typeorm-express-rest-scaffold

Created Thursday 07 May 2020

What is this

typeorm-express-rest-scaffold is a library to quickly build a REST service from your TypeORM model by generating a handler function that can do find or create on a model.

For example to GET a user, instead of writing an express handler and writing code to find a user and handle errors you would call ServiceBuilder, pass it your model name and let it know what parameters to expect:

  app.get('/:id', ServiceBuilder.findOne(User, ["id"]) ) // Route to find one user, accepting id as a parameter

The service builder returns a function that finds a matching user and returns it, or fails with a 404 and it can be registered using app.get.

How to use

The first thing to do is setup a TypeORM project. Assuming you already have TypeORM instaleed, you will want to create a directory for the project and then run "typeorm init":

$ mkdir typeormtest
$ typeorm init

Next install express

$ npm install --save express

Pull in typeorm-express-rest-scaffold as well:

$ npm install --save https://github.com/alterlife/typeorm-express-rest-scaffold.git

Finally update the index.ts file to initialize your express application and add routes to find users.

import "reflect-metadata";
import {createConnection} from "typeorm";
import {User} from "./entity/User";
import { ServiceBuilder } from 'typeorm-express-rest-scaffold'

createConnection().then(async connection => {

  
  const express = require('express')
  const app = express()
  const port = 3000

  app.get('/:id', ServiceBuilder.findOne(User, ["id"]) ) // Route to find one user, accepting id as a parameter
  app.get('/:firstname', ServiceBuilder.findAll(User, ["firstName"]) ) // Route to all users given a first name.

  app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))

}).catch(error => console.log(error));

And now you have a REST service that can find Users.

How does it work

Each of the functions under ServiceBuilder is a function that returns a handler function that can be registered with app.get in Express. For example:

    static findOne(Model: typeof BaseEntity, params:string[]=["id"]) // findone accepts the model and a list of parameters that the route handler can take. 
                : (request:Request, response:Response) => Promise<void> {

        return async (request:Request, response:Response) => { // We extract the parameters that we are interested in
            const searchParams = {
                ... filterKeys(request.params, params),
                ... filterKeys(request.query, params)
            }

            try { // Try to find a matching row
                response.send(await Model.findOneOrFail(searchParams)) // and return it if a match exists.
            } catch(e) {
                response.send(404) // or return a 404 if one does not.
            }
            response.end()
        }
    }

It's a quick way to get a rest endpoint that directly matches a model without writing much code.