Curli-Bus

Simple Command/Query/Event Bus Implementation to use with CQRS or DDD for NodeJS/Typescript.

Motivation

There are a lot of bus CQRS libraries for JavaScript/Typescript out there, this is not new. The one thing we're trying to achieve here is the ability to take advantage of such a library but without coupling it into the application's domain. The main goal here is to create a library that you can use without using third part code into your domains.

Installation

Install by npm

npm install --save curli-bus

Basic Usage

Command Bus:

import {CommandBusSync, CommandInstanceType} from "curli-bus";

class CommandTest {
    public constructor (private name: string){
    }
}

const commandBus = new CommandBusSync();

bus.registerHandler(CommandTest, function (command: CommandInstanceType): any {
    container.get('useCase').execute(command);
});

const commandTest = new CommandTest('test');
bus.dispatch(commandTest);

Registering command using string name

bus.registerHandler('CommandTest', function (command: CommandInstanceType): any {
    container.get('useCase').execute(command);
});

const commandTest = new CommandTest('test');
bus.dispatch(commandTest);

Using options

We can send options to the handler through all the middleware.

bus.registerHandler('CommandTest', function (command: CommandInstanceType, options?: any): any {
    container.get('useCase').execute(command, options);
});

bus.dispatch(commandTest, {"dev": true});

Using middleware

import {BusSync, CommandInstanceType, Middleware} from "curli-bus";

class CommandTest {
    public constructor (private name: string){
    }
    
    public addToName (toAdd: string) {
        this.name = this.name + ' - ' + toAdd + ' -';
    }
}

class MiddlewareTest extends Middleware {
    execute (command: CommandInstanceType, next: (a: any) => any): any {
        command.addToName('preHandler');
        command = next(command);
        command.addToName('postHandler');
        return command;
    }
}

const bus = new BusSync();
const commandTest = new CommandTest('test');

bus.addMiddleware(new MiddlewareTest());

bus.registerHandler(CommandTest, function (command: CommandInstanceType): any {
    command.addToName('hendler');
    container.get('useCase').execute(command);
});

commandTest = bus.dispatch(commandTest);

console.log(commandTest.name);
//test - preHandler - hendler - postHandler -

Query Bus:

import {QueryBusSync, QueryInstanceType} from "curli-bus";

class QueryTest {
    public constructor (private query: object){
    }
}

const queryBus = new QueryBusSync();

bus.registerHandler(QueryTest, function (query: QueryInstanceType): any {
    container.get('useCase').execute(query);
});

const queryTest = new QueryTest({'name': 'test'});
const result = bus.ask(queryTest);

Registering query using string name

bus.registerHandler('QueryTest', function (query: QueryInstanceType): any {
    container.get('useCase').execute(query);
});

const queryTest = new QueryTest({'name': 'test'});
const result = bus.ask(queryTest);

Using options

We can send options to the handler through all the middleware.

bus.registerHandler('QueryTest', function (query: QueryInstanceType, options?: any): any {
    container.get('useCase').execute(query, options);
});

const result = bus.ask(queryTest, {"dev": true});

Using middleware

import {BusSync, QueryInstanceType, Middleware} from "curli-bus";

class QueryTest {
    public constructor (private name: string){
    }
    
    public addToName (toAdd: string) {
        this.name = this.name + ' - ' + toAdd + ' -';
    }
}

class MiddlewareTest extends Middleware {
    execute (query: QueryInstanceType, next: (a: any) => any): any {
        query.addToName('preHandler');
        query = next(query);
        query.addToName('postHandler');
        return query;
    }
}

const bus = new BusSync();
const queryTest = new QueryTest('test');

bus.addMiddleware(new MiddlewareTest());

bus.registerHandler(QueryTest, function (query: QueryInstanceType): any {
    query.addToName('hendler');
    container.get('useCase').execute(query);
});

const result = bus.ask(queryTest);

console.log(result.name);
//test - preHandler - hendler - postHandler -

Event Bus

We can create an event bus and send events throw it.

import {EventBus} from "curli-bus";

class UserCreatedEvent {
    public eventName = 'user_created';
    public dateTimeOccurred?: Date;
    public constructor(public data: {[key:string]: any}) {
    }
}

class OnUserCreatedEventSubscriber {
    public getEventName(): string {
    	return 'user_created';
    }
    public handle (event: Event): any{
       //... Do stuff with the event
    }
}

const eventBus = new EventBus();

eventBus.register(new OnUserCreatedEventSubscriber());

const event = new UserCreatedEvent(
    {userName: 'Josh', email:'[email protected]'}
);
eventBus.publish(event);

Commands

• npm run build: Build the project (Bus).
• npm run build:clean: Delete first the dist folder and build it.
• npm run clean: Delete the dist folder.
• npm run test: Execute the tests.
• npm run test:coverage: Execute the tests and calculate the coverage.
• npm run lint: Check the code using the rules in .eslintre.js
• npm run lint:fix: Check the code and try to fix it.

Contributing

When submitting your pull-request try to follow those guides:

• https://egghead.io/courses/how-to-contribute-to-an-open-source-project-on-github

• https://medium.com/@vadimdemedes/making-your-first-contribution-de6576ddb190

Changelog

All notable changes to this project will be documented in this section.

0.2.1

Changed

• Expose Event interface and EventSubscriber type

0.2.0

Added

• Support publish multiple events (array) in event bus.

0.1.0

Added

• Event bus support

0.0.2

Added

• QueryBusSync support

Changed

• BusSync interface will be CommandBusSync

0.0.1

Added

• CommandBusSync support

License

MIT