Chain of Responsibility Pattern Generator

Creates Chain of Responsibility pattern infrastructure for sequential request processing.

When to Use

Component Characteristics

HandlerInterface

• Defines handle method
• Optional setNext for linking
• Returns result or delegates

AbstractHandler

• Implements chain linking
• Provides base handle logic
• Simplifies concrete handlers

Concrete Handlers

• Process specific requests
• Decide to handle or pass
• Can terminate or continue chain

Generation Process

Step 1: Generate Handler Interface

Path:

src/Domain/{BoundedContext}/Handler/

1. {Name}HandlerInterface.php

   — Handler contract with setNext and handle methods

Step 2: Generate Abstract Handler

Path:

src/Domain/{BoundedContext}/Handler/

1. Abstract{Name}Handler.php

   — Base class with chain linking logic

Step 3: Generate Concrete Handlers

Path:

src/Domain/{BoundedContext}/Handler/

1. {Specific}{Name}Handler.php

   — Specific handler implementations

Step 4: Generate Chain Builder (Optional)

Path:

src/Domain/{BoundedContext}/Handler/

1. {Name}ChainBuilder.php

   — Fluent builder for chain construction

Step 5: Generate Tests

1. {Handler}Test.php

   — Individual handler tests

2. {Name}ChainTest.php

   — Chain integration tests

File Placement

src/Domain/{BoundedContext}/Handler/

src/Domain/{BoundedContext}/Handler/

src/Domain/{BoundedContext}/Handler/

src/Domain/{BoundedContext}/Handler/

src/Application/Pipeline/

tests/Unit/Domain/{BoundedContext}/Handler/

Naming Conventions

{Name}HandlerInterface

ValidationHandlerInterface

Abstract{Name}Handler

AbstractValidationHandler

{Specific}{Name}Handler

EmailValidationHandler

{Name}ChainBuilder

ValidationChainBuilder

{ClassName}Test

EmailValidationHandlerTest

Quick Template Reference

Handler Interface

interface {Name}HandlerInterface
{
    public function setNext(self $handler): self;
    public function handle({RequestType} $request): {ResultType};
}

Abstract Handler

abstract class Abstract{Name}Handler implements {Name}HandlerInterface
{
    private ?{Name}HandlerInterface $next = null;

    public function setNext({Name}HandlerInterface $handler): {Name}HandlerInterface
    {
        $this->next = $handler;
        return $handler;
    }

    public function handle({RequestType} $request): {ResultType}
    {
        if ($this->next !== null) {
            return $this->next->handle($request);
        }
        return $this->getDefaultResult();
    }

    abstract protected function getDefaultResult(): {ResultType};
}

Concrete Handler

final class {Specific}Handler extends Abstract{Name}Handler
{
    public function handle({RequestType} $request): {ResultType}
    {
        if ($this->canHandle($request)) {
            return $this->process($request);
        }
        return parent::handle($request);
    }

    private function canHandle({RequestType} $request): bool
    {
        return {condition};
    }
}

Chain Builder

final class {Name}ChainBuilder
{
    private array $handlers = [];

    public function add({Name}HandlerInterface $handler): self
    {
        $this->handlers[] = $handler;
        return $this;
    }

    public function build(): {Name}HandlerInterface
    {
        $first = $this->handlers[0];
        $current = $first;
        for ($i = 1; $i < count($this->handlers); $i++) {
            $current = $current->setNext($this->handlers[$i]);
        }
        return $first;
    }
}

Usage Examples

Validation Chain

$chain = (new ValidationChainBuilder())
    ->add(new NotEmptyValidationHandler('email'))
    ->add(new EmailValidationHandler('email'))
    ->add(new MinLengthValidationHandler('password', 8))
    ->build();

$result = $chain->validate($request);

if ($result->hasErrors()) {
    throw new ValidationException($result->getMessage());
}

Discount Chain

$vipHandler = new VipDiscountHandler();
$promoHandler = new PromoCodeDiscountHandler($promoCodes);
$bulkHandler = new BulkDiscountHandler();

$vipHandler->setNext($promoHandler);
$promoHandler->setNext($bulkHandler);

$result = $vipHandler->apply($discountRequest);

Anti-patterns to Avoid

References

For complete PHP templates and examples, see:

• references/templates.md

  — Handler Interface, Abstract Handler, Concrete Handler, Chain Builder, Pipeline templates

• references/examples.md

  — Validation Chain, Discount Chain examples and tests