@dvsa/cvs-microservice-common v1.4.3

cvs-microservice-common

Common code used by the various serverless microservices within the Commercial Vehicle Services (CVS) system, published as a GitHub package.

Pre-requisites

• Node.js (Please see .nvmrc for specific version)
• npm (If using n or nvm, this will be automatically managed)
• Security
  • Git secrets
  • ScanRepo
    • Unzip repo-security-scanner_<version>_Darwin_<architercture>.tar.gz and rename the executable inside the folder to scanrepo - Add executable to path (using echo $PATH to find your path)

Getting started

Run the following command after cloning the project

1. npm install (or npm i)

The code that will be published lives inside the ./src directory.

If wishing to add new top level directories to the output, then they must be included in the files array inside package.json as well as included in the clean:temp command.

Publishing

In order to see the output of what will be published, run the following command:

npm publish --dry-run

There are two ways in which this package can/should be published:

Requires manual version bump via the PR

• Upon merge into main branch, the package will be published via a GHA workflow.

Contents

EnvironmentVariables

Overview

EnvironmentVariables is a utility class for managing environment variables in a structured way. It ensures that required environment variables are present and provides default values when necessary.

Usage

Importing the EnvironmentVariables Class

import { EnvironmentVariables } from '@dvsa/cvs-microservice-common';

Retrieving a Required Environment Variable

Use the get method to retrieve an environment variable. If the variable is missing, an error is thrown.

const apiKey = EnvironmentVariables.get("API_KEY");
console.log("API Key:", apiKey);

Example with Missing Variable

If API_KEY is not set in the environment, the following error will be thrown:

Error: Configuration item API_KEY was not provided with a value

Using a Default Value When a Variable is Absent

If an environment variable may be missing, you can use defaultIfNotPresent to provide a fallback value.

const logLevel = EnvironmentVariables.defaultIfNotPresent(process.env.LOG_LEVEL, "info");
console.log("Log Level:", logLevel);

Ensuring an Environment Variable is Set Before Proceeding

Use throwIfNotPresent when checking a variable's existence but wanting an explicit error if it's missing.

const dbHost = EnvironmentVariables.throwIfNotPresent(process.env.DB_HOST, "DB_HOST");
console.log("Database Host:", dbHost);

Error Handling

• If get or throwIfNotPresent is used on an unset variable, an error is thrown.
• defaultIfNotPresent prevents errors by returning a default value when the variable is missing.

Example .env File

API_KEY=my-secret-api-key
DB_HOST=database.example.com
LOG_LEVEL=debug

Custom Routing Decorators

Overview

This module provides custom decorators (GET, POST, and PUT) for routing-controllers, allowing API routes to be automatically prefixed with a branch name when the BRANCH environment variable is set.

Installation

Ensure you have routing-controllers installed in your project:

npm install routing-controllers

Usage

Importing the Custom Route Decorators

import { GET, POST, PUT } from '@dvsa/cvs-microservice-common/api/routing-decorators';

Defining API Endpoints with Branch-Aware Routing

These decorators extend routing-controllers' @Get, @Post, and @Put decorators by applying both the original route and a prefixed route (if BRANCH is set).

import { JsonController } from "routing-controllers";
import { GET, POST, PUT } from "@dvsa/cvs-microservice-common/api/routing-decorators";

@JsonController("/users")
export class UserController {
  @GET("/")
  getUsers() {
    return { message: "List of users" };
  }

  @POST("/")
  createUser() {
    return { message: "User created" };
  }

  @PUT("/:id")
  updateUser() {
    return { message: "User updated" };
  }
}

Effect of BRANCH Environment Variable

If BRANCH=feature-x, the above routes will be accessible at:

• GET /users/ → List users
• GET /feature-x/users/ → List users (branch-prefixed)
• POST /users/ → Create a user
• POST /feature-x/users/ → Create a user (branch-prefixed)
• PUT /users/:id → Update a user
• PUT /feature-x/users/:id → Update a user (branch-prefixed)

Setting the BRANCH Environment Variable

To enable branch-prefixed routes, set the BRANCH environment variable:

export BRANCH=feature-x

Benefits

• Supports Feature Branching: Easily test feature-specific API versions.
• Automatic Routing Prefixing: No need to manually adjust routes for different environments.
• Seamless Integration: Works with routing-controllers decorators.

HttpStatus

Overview

HttpStatus is an enumeration representing common HTTP status codes. It provides a readable and maintainable way to reference standard HTTP response codes in your application.

Usage

Importing the HttpStatus Enum

import { HttpStatus } from '@domain/enums/HttpStatus.enum';

Using HTTP Status Codes in API Responses

The HttpStatus enum can be used to improve readability and maintainability in HTTP responses.

Example Usage in an Express API

import express from "express";
import { HttpStatus } from "@domain/enums/HttpStatus.enum";

const app = express();

app.get("/status", (req, res) => {
  res.status(HttpStatus.OK).json({ message: "Success" });
});

app.use((req, res) => {
  res.status(HttpStatus.NOT_FOUND).json({ error: "Not Found" });
});

app.listen(3000, () => console.log("Server running on port 3000"));

Common Status Codes

Benefits of Using HttpStatus

• Improved Readability: Instead of using magic numbers, named constants make code clearer.
• Better Maintainability: Centralized status codes make updates easier.
• Reduced Errors: Avoid mistyping HTTP status codes.