@alterior/core

Alterior

An Express-based Typescript MVC framework using decorators and Angular 2 dependency injection.

Getting started

Install the package:

npm install @alterior/core

Create an application class (usually in app.ts):

import 'reflect-metadata';
import { OnSanityCheck, OnInit, AppOptions } from '@alterior/core';

export class Application implements OnSanityCheck, OnInit {
    public altOnSanityCheck(): Promise<boolean> {
        // TODO: Perform "health" checks like connecting to database, etc
    	  return Promise.resolve(true);
    }
    
    public altOnInit() {
        console.log('Service is started!');
    }
}

Create a controller (let's say foo.ts):

import { Controller, Get, RouteEvent } from '@alterior/core';
import * as express from 'express';

@Controller()
export class FooController {
    @Get('/foo')
    public foo(ev : RouteEvent)
    {
        res.status(200).send("/foo works!");
    }
    
    /**
     * You can also return promises, or 
	 * request the Express request/response explicitly (note that this is 
	 * based on the parameter name, see below for more information about
	 * route method parameters.  
     */
    @Get('/bar')
    public bar(req : express.Request, res : express.Response)
    {
        return Promise.resolve({ nifty: 123 });
    }
    
    @Get('/error')
    public errorExample(req : express.Request, res : express.Response)
    {
		//  Promises can reject
        return Promise.reject(new HttpException(301, {message: "No, over there"}));
    }

    @Get('/error')
    public errorExample(req : express.Request, res : express.Response)
    {
		// Values are OK too
        return { nifty: 123};
    }
}

Import your controller at the top of app.ts. By default, all classes with the @Controller() decorator declared throughout your application will be automatically registered in your application, but you have to ensure that your class is imported for it to work. You can override this behavior by specifying autoRegisterControllers: false in your application's @AppOptions decorator. If you do so, only the controllers you specify in the controllers array of @AppOptions will be included in your application.

When using automatic discovery, the simplest way to ensure a controller gets loaded is with:

import "foo";

Finally, you must bootstrap your application. Typically this is done in a main.ts entrypoint file:

import { Application } from './app';
import { bootstrap } from '@alterior/core';

bootstrap(Application);

For the time being, it is recommended to set your Typescript to target ES5, or do a compiler pass with an ES6 transpiler before running your app in the newer Node.js versions which are otherwise capable of it. If you target ES6 you will get an error related to a class constructor being called without the new operator. This happens when Angular tries to instantiate an ES6 class. Node.js doesn't currently allow the manner of object construction Angular is using. It's a known issue, and it has to be resolved upstream, unfortunately.

You can use any build system you want, but this works well with standard tsc compilation (ie, JS alongside TS). The NPM scripts used in @alterior/core to build and test the core library could easily be used to build and test an Alterior application.

You can test your app however you want as well, but there is a smooth way to do it with supertest, mocha, and mocha-typescript from NPM. You can see this style of testing used in this repository (lib/**/*.test.ts).

Route Parameters

Alterior inspects the parameters of controller methods to determine what values to provide. Firstly, parameters of type RouteEvent will be provided with an instance of that class which contains the Express request and response objects.

@Get('/do')
doThings(ev : RouteEvent) {
	ev.response.status(404).send("Not found.");
}

Alternatively, parameters which are named request or req will also be fulfilled with the Express request. Likewise, response or res can be used to get the response object. Note that using RouteEvent is preferred and recommended since it is a type-based rule.

@Get('/do')
doThings(req : express.Request, res : express.Response) {
	res.status(404).send("Not found.");
}

Also, parameters named body will be filled with the value of request.body, which is useful since you can set the type of the parameter to whatever you need to, such as an interface describing the expected fields that clients can send. When combined with value returns, you can achieve a very natural style:

interface MyRequestType {
	action : string;
	foo? : number;
}

@Get('/do')
doThings(body : MyRequestType) {
	return {status: "success"};
}

HTTP Exceptions

The HttpException class is included to signal Alterior to send certain HTTP status codes and responses back to the client when exceptional circumstances occur.

	// Perhaps we couldn't contact a microservice needed to fulfill the request.
	throw new HttpException(502, "Service is not available");

Dependency Injection

Alterior supports dependency injection using Angular 2's dependency injector. A number of injectable services are in the box- perhaps you need access to the Express application object to do something Alterior doesn't support:

import 
@Controller()
export class FooController {
    constructor(
        private expressRef : ExpressRef
    ) {
        this.expressApp = expressRef.application;
        this.expressApp.get('/something', (req, res) => {
            res.status(200).send('/something works!');
        });
    }
    
    private expressApp : express.Application;
}

Other builtin injectables include:

• The Application class. You will be given the singleton instance of your Application class.
• ExpressRef: Provides reference to the express.Application instance as configured for your application
• Injector (from @angular/core): Provides access to the injector which resolved your class's dependencies

Applying Middleware

Alterior is based on Express (https://expressjs.com/), so naturally it supports any Express or Connect based middleware. Middleware can be used globally, it can be mounted to a specific set of URLs, or it can be declared as part of a route, just like you can with vanilla Express.

To add middleware globally you must use the @AppOptions decorator on your app class:

import * as bodyParser from 'body-parser'; // you will need to load the body-parser typings for this syntax
@AppOptions({
    middleware: [bodyParser.json()]
})
export class Application {
    // ...
}

To add "mounted" middleware:

const fileUpload = require('express-fileupload');

@AppOptions({
    middleware: [
        ['/files', fileUpload]
    ]
})
export class Application {
    // ...
}

To add route-specific middleware:

    @Get('/foo', { middleware: [bodyParser.json()] })
    public foo(req : express.Request, res : express.Response) {
        // todo
    }

MongoDB integration

As a proof-of-concept, MongoDB support is currently built into @alterior/core. Alterior is in pre-release, in the near future this functionality will be moved to a separate module. First, you must declare how you want MongoDB to connect using the @AppOptions decorator.

In your application class file (app.ts):

import { mongoProvider } from '@alterior/core';
import * as mongodb from 'mongodb';

@AppOptions({
    providers: [mongoProvider(mongodb.Db, "mongodb://localhost:27017/db")]
})
class Application {
    // ...
}

The mongoProvider() function takes a token to make available via DI (most single-connection apps should use mongodb.Db but any value or object/function reference can be used which is useful for having multiple Mongo DB connections) and it takes the URL to the mongodb server. Now you can inject mongodb.Db (or whatever token you chose) anywhere in your application:

import * as mongodb from 'mongodb';
import { Controller, Get } from '@alterior/core';
import * as express from 'express';

@Controller()
class FooController {
    constructor(
        private db : mongodb.Db
    ) {
    }
    
    @Get("/foo")
    public foo(req : express.Request, res : express.Response) {
        this.db.collection("foos").findOne({ color: blue })
            .then(item => res.status(200).send(JSON.stringify(item)))
            .catch(e => res.status(500).send("An error occurred"));
    }
}

Custom services

This is Angular 2's dependency injector, so you can define your own services just as you would in Angular. You can add providers at the bootstrap, or app-class levels.

That's great but how do you pronounce this?

Alterior is pronounced like "ulterior" but with an A. We know it's not a proper word :-)