Object Mapper

Index

• Meta
• Introduction
• Roadmap
  • v1.1.0
• Integrations
• Setup
  • Step 1 - Installation
  • Step 2 - Initialization
• Mapping
  • Overview
  • Automatic Mapping
    • Static Path Finder
    • Static Source To Dynamic Target Path Finder
    • Dynamic Source To Static Target Path Finder
    • Custom Path Finder
  • Manual Mapping
    • Via Map Builder API
    • Via Map Definition Preloading
  • Check Point
  • Recursion

Meta

This document is a guide mainly walking you through the setup, concepts, and use cases of this solution.

API documentation is bound to code and complies to PHPDoc standards...

Secondary sections are collapsed in order to not overflow the first reading.

Introduction

Use this solution for mapping generically data from source to target object via extensible strategies and controls.

Delegate responsibility of all of your data mapping to a generic - extensible - optimized - tested mapping system.

Leverage that system to:

• Decouple your codebase from data mapping logic
• Dynamically define control flow over data being transferred from source to target
• Dynamically define target model based on source model and vice-versa
• Easily genericize - centralize - optimize - test - execute data mapping
• Design efficiently and simplify your system

This project aims to provide a standard core system to higher level systems such as:

• ORM
• Form handler
• Serializer
• Data import
• Layers data representation mapper
• ...

If you need to map from/to array data structure, simply cast it to/from object stdClass.

Roadmap

To develop this solution faster, contributions are welcome...

v1.1.0

• Implement recursion path finder feature
• Implement callable check point feature
• Implement seizing check point feature
• Improve doc

Integrations

• Symfony 4 application => opportus/object-mapper-bundle
• {{ reference_here_your_own_integration }}

Setup

Step 1 - Installation

Open a command console, enter your project directory and execute:

$ composer require opportus/object-mapper

Step 2 - Initialization

This library contains 4 services. 3 of them require a single dependency which is another lower level service among those 4:

use Opportus\ObjectMapper\Point\PointFactory;
use Opportus\ObjectMapper\Route\RouteBuilder;
use Opportus\ObjectMapper\Map\MapBuilder;
use Opportus\ObjectMapper\ObjectMapper;

$pointFactory = new PointFactory();
$routeBuilder = new RouteBuilder($pointFactory);
$mapBuilder   = new MapBuilder($routeBuilder);
$objectMapper = new ObjectMapper($mapBuilder);

In order for the object mapper to get properly initialized, each of its services must be instantiated such as above.

By design, this solution does not provide "helpers" for the instantiation of its own services which is much better handled the way you're already instantiating your own services, with a DIC system or whatever.

Mapping

Overview

In order to transfer data from a source object to a target object, the ObjectMapper iterates through each Route that it gets from a Map, assigning the value of the current route's source point to this route's target point.

Optionally, on the route, check points can be defined in order to control the value from the source point before it reaches the target point.

A route is defined by and composed of its source point, its target point, and its check points.

A source point can be either:

• A property
• A method
• Any extended type of source point

A target point can be either:

• A property
• A method parameter
• Any extended type of target point

A check point can be any implementation of CheckPointInterface.

These routes can be defined automatically via a map's PathFinderInterface strategy implementation and/or manually via:

• Map builder API
• Map definition preloading

Automatic Mapping

Remember that PathFinderInterface implementations such as those covered next in this section can get combined.

Static Path Finder

A basic example of how to automatically map User's data to UserDto and vice-versa:

class User
{
    private $username;

    public function __construct(string $username)
    {
        $this->username = $username;
    }

    public function getUsername(): string
    {
        return $this->username;
    }
}

class UserDto
{
    public $username;
}

$user    = new User('Toto');
$userDto = new UserDto();

// Map the data of the User instance to the UserDto instance
$objectMapper->map($user, $userDto);

echo $userDto->username; // Toto

// Map the data of the UserDto instance to a new User instance
$user = $objectMapper->map($userDto, User::class);

echo $user->getUsername(); // Toto

Calling the ObjectMapper::map() method passing no $map argument makes the method build then use a Map composed of the default StaticPathFinder strategy.

The default StaticPathFinder strategy determines the appropriate point of the source class to connect to each point of the target class. Doing so, it defines a route to follow by the object mapper.

