# Extending JSON-LD AND Hydra Contexts

## JSON-LD

<p align="center" class="symfonycasts"><a href="https://symfonycasts.com/screencast/api-platform/json-ld?cid=apip"><img src="../distribution/images/symfonycasts-player.png" alt="JSON-LD screencast"><br>Watch the JSON-LD screencast</a></p>

API Platform Core provides the possibility to extend the JSON-LD context of properties. This allows you to describe JSON-LD-typed 
values, inverse properties using the `@reverse` keyword and you can even overwrite the `@id` property this way. Everything you define
within the following annotation will be passed to the context. This provides a generic way to extend the context.

```php
<?php
// api/src/Entity/Book.php

namespace App\Entity;

use ApiPlatform\Core\Annotation\ApiProperty;
use ApiPlatform\Core\Annotation\ApiResource;

/**
 * @ApiResource(iri="http://schema.org/Book")
 */
class Book
{
    // ...

    /**
     * ...
     * @ApiProperty(
     *     iri="http://schema.org/name",
     *     attributes={
     *         "jsonld_context"={
     *             "@id"="http://yourcustomid.com",
     *             "@type"="http://www.w3.org/2001/XMLSchema#string",
     *             "someProperty"={
     *                 "a"="textA",
     *                 "b"="textB"
     *             }
     *         }
     *     }
     * )
     */
    public $name;
    
    // ...
}
```

The generated context will now have your custom attributes set:

`GET /contexts/Book`

```json
{
  "@context": {
    "@vocab": "http://example.com/apidoc#",
    "hydra": "http://www.w3.org/ns/hydra/core#",
    "name": {
      "@id": "http://yourcustomid.com",
      "@type": "http://www.w3.org/2001/XMLSchema#string",
      "someProperty": {
        "a": "textA",
        "b": "textB"
      }
    }
  }
}
```

Note that you do not have to provide the `@id` attribute. If you do not provide an `@id` attribute, the value from `iri` will be used.

## Hydra

<p align="center" class="symfonycasts"><a href="https://symfonycasts.com/screencast/api-platform/hydra?cid=apip"><img src="../distribution/images/symfonycasts-player.png" alt="Hydra screencast"><br>Watch the Hydra screencast</a></p>

It's also possible to replace the Hydra context used by the documentation generator:

<code-selector>
```php
<?php
// api/src/Entity/Book.php

use ApiPlatform\Core\Annotation\ApiResource;

/**
 * ...
 * @ApiResource(itemOperations={
 *     "get"={"hydra_context"={"foo"="bar"}}
 * })
 */
class Book
{
    //...
}
```

```yaml
# api/config/api_platform/resources.yaml
App\Entity\Book:
    itemOperations:
        get:
            hydra_context: { foo: 'bar' }
```

```xml
<?xml version="1.0" encoding="UTF-8" ?>
<!-- api/config/api_platform/resources.xml -->

<resources xmlns="https://api-platform.com/schema/metadata"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="https://api-platform.com/schema/metadata
           https://api-platform.com/schema/metadata/metadata-2.0.xsd">
    <resource class="App\Entity\Book">
        <itemOperations>
            <itemOperation name="get">              
                <attribute name="hydra_context">
                    <attribute name="foo">bar</attribute>
                </attribute>
            </itemOperation>
        </itemOperations>
    </resource>
</resources>
```
</code-selector>