Part-DB.Part-DB-server/docs/api/intro.md

---
title: Introduction
layout: default
parent: API
nav_order: 1
---

# Introduction

Part-DB provides a [REST API](https://en.wikipedia.org/wiki/REST) to programmatically access the data stored in the database.
This allows external applications to interact with Part-DB, extend it or integrate it into other applications.

{: .warning }
> This feature is currently in beta. Please report any bugs you find.
> The API should not be considered stable yet and could change in future versions, without prior notice.
> Some features might be missing or not working yet.
> Also be aware, that there might be security issues in the API, which could allow attackers to access or edit data via the API, which
> they normally should be able to access. So currently you should only use the API with trusted users and trusted applications.

Part-DB uses [API Platform](https://api-platform.com/) to provide the API, which allows for easy creation of REST APIs with Symfony and gives you a lot of features out of the box.
See the [API Platform documentation](https://api-platform.com/docs/core/) for more details about the API Platform features and how to use them.

## Enable the API

The API is available under the `/api` path, but not reachable without proper permissions.
You have to give the users, which should be able to access the API the proper permissions (Misceallaneous -> API).
Please note that there are two relevant permissions, the first one allows users to access the `/api/` path at all and showing the documentation,
and the second one allows them to create API tokens which is needed for authentication of external applications.
 
## Authentication

To use API endpoints, the external application has to authenticate itself, so that Part-DB knows which user is accessing the data and
which permisions the application should have. Basically this is done by creating a API token for a user and then passing it on every request 
with the `Authorization` header as bearer token, so you add a header `Authorization: Bearer <your token>`.

See [Authentication chapter]({% link api/authentication.md %}) for more details.

## API endpoints

The API is split into different endpoints, which are reachable under the `/api/` path of your Part-DB instance (so `https://your-part-db.local/api/`).
There are various endpoints for each entity type (like `part`, `manufacturer`, etc.), which allow you to read and write data and some special endpoints like `search` or `statistics`.

For example all API endpoints for managing categories are available under `/api/categories/`. Depending on the exact path and the HTTP method used, you can read, create, update or delete categories.
For most entities, there are endpoints like this:
* **GET**: `/api/categories/` - List all categories in the database (with pagination of the results)
* **POST**: `/api/categories/` - Create a new category
* **GET**: `/api/categories/{id}` - Get a specific category by its ID
* **DELETE**: `/api/categories/{id}` - Delete a specific category by its ID
* **UPDATE**: `/api/categories/{id}` - Update a specific category by its ID. Only the fields which are sent in the request are updated, all other fields are left unchanged. Be aware that you have to set the [JSON Patch](https://en.wikipedia.org/wiki/JSON_Patch) content type header (`Content-Type: application/merge-patch+json`) for this to work.

A full (interactive) list of endpoints can be displayed when visiting the `/api/` path in your browser, when you are logged in with a user, which is allowed to access the API.
There is also a link to this page, on the user settings page in the API token section.
This documentation also list all available fields for each entity type and the allowed operations.

## Formats

The API supports different formats for the request and response data, which you can control via the `Accept` and `Content-Type` headers.
You should use [JSON-LD](https://json-ld.org/) as format, which is basically JSON with some additional metadata, which allows 
to describe the data in a more structured way and also allows to link between different entities. You can achieve this by setting `Accept: application/ld+json` header to the API requests.

To get plain JSON without any metadata or links, use the `Accept: application/json` header.

Without an `Accept` header (e.g. when you call the endpoint in a browser), the API will return a HTML page with the documentation, so be sure to include the desired `Accept` header in your API requests.
If you can not control the `Accept` header, you can add an `.json` or `.jsonld` suffix to the URL to enforce a JSON or JSON-LD response (e.g. `/api/parts.jsonld`).