For the default StaticPathFinder, a reference target point can be:

• A public property (PropertyStaticTargetPoint)
• A parameter of a public setter or constructor (MethodParameterStaticTargetPoint)

The corresponding source point can be:

• A public property having for name the same as the target point (PropertyStaticSourcePoint)
• A public getter having for name 'get'.ucfirst($targetPointName) and requiring no argument (MethodStaticSourcePoint)

Static Source To Dynamic Target Path Finder

Click for details

A basic example of how to automatically map User's data to DynamicUserDto:

class DynamicUserDto {}

$user    = new User('Toto');
$userDto = new DynamicUserDto();

// Build the map
$map = $mapBuilder
    ->addStaticSourceToDynamicTargetPathFinder()
    ->getMap();

// Map the data of the User instance to the DynamicUserDto instance
$objectMapper->map($user, $userDto, $map);

echo $userDto->username; // Toto

The default StaticSourceToDynamicTargetPathFinder strategy determines the appropriate point of the target object (dynamic point) to connect to each point of the source class (static point).

For the default StaticSourceToDynamicTargetPathFinder, a reference source point can be:

• A public property (PropertyStaticSourcePoint)
• A public getter requiring no argument (MethodStaticSourcePoint)

The corresponding target point can be:

• A statically undefined (not existing in class) property having for name the same as the property source point or lcfirst(substr($getterSourcePoint, 3)) (PropertyDynamicTargetPoint)

Dynamic Source To Static Target Path Finder

Click for details

A basic example of how to automatically map DynamicUserDto's data to User:

class DynamicUserDto {}

$userDto = new DynamicUserDto();
$userDto->username = 'Toto';

// Build the map
$map = $mapBuilder
    ->addDynamicSourceToStaticTargetPathFinder()
    ->getMap();

// Map the data of the DynamicUserDto instance to a new User instance
$user = $objectMapper->map($userDto, User::class, $map);

echo $user->getUsername(); // Toto

The default DynamicSourceToStaticTargetPathFinder strategy determines the appropriate point of the source object (dynamic point) to connect to each point of the target class (static point).

For the default StaticSourceToDynamicTargetPathFinder, a reference target point can be:

• A public property (PropertyStaticTargetPoint)
• A parameter of a public setter or constructor (MethodParameterStaticTargetPoint)

The corresponding source point can be:

• A statically undefined (not existing in class) but dynamically defined (existing in object) property having for name the same as the target point (PropertyDynamicSourcePoint)

Custom Path Finder

The default path finders presented above implement each a specific mapping logic. In order for those to generically map differently typed objects, they have to follow a certain convention de facto established by these path finders. You can map generically differently typed objects only accordingly to the path finders the map is composed of.

If the default path finders do not suit your needs, you still can genericize and encapsulate your domain's mapping logic as subtype(s) of PathFinderInterface. Doing so effectively, you leverage Object Mapper to decouple these objects from your mapping logic... Indeed, when the mapped objects change, the mapping doesn't.

For best example of how to implement PathFinderInterface, refer to the default StaticPathFinder, StaticSourceToDynamicTargetPathFinder, and DynamicSourceToStaticTargetPathFinder implementations.

Example

class MyPathFinder implements PathFinderInterface
{
    private $routeBuilder;

    // ...

    public function getRoutes(SourceInterface $source, TargetInterface $target): RouteCollection
    {
        $source->getClassReflection();
        $target->getClassReflection();
        
        $routes = [];

        /**
         * Custom mapping algorithm based on source/target relection and
         * possibly their data...
         * 
         * Use route builder to build routes...
         */

        return new RouteCollection($routes);
    }
}

// Pass to the map builder pathfinders you want it to compose the map of
$map = $mapBuilder
    ->addStaticPathFinder()
    ->addPathFinder(new MyPathFinder($routeBuilder))
    ->getMap();

// Use the map
$user = $objectMapper->map($userDto, User::class, $map);

Manual Mapping

If in your context, such as walked through in the previous "automatic mapping" section, a mapping strategy is impossible, you can manually map the source to the target.

There are multiple ways to define manually the mapping such as introduced in the 2 next sub-sections:

• Via map builder API
• Via map definition preloading

Via Map Builder API

Click for details

The MapBuilder is an immutable service which implement a fluent interface.

