kodcube/command-bus

Middleware Command Bus

Middleware Based Command Bus

A simple command bus that uses the middleware pattern for processing commands., _(*1)

It has been designed to leaverage Dependency Injection with Autowiring support. All of it's dependencies and be configured & overridden by a dependency injection container, _(*2)

Main Features

• All Dependancies are injected at construction
• All Dependencies are based on interfaces
• Route Commands differently based on custom middleware
• Use simple arrays for middleware configuration
• Uses Dependency Injection Container when loading middleware
• Uses Dependency Injection Container when loading handlers

Limitations

• Does not inject dependencies for methods other than __constructor
• Does not inject dependencies for setters

Requirements

• PHP 7
• Container-Interop - Dependancy Injection Container
• GunnaPHP\Invoker

Optional

• KodCube\DependencyInjection - Dependancy Injection Container
• KodCube\MessageBus - Dispatching commands to background processes

Usage

• Create Command Bus
• Dispatch Command
• Override Command Handler
• Multiple Handlers

Create Command Bus

This will create a command bus with the default handler detection, _(*3)

``` PHP $commandbus = new KodCube\CommandBus\CommandBus( new KodCube\CommandBus\MiddlewareManager( new KodCube\DependencyInjection\Container() ) );, <sub>(*4)</sub>

or using dependancy injection container

``` PHP
DI Config
[
    MiddlewareManagerInterface::class => MiddlewareManager::class,
    ContainerInterface::class => Container::class
]

$commandbus = $di->get(KodCube\CommandBus\CommandBus::class);

Dispatch Command

Assuming you have the following command and handler, <sub>(*5)</sub>

Command Class: MyCommand, <sub>(*6)</sub>

Handler Class: MyHandler, <sub>(*7)</sub>

``` PHP $command = new MyCommand();, <sub>(*8)</sub>

$response = $commandbus($command); or $response = $commandbus->handle($command);, <sub>(*9)</sub>

is the equivalant to 

``` PHP
$command = new MyCommand();
$handler = new MyHandler();

$response = $handler($command);

Override Command Handler

The default handler middleware allows you to override which handler is responsible for handling the command, <sub>(*10)</sub>

``` PHP $commandbus = new KodCube\CommandBus\CommandBus( new KodCube\CommandBus\MiddlewareManager( new KodCube\DependencyInjection\Container(), new KodCube\CommandBus\Middleware\Handler( [ MyCommand::class => MyNewHandler::class ] ) ) );, <sub>(*11)</sub>

is the equivalant to 

``` PHP
$command = new MyCommand();
$handler = new MyNewHandler();

$response = $handler($command);

or using dependancy injection container, <sub>(*12)</sub>

``` PHP DI Config [ MiddlewareManagerInterface::class => MiddlewareManager::class, ContainerInterface::class => Container::class Handler::class => [ [ MyCommand::class => MyNewHandler::class ] ] ], <sub>(*13)</sub>

$commandbus = $di->get(KodCube\CommandBus\CommandBus::class);, <sub>(*14)</sub>

### Multiple Middlerware Handlers

Using the middleware capablies we can easily add multiple command handlers, to process some commands differently from others.

In this example we add a Queueable Middleware Handler, that will look for commands that implement a *CommandQueueInterface::class*.

Theses commands will be routed to a message bus for processing on a background process, were as all other command will be handled by the final middleware handler.

``` PHP
$commandbus = new KodCube\CommandBus\CommandBus(
                new KodCube\CommandBus\MiddlewareManager(
                    [
                      KodCube\CommandBus\Middleware\Queue::class,
                      KodCube\CommandBus\Middleware\Handler::class
                    ],
                    new KodCube\DependencyInjection\Container(), 
                  )
              );

or using dependancy injection container, <sub>(*15)</sub>

``` PHP DI Config [ MiddlewareManagerInterface::class => MiddlewareManager::class, MiddlewareManager::class => [ Middleware\Queue::class, Middleware\Handler::class ], ContainerInterface::class => Container::class, Handler::class => [ [ MyCommand::class => MyNewHandler::class ] ] ], <sub>(*16)</sub>

$commandbus = $di->get(KodCube\CommandBus\CommandBus::class); ```, <sub>(*17)</sub>