Retrieving All Books - Implementation

1 - Route Name

GET /api/v1/books

For the route version prefix, we can do the following.

File: src/server.js

const getRouter = require('./routes')
const router = getRouter()
app.use('/api/v1', router) // add the prefix '/api/v1' to all our URIs

We will then proceed to include all of the book routes.

File: src/routes/index.js

const express = require('express')
const router = express.Router()

const bookRoutes = require('./book.route') // all our book routes

function getRouter() {
  router.use('/books', bookRoutes) // we prefix it here as 'books'
  
  return router
}

module.exports = getRouter

Here, we specify and create a controller method, let's call it getAllBooks.

File: src/routes/book.route.js

const express = require('express')
const router = express.Router()

const {
  getAllBooks
} = require('../controllers/book')

router.get('/', getAllBooks)

module.exports = router

This is where we will put the service layer and the response output.

File: src/controllers/book/getAllBooks.js

const catchException = require('../utils/catchExceptions')

const getAllBooks = catchException(async (req, res, next) => {
  // our code goes here...
})

module.exports = getAllBooks

Now that all the setup is done, we can proceed with the other layers in our application.

2 - Input Request

None.

3 - Middleware

None.

4 - Validation

None.

5 - Domain

The domain layer is quite simple, we want to first create a model that satisfies all our business requirements from the user stories we have in the previous chapter. We are going to create the book model as follows.

File: src/domain/models/book.model.js

const mongoose = require('mongoose')
const Schema = mongoose.Schema

const BookSchema = new mongoose.Schema({
  userId: {
    type: Schema.Types.ObjectId,
    ref: 'user'
  },
  title: {
    type: String,
    required: true
  },
  description: {
    type: String
  },
  price: {
    type: Number,
    required: true
  },
  author: {
    type: String
  },
  datePublished: {
    type: String
  },
  createdAt: {
    type: Date,
    default: Date.now
  }
})

module.exports = mongoose.model('book', BookSchema)

Then, we will wrap it in a repository. Remember why we are using repositories, we want to be able to create an abstraction layer between the concrete implementation of the model and our service layer so that we may swap out database types any time we want. In our case, we are using MongoDB. If for some reason in the future we decide to use something like MySQL, PostgresQL, or OracleDB, it would be much easier to swap out.

File: src/domain/repositories/book.repository.js

const Model = require('../models/book.model')

// Retrieve - all
const getAll = async () => {
  return await Model.find({})
}

module.exports = {
  getAll
}

And finally, our service layer.

File src/domain/services/book.service.js

const bookRepository = require('../repositories/book.repository')
const ApiException = require('../../utils/ApiException')
const mongoose = require('mongoose')

// Retrieve - all books
const getAllBooks = async () => {
  return bookRepository.getAll()
}

module.exports = {
  getAllBooks
}

6 - Events

None.

7 - Response

Here is what we will do to our controller in order to return a list of books

File: src/controllers/book.controller.js

const globalResponseDto = require('../../responses/globalResponseDto')
const booksResponseDto = require('../../responses/booksResponseDto')
const catchException = require('../../utils/catchExceptions')
const bookService = require('../../domain/services/book.service')

/**
 * Gets all book listings from the database.
 */
const getAllBooks = catchException(async (req, res) => {
  const books = await bookService.getAllBooks()

  res.json(
    globalResponseDto({
      status: 'success',
      code: 200,
      message: `List of all books in the database.`,
      data: booksResponseDto(books),
      errors: null
    })
  )
})

module.exports = getAllBooks

File: src/responses/bookResponseDTO.js

function bookResponseDTO(book) {
  return {
    id: book['id'],
    title: book['title'],
    description: book['description'],
    price: book['price'],
    author: book['author'],
    datePublished: book['datePublished']
  }
}

module.exports = bookResponseDTO

File: src/responses/booksResponseDTO.js

const bookResponseDTO = require('./bookResponseDTO')

function booksResponseDTO(books) {
  return books.map((book) => bookResponseDTO(book))
}

module.exports = booksResponseDTO