# Data providers

Data providers are the core means to access external data. These are classes which use custom methods to access data.

Available data providers:

* [Http](/data/retrieving-data/http.md) - generic HTTP data provider
* [Rest](https://github.com/strata/data/blob/main/docs/retrieving-data/rest.md) - data provider for REST-based APIs
* [GraphQL](/data/retrieving-data/data-providers.md) - data provider for GraphQL APOIs

## Common methods

A `DataProvider` interface is used which defines the following common methods for data providers.

### getBaseUri

Return base URI to use for all data requests.

* Returns a string

### getUri

Return URI to use for current data request

* Parameters
  * `string|null $endpoint` Optional endpoint to append to base URI
* Returns a string

### getRequestIdentifier

Return a unique identifier safe to use for caching based on the request

* Parameters
  * `$uri` URI for request
  * `array $context` Array of contextual data (e.g. request options)
* Returns a string

### isSuppressErrors

Whether errors are suppressed

* Returns a boolean

### getDefaultDecoder

Return default decoder to decode responses.

* Returns an object of type `Strata\Data\Decode\DecoderInterface` or null if no default decoder set

### decode

Decode a response

* Parameters
  * `mixed $response` Response to decode (normally an object or array)
  * `DecoderInterface|null $decoder` Optional decoder, if not set uses getDefaultDecoder()
* Returns the decoded data (normally an array or object)

### isCacheEnabled

Is the cache enabled?

* Returns a boolean

### getCache

Return the cache

* Returns an object of type `Strata\Data\Cache\DataCache`

### addListener

Adds an event listener that listens on the specified event. See [events](/data/advanced-usage/events.md).

* Parameters
  * `string $eventName` Event name
  * `callable $listener` The listener
  * `int $priority` The higher this value, the earlier an event listener will be triggered in the chain (defaults to 0)

### addSubscriber

Adds an event subscriber. See [events](/data/advanced-usage/events.md).

* Parameters
  * `EventSubscriberInterface $subscriber` Event subscriber

### dispatchEvent

Dispatches an event to all registered listeners

* Parameters
  * `Event $event` The event to pass to the event handlers/listeners
  * `string $eventName` The name of the event to dispatch
* Returns an object of type `Symfony\Contracts\EventDispatcher\Event`


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