# Features { #features }

## FastAPI features { #fastapi-features }

**FastAPI** gives you the following:

### Based on open standards { #based-on-open-standards }

* Based on Python type hints.
* Validation and documentation from these types.
* Dependency Injection system.

It doesn't use a data validation, serialization and documentation third-party library like Pydantic, it has its own. So, these data type definitions would not be reusable as easily.

  private final Object subscriber;
  private final Method subscriberMethod;

  /**
   * @param eventBus The {@link EventBus} that handled the event and the subscriber. Useful for
   *     broadcasting a new event based on the error.
   * @param event The event object that caused the subscriber to throw.
   * @param subscriber The source subscriber context.
   * @param subscriberMethod the subscribed method.
   */

     * This cache is refreshed periodically based on the lastLoadedTime.
     */
    protected volatile String[] dataStoreNames = StringUtil.EMPTY_STRINGS;

    /**
     * Timestamp of the last time data store names were loaded from plugin files.
     * Used to implement a time-based cache refresh mechanism.
     * Volatile to ensure visibility across threads.
     */

So, it was a complete additional system.

It is not very popular or used nowadays.

## OpenAPI { #openapi }

OpenAPI (previously known as Swagger) is the open specification for building APIs (now part of the Linux Foundation).

**FastAPI** is based on **OpenAPI**.

     * session's repositories, allowing for request-specific repository configuration.
     *
     * <p>The returned list should not contain duplicate repositories (based on their
     * equality) or null entries, as these will cause validation failures when the
     * request is processed.
     *
     * @return the list of remote repositories to use, or {@code null} to use session defaults

# GraphQL { #graphql }

As **FastAPI** is based on the **ASGI** standard, it's very easy to integrate any **GraphQL** library also compatible with ASGI.

You can combine normal FastAPI *path operations* with GraphQL on the same application.

/// tip

**GraphQL** solves some very specific use cases.

It has **advantages** and **disadvantages** when compared to common **web APIs**.

            // Set event type based on message type
            WitnessEventType eventType = convertMessageTypeToEventType(message.getType());
            notification.setEventType(eventType);
            notification.setTimestamp(message.getTimestamp());

            // Set resource name based on message content
            if (message.getResourceName() != null) {

    stream.defaultReadObject();
    keyTypeOrObjectUnderJ2cl = (Class<K>) requireNonNull(stream.readObject());
    /*
     * TODO: cpovirk - Pre-size the HashMap based on the number of enum values? (But *not* based on
     * the number of entries in the map, as that makes it easy for hostile inputs to trigger lots of
     * allocation—not that any program should be deserializing hostile inputs to begin with!)
     */

    /** Prefix used to identify role-based permissions */
    protected String rolePrefix = "{role}";

    /** Prefix used to identify group-based permissions */
    protected String groupPrefix = "{group}";

    /** Prefix used to identify user-based permissions */
    protected String userPrefix = "{user}";

    /** Prefix used to identify allow permissions */