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Components Overview

These are the components involved in building an API Platform-based project using the principles described in this documentation.

Components Defined by Your Application​

Domain Layer​

The heart of your software. The domain layer describes the business logic and rules. It consists of entities, value objects, domain services, and other supporting classes.

In most Symfony and API Platform projects, Doctrine is used to manage the persistence of the domain layer. However, it can be anything & our API layer does not care about how the domain layer is persisted and managed.

API Resource DTOs​

These are the data transfer objects (DTOs) that are used to represent the resources in the API. In our projects, we will be using these DTOs as the ApiResource classes. Unlike most of the API Platform examples and demos you will find on the Internet, we will not be adding the ApiResource attribute to our entities.

These DTOs will usually mirror the domain entities. They usually contain a subset of the properties, but without the domain logic. And like the entities, these DTOs will usually form a rich, interconnected graph of objects.

These DTOs act as the output of the endpoints.

An entity can be mapped to one or more DTOs if we need different API representations of a specific entity. For example, we can use a specific DTO for a class of user, and a different DTO for another class or user.

Input DTOs​

The DTOs representing the input data for operations that require an input, like POST, PUT, and PATCH.

Components Defined by API Platform​

State Provider​

Used to get the output of a GET operations. Using our guidelines, you will implement a state provider for every GET operation that you define. The state provider will be responsible for fetching the entity from the domain layer, mapping it to the DTO, and returning it.

State Processor​

Modifies the state of the entity. Used by the POST, PUT, PATCH, and DELETE operations. Using our guidelines, you will implement a state processor for every operation that modifies the state of the entity.

Paginator​

A paginator is an API Platform interface used to paginate the results of a GET operations. If your endpoint is a GET operation that is supposed to return a collection of objects, you should return a paginator object instead of an array or a collection. By doing so, you will get proper paging of the results.

Components Defined By rekalogika/api-lite​

Mapper​

Maps an object to another object. The functionality is provided by rekalogika/mapper behind the scenes. It can be used to map between entities and DTOs. This mapper provides several critical features for our purposes, including handling circular references and lazy-loading target objects. Therefore, we can have interconnected DTOs and API Platform should be able to generate IRIs without causing the hydration of the entire object graph.

Paginator Applier​

A service provided by rekalogika/api-lite to automatically transform a collection of objects to a paginator. It ships with paginator appliers for Doctrine Collection, Selectable, Query, QueryBuilder, as well as Pagerfanta and Pagerfanta adapter..