example-with-express.md

Example how to create a TypeORM application with Express

• Initial setup
• Adding Express to the application
• Adding TypeORM to the application

Initial setup

Lets create a simple application called "user" which stores users in the database and allow to create, update, remove, get list of all users and a single user by id within web api.

First, create a directory called "user".

mkdir user

Then switch to directory and create a new node application:

cd user
npm init

Finish init process by filling all required applcation data.

Now we need to install and setup a TypeScript compiler. Lets install it first:

npm i typescript --save-dev

Then let's create a tsconfig.json file which contain configuration required for application to compile and run. Create it using your favorite editor and put following configuration:

{
  "compilerOptions": {
    "lib": ["es5", "es6"],
    "target": "es5",
    "module": "commonjs",
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true
  }
}

Now lets create main application endpoint - file inside src directory called app.ts:

mkdir src
cd src
touch app.ts

Let's add simple console.log inside it:

console.log("Application is up and running");

Now its time to run our application. To run it you need to compile your typescript project first:

tsc

Once you compile it you should have src/app.js file generated. You can run it:

node src/app.js

You should see "Application is up and running" message in console just right after you run the application.

You must compile your files each time you make a change, You can setup watcher or install ts-node package to avoid manual compilation each time.

Adding Express to the application

Let's add Express to our user application. First, let's install packages we need:

npm i express body-parser @types/express @types/body-parser --save

• express is express engine itself. It allows us to create a web api
• body-parser is used to setup how express would handle body sent by a client
• @types/express is used to have a type information when using express
• @types/body-parser is used to have a type information when using body parser

Let's edit src/app.ts file and add express-related logic:

import * as express from "express";
import {Request, Response} from "express";
import * as bodyParser from  "body-parser";

// create and setup express app
const app = express();
app.use(bodyParser.json());

// register routes

app.get("/users", function(req: Request, res: Response) {
    // here we will have logic to return all users
});

app.get("/users/:id", function(req: Request, res: Response) {
    // here we will have logic to return user by id
});

app.post("/users", function(req: Request, res: Response) {
    // here we will have logic to save a user
});

app.put("/users/:id", function(req: Request, res: Response) {
    // here we will have logic to update a user by a given user id
});

app.delete("/users/:id", function(req: Request, res: Response) {
    // here we will have logic to delete a user by a given user id
});

// start express server
app.listen(3000);

Now you can compile and run your project. You should have express server running now with working routes. However those routes do not return any content yet.

Adding TypeORM to the application

Finally lets add TypeORM to the application. In this example we will use mysql driver. Setup process for other drivers is similar.

Let's install required modules first:

npm i typeorm mysql reflect-metadata --save

• typeorm is typeorm package itself
• mysql is underlying database driver. If you are using other then mysql database you must install appropriate driver
• reflect-metadata is required package used to make decorators to work properly

Now let's create ormconfig.json file with database connection configuration we will use.

  {
    "type": "mysql",
    "host": "localhost",
    "port": 3306,
    "username": "test",
    "password": "test",
    "database": "test",
    "entities": ["src/entity/*.js"],
    "logging": true
  }

Configure each option as you need. For more information about connection options see here.

Let's create a User entity inside src/entity directory:

import {Entity, Column, PrimaryGeneratedColumn} from "typeorm";

@Entity()
export class User {

    @PrimaryGeneratedColumn()
    id: number;

    @Column()
    firstName: string;

    @Column()
    lastName: string;
    
}

Let's change src/app.ts file:

import * as express from "express";
import {Request, Response} from "express";
import * as bodyParser from  "body-parser";
import {createConnection} from "typeorm";
import {User} from "./User";

// create typeorm connection
createConnection().then(connection => {
    const userRepository = connection.getRepository(User);
    
    // create and setup express app
    const app = express();
    app.use(bodyParser.json());
    
    // register routes
    
    app.get("/users", async function(req: Request, res: Response) {
        return userRepository.find();
    });
    
    app.get("/users/:id", async function(req: Request, res: Response) {
        return userRepository.findOneById(req.params.id);
    });
    
    app.post("/users", async function(req: Request, res: Response) {
        const user = userRepository.create(req.body);
        return userRepository.save(user);
    });
    
    app.delete("/users/:id", async function(req: Request, res: Response) {
        return userRepository.removeById(req.params.id);
    });
    
    // start express server
    app.listen(3000);
});

If you want to extract action callbacks into separate files and you need connection instance, you can simply use getConnection method from typeorm:

import {getConnection} from "typeorm";
import {User} from "./User";

export function UsersListAction(req: Request, res: Response) {
    return getConnection().getRepository(User).find();
}

You even don't need getConnection in this example - you can directly use getRepository function:

import {getRepository} from "typeorm";
import {User} from "./User";

export function UsersListAction(req: Request, res: Response) {
    return getRepository(User).find();
}