Simple Command Bus

A simple command bus implementation.

Installation

Install as usual via composer.

Configuration

Register CommandHandlers

First, register an event listener in you Zend 3 Project.

Use configuration to register command handlers.

<?php
namespace Acme\Project

return [
// ...
'simple_bus' => [
        // ...
        'command_handlers' => [
            SignupUserCommand::class           => 'signup_user.command_handler',
            SendPasswordReminderCommand::class => 'send_password_reminder.command_handler',
            // ...
        ]
    ]
]

You can only register one handler per command. Make sure your handler implements a handle method that reflects the command name, e.g. a command Acme\SignUpUserCommand translates to handleSignUpUserCommand();

<?php
namespace Acme;

class SignupUserCommandHandler implements CommandHandlerInterface {
    public function handleSignUpUserCommand(SignUpUserCommand $command) {
    // ...
    }
}

Middleware

You can add all sorts of middleware to the execution stack. Notice that HandleCommandMiddleware should always be the last in the chain, because it's responsible for the actual command dispatching.

Example below shows the default configuration.

<?php

use Lucid\Cmd\Middleware\HandleCommandMiddleware;

return [
...
    'simple_bus' => [
        'middlewares' => [
            'simple_bus.middleware.handle_command'
        ]
    ]
];

Usage

The command bus exposes one method handle() which takes an instance of Lucid\Cmd\CommandInterface as its only argument.

<?php
namespace Acme\Domain\Command;

$commandBus->handle($command);

Middleware

Internally, the command bus dispatches a middleware chain everytime the handle() method is executed. Commandhandling itself is provided via a middleware that ships with this package. It must be configured to run as last in the middleware chain.

Below an example of a validating middleware:

<?php
namespace Acme\Commanding;

use Lucid\Cmd\CommandInterface;
use Lucid\Cmd\Middleware\DelegateInterface;
use Lucid\Cmd\Middleware\MiddlewareInterface;

class MyFancyMiddleware implements MiddlewareInterface {
    public function __construct(\Acme\Validator $validator) {...}

    public function __invoke(CommandInterface $command, DelegateInterface $next) {
        if (!$this->validator->validate($command)) {
            throw new \Acme\ValidationException('command invalid');
        }  
        
        $next($command);
    }
}