## OpenAPI schema

Part-DB provides a [OpenAPI](https://swagger.io/specification/) (formally Swagger) schema for the API under `/api/docs.json` (so `https://your-part-db.local/api/docs.json`).
This schema is a machine readable description of the API, which can be imported in software to test the API or even automatically generate client libraries for the API.

API generators which can generate a client library for the API from the schema are available for many programming languages, like [OpenAPI Generator](https://openapi-generator.tech/). 

An JSONLD/Hydra version of the schema is also available under `/api/docs.jsonld` (so `https://your-part-db.local/api/docs.jsonld`).

## Interactive documentation

Part-DB provides an interactive documentation for the API, which is available under `/api/docs` (so `https://your-part-db.local/api/docs`).
You can pass your API token in the form on the top of the page, to authenticate yourself and then you can try out the API directly in the browser.
This is a great way to test the API and see how it works, without having to write any code.

## Pagination

By default all list endpoints are paginated, which means only a certain number of results is returned per request.
To get another page of the results, you have to use the `page` query parameter, which contains the page number you want to get (e.g. `/api/categoues/?page=2`).
When using JSONLD, the links to the next page are also included in the `hydra:view` property of the response.

To change the size of the pages (the number of items in a single page) use the `itemsPerPage` query parameter (e.g. `/api/categoues/?itemsPerPage=50`).

See [API Platform docs](https://api-platform.com/docs/core/pagination) for more infos.

## Filtering results / Searching

When retrieving a list of entities, you can restrict the results by various filters. Almost all entities have a search filter,
which allows you to only include entities, which (text) fields match the given search term: For example if you only want to
get parts, with the Name "BC547", you can use `/api/parts.jsonld?name=BC547`. You can use `%` as wildcard for multiple characters
in the search term (Be sure to properly encode the search term, if you use special characters). For example if you want to get all parts,
whose name starts with "BC", you can use `/api/parts.jsonld?name=BC%25` (the `%25` is the url encoded version of `%`).

There are other filters available for some entities, allowing you to search on other fields, or restricting the results
by numeric values or dates. See the endpoint documentation for the available filters.

## Filter by associated entities

To get all parts with a certain category, manufacturer, etc. you can use the `category`, `manufacturer`, etc. query parameters of the `/api/parts` endpoint.
They are so called entitiy filters and accept a comma separated list of IDs of the entities you want to filter by. 
For example if you want to get all parts with the category "Resistor" (Category ID 1) and "Capacitor" (Category ID 2), you can use `/api/parts.jsonld?category=1,2`.

Suffix an id with `+` to suffix, to include all direct children categories of the given category. Use the `++` suffix to include all children categories recursively.
To get all parts with the category "Resistor" (Category ID 1) and all children categories of "Capacitor" (Category ID 2), you can use `/api/parts.jsonld?category=1,2++`.

See the endpoint documentation for the available entity filters.

## Ordering results

When retrieving a list of entities, you can order the results by various fields using the `order` query parameter.
For example if you want to get all parts ordered by their name, you can use `/api/parts/?order[name]=asc`. You can use 
this parameter multiple times to order by multiple fields.

See the endpoint documentation for the available fields to order by.

## Property filter

Sometimes you only want to get a subset of the properties of an entity, for example when you only need the name of a part, but not all the other properties.
You can achieve this using the `properties[]` query parameter with the name of the field you want to get. You can use this parameter multiple times to get multiple fields.
For example if you only want to get the name and the description of a part, you can use `/api/parts/123?properties[]=name&properties[]=description`.
It is also possible to use this filters on list endpoints (get collection), to only get a subset of the properties of all entities in the collection.

See [API Platform docs](https://api-platform.com/docs/core/filters/#property-filter) for more infos.

## Change comment

Similar to the changes using Part-DB web interface, you can add a change comment to every change you make via the API, which will be 
visible in the log of the entity.

You can pass the text for this via the `_comment` query parameter (beware the proper encoding). For example `/api/parts/123?_comment=This%20is%20a%20change%20comment`.