/result/... is included as a standardized response model.

Installation 🔥

You must first clone the repo.

Then, we must install the dependencies, run:

npm install

Finally, we must update the dependencies, run:

npm update

Test your Clean Architecture 🥁

Something important is to know if we really did the job of building our clean architecture well, and this can be found very easily by following these steps:

1. Make sure you don't have any pending changes in your application to upload to your repository, otherwise upload them if you do.

2. Identify and remove adapters and infrastucture directories from your solution, as well as the index.ts file.

3. Execute the test command npm t or npm run test and the build command tsc or npm run build too, and everything should run smoothly, otherwise you violated the principle of dependency inversion or due to bad practice, application layers were coupled that should not be coupled.

4. Run the git checkout . command to get everything back to normal.

5. Most importantly, no domain entity can make use of an application service and less of a provider service (repository or provider), the application services use the entities, the flow goes from the most external part of the application to the most internal part of it.

Coupling 🧲

For the purpose of giving clarity to the following statement we will define coupling as the action of dependence, that is to say that X depends on Y to function.

Coupling is not bad if it is well managed, but in a software solution there should not be coupling of the domain and application layers with any other, but there can be coupling of the infrastructure layer or the adapters layer with the application and/or domain layer, or coupling of the infrastructure layer with the adapters layer and vice versa.

Conclusions (Personal) 💩

• The clean architecture allows us to develop the use cases and the domain (business logic) of an application without worrying about the type of database, web server framework, protocols, services, providers, among other things that can be trivial and that the same application during the development will tell us what could be the best choice for the infrastructure and adapters of our application.

• The clean architecture, the hexagonal architecture, the onion architecture and the ports and adapters architecture in the background can be the same, the final purpose is to decouple the business layer of our application from the outside world, basically it leads us to think about designing our solutions from the inside to outside and not from the outside to inside.

• When we develop with clean architecture we can more easily change any "external dependency" of our application without major concerns, obviously there are some that will require more effort than others, for example migrating from a NoSql schema to a SQL schema where probably the queries will be affected, however our business logic can remain intact and work for both models.

• The advantages that clean architecture offers us are very significant; it is one of the best practices for making scalable software that works for your business and not for your preferred framework.

• Clean architecture is basically based on the famous and well-known five SOLID principles that we had not mentioned until this moment and that we very little internalized.

And then, Visit the project.