A basic example of how to manually map User's data to ContributorDto and vice-versa with the MapBuilder:

class User
{
    private $username;

    public function __construct(string $username)
    {
        $this->username = $username;
    }

    public function getUsername(): string
    {
        return $this->username;
    }
}

class ContributorDto
{
    public $name;
}

$user = new User('Toto');
$contributorDto = new ContributorDto();

// Define the route manually
$map = $mapBuilder
    ->getRouteBuilder()
        ->setStaticSourcePoint('User::getUsername()')
        ->setStaticTargetPoint('ContributorDto::$name')
        ->addRouteToMapBuilder()
        ->getMapBuilder()
    ->getMap();

// Map the data of the User instance to the ContributorDto instance
$objectMapper->map($user, $contributorDto, $map);

echo $contributorDto->name; // Toto

// Define the route manually
$map = $mapBuilder
    ->getRouteBuilder()
        ->setStaticSourcePoint('ContributorDto::$name')
        ->setStaticTargetPoint('User::__construct()::$username')
        ->addRouteToMapBuilder()
        ->getMapBuilder()
    ->getMap();

// Map the data of the ContributorDto instance to a new User instance
$user = $objectMapper->map($contributorDto, User::class, $map);

echo $user->getUsername(); // 'Toto'

Via Map Definition Preloading

Click for details

Via the map builder API presented above, we define the map (adding to it routes) on the go. There is another way to define the map, preloading its definition.

While this library is designed with map definition preloading in mind, it does not provide a way to effectively preload a map definition which could be:

• Any type of file, commonly used for configuration (XML, YAML, JSON, etc...), defining statically a map to build at runtime
• Any type of annotation in source and target classes, defining statically a map to build at runtime
• Any type of PHP routine, defining dynamically a map to build at runtime
• ...

A map being not much more than a collection of routes, you can statically define it for example by defining its routes FQN this way:

map:
  - source1::$property=>target1::$property
  - source1::$property=>target2::$property
  - source2::$property=>target2::$property

Then at runtime, in order to create routes to compose a map of, you can:

• Parse your map configuration files, extract from them route definitions
• Parse your source and target annotations, extract from them route definitions
• Implement any sort of map generator logic outputing route definitions

Then, based on their definitions, build these routes with the initial instance of the MapBuilder which will keep and inject them into its built maps which in turn might return these routes to the object mapper depending on the source and target being mapped.

Because an object mapper has a wide range of different use case contexts, this solution is designed as a minimalist, flexible, and extensible core in order to get integrated, adapted, and extended seamlessly into any of these contexts. Therefore, this solution delegates map definition preloading to the integrating higher level system which can make use contextually of its own DIC, configuration, and cache systems required for achieving map definition preloading.

opportus/object-mapper-bundle is one system integrating this library (into Symfony 4 application context). You can refer to it for concrete examples of how to implement map definition preloading.

Check Point

A check point, added to a route, allows you to control/transform the value from the source point before it reaches the target point.

You can add multiple check points to a route. In this case, these check points form a chain. The first check point controls the original value from the source point and returns the value (transformed or not) to the object mapper. Then, the object mapper passes the value to the next check point and so on... Until the last check point returns the final value to be assigned to the target point by the object mapper.

So it is important to keep in mind that each check point has a unique position (priority) on a route. The routed value goes through each of the check points from the lowest to the highest positioned ones such as represented below:

SourcePoint --> $value' --> CheckPoint1 --> $value'' --> CheckPoint2 --> $value''' --> TargetPoint

A simple example implementing CheckPointInterface, and PathFinderInterface, to form what we could call a presentation layer:

class Contributor
{
    private $bio;

    public function __construct(string $bio)
    {
        $this->bio = $bio;
    }

    public function getBio(): string
    {
        return $this->bio;
    }
}

class ContributorView
{
    public $bio;
}

class GenericViewHtmlTagStripper implements CheckPointInterface
{
    public function control($value, RouteInterface $route, MapInterface $map, SourceInterface $source, TargetInterface $target)
    {
        return \strip_tags($value);
    }
}

class GenericViewMarkdownTransformer implements CheckPointInterface
{
    // ...
    public function control($value, RouteInterface $route, MapInterface $map, SourceInterface $source, TargetInterface $target)
    {
        return $this->markdownParser->transform($value);
    }
}

class GenericPresentation extends StaticPathFinder
{
    // ...
    public function getRoutes(Source $source, Target $target): RouteCollection
    {
        $routes = parent::getRoutes($source, $target);

        $controlledRoutes = [];

        foreach ($routes as $route) {
            $controlledRoutes[] = $this->routeBuilder
                ->setSourcePoint($route->getSourcePoint()->getFqn())
                ->setTargetPoint($route->getTargetPoint()->getFqn())
                ->addCheckPoint(new GenericViewHtmlTagStripper(), 10)
                ->addCheckPoint(new GenericViewMarkdownTransformer($this->markdownParser), 20)
                ->getRoute();
        }

        return new RouteCollection($controlledRoutes);
    }
}

$contributor = new Contributor('<script>**Hello World!**</script>');

$map = $mapBuilder
    ->addPathFinder(new GenericPresentation($markdownTransformer))
    ->getMap();

$contributorView = $objectMapper->map($contributor, ContributorView::class, $map);

echo $contributorView->bio; // <b>Hello World!</b>

In this example, based on the Object Mapper's abilities, we code a whole application generic layer with no effort...

But what is a layer? Accordingly to Wikipedia:

An abstraction layer is a way of hiding the working details of a subsystem, allowing the separation of concerns to facilitate interoperability and platform independence.

The more the root system (say an application) has independent layers, the more it has data representations, the more it has to map data from one representation to another.

Think for example of the Clean Architecture:

• Controller maps its (POST) request representation to its corresponding interactor/usecase request representation
• Interactor maps its usecase request representation to its corresponding domain entity representation
• Entity gateway maps its domain entity representation to its corresponding persistence representation, and vice-versa
• Presenter maps its domain entity representation to its corresponding view representation

Each of these layers' essence is to map data based on the logic they are composed of. This logic is what we can calle the flow of control over data.

Referring to our example... This flow of control is defined by the path finder. These controls are our check points. The ObjectMapper service is nothing but that concrete layered system. Such layered OOP system is an object mapper.

Recursion

A recursion implements CheckPointInterface. It is used to recursively map a source point to a target point.

This means:

• During mapping an instance of A (that has C) to B (that has D), mapping in same time C to D, AKA simple recursion.
• During mapping an instance of A (that has many C) to B (that has many D), mapping in same time many C to many D, AKA in-width recursion or iterable recursion.
• During mapping an instance of A (that has C which has E) to B (that has D which has F), mapping in same time C and E to D and F, AKA in-depth recursion.

An example of how to manually map a Post and its composite objects to its PostDto and its composite DTO objects:

class Post
{
    public Author $author;
    public Comment[] $comments;
}

class Author
{
    public string $name;
}

class Comment
{
    public Author $author;
}

class PostDto {}
class AuthorDto {}
class CommentDto {}

$comment1 = new Comment();
$comment1->author = new Author();
$comment1->author->name = 'clem';

$comment2 = new Comment();
$comment2->author = new Author();
$comment2->author->name = 'bob';

$post = new Post();
$post->author = new Author();
$post->author->name = 'Martin Fowler';
$post->comments = [$comment1, $comment2];

// Let's map the Post instance above and its composites to a new PostDto instance and DTO composites...
$mapBuilder
    ->getRouteBuilder
        ->setStaticSourcePoint('Post::$author')
        ->setDynamicTargetPoint('PostDto::$author')
        ->addRecursionCheckPoint('Author', 'AuthorDto', 'PostDto::$author') // Mapping also Post's Author to PostDto's AuthorDto
        ->addRouteToMapBuilder()

        ->setStaticSourcePoint('Comment::$author')
        ->setDynamicTargetPoint('CommentDto::$author')
        ->addRecursionCheckPoint('Author', 'AuthorDto', 'CommentDto::$author') // Mapping also Comment's Author to CommentDto's AuthorDto
        ->addRouteToMapBuilder()

        ->setStaticSourcePoint('Post::$comments')
        ->setDynamicTargetPoint('PostDto::$comments')
        ->addIterableRecursionCheckPoint('Comment', 'CommentDto', 'PostDto::$comments') // Mapping also Post's Comment's to PostDto's CommentDto's
        ->addRouteToMapBuilder()
    ->getMapBuilder()
    ->addStaticSourceToDynamicTargetPathFinder()
    ->getMap();

$postDto = $objectMapper->($post, PostDto::class, $map)

get_class($postDto); // PostDto

get_class($postDto->author); // AuthorDto
echo $postDto->author->name; // Matin Fowler

get_class($postDto->comments[0]); // CommentDto
get_class($postDto->comments[0]->author); // AuthorDto
echo $postDto->comments[0]->author->name; // clem

get_class($postDto->comments[1]); // CommentDto
get_class($postDto->comments[1]->author); // AuthorDto
echo $postDto->comments[1]->author->name; // bob

Naturally, all that can get simplified with a higher level PathFinderInterface implementation defining these recursions automatically based on source and target point types. These types being hinted in source and target classes either with PHP or PHPDoc.

This library may feature such PathFinder in near future. Meanwhile, you still can implement yours, and maybe submit it to pull request... :)