# Einstellungen und Umgebungsvariablen

In vielen Fällen benötigt Ihre Anwendung möglicherweise einige externe Einstellungen oder Konfigurationen, zum Beispiel geheime Schlüssel, Datenbank-Anmeldeinformationen, Anmeldeinformationen für E-Mail-Dienste, usw.

Die meisten dieser Einstellungen sind variabel (können sich ändern), wie z. B. Datenbank-URLs. Und vieles könnten schützenswerte, geheime Daten sein.

# OpenAPI erweitern

In einigen Fällen müssen Sie möglicherweise das generierte OpenAPI-Schema ändern.

In diesem Abschnitt erfahren Sie, wie.

## Der normale Vorgang

Der normale (Standard-)Prozess ist wie folgt.

Eine `FastAPI`-Anwendung (-Instanz) verfügt über eine `.openapi()`-Methode, von der erwartet wird, dass sie das OpenAPI-Schema zurückgibt.

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps

The process normally is that **you define** in your code what is the message that you will send, the **body of the request**.

	b.r++
	b.lastByte = int(c)
	return c, nil
}

// UnreadByte unreads the last byte. Only the most recently read byte can be unread.
//
// UnreadByte returns an error if the most recent method called on the
// [Reader] was not a read operation. Notably, [Reader.Peek], [Reader.Discard], and [Reader.WriteTo] are not
// considered read operations.
func (b *Reader) UnreadByte() error {

  fun statementStartsAndStops() {
    val called = AtomicBoolean()
    val statement =
      server.apply(
        object : Statement() {
          override fun evaluate() {
            called.set(true)
            server.url("/").toUrl().openConnection().connect()
          }
        },
        Description.EMPTY,
      )
    statement.evaluate()
    assertThat(called.get()).isTrue()
    try {

/// note | "Technical Details"

Data from forms is normally encoded using the "media type" `application/x-www-form-urlencoded`.

But when the form includes files, it is encoded as `multipart/form-data`. You'll read about handling files in the next chapter.

	// Channel *must* be closed to signal the end of the stream.
	// If the request context is canceled, the stream will no longer process requests.
	// Requests sent cannot be used any further by the called.
	Requests chan<- []byte

	muxID uint64
	ctx   context.Context
}

// Send a payload to the remote server.
func (s *Stream) Send(b []byte) error {
	if s.Requests == nil {

      (d) If the Work includes a "NOTICE" text file as part of its
          distribution, then any Derivative Works that You distribute must
          include a readable copy of the attribution notices contained
          within such NOTICE file, excluding those notices that do not
          pertain to any part of the Derivative Works, in at least one
          of the following places: within a NOTICE text file distributed

      (d) If the Work includes a "NOTICE" text file as part of its
          distribution, then any Derivative Works that You distribute must
          include a readable copy of the attribution notices contained
          within such NOTICE file, excluding those notices that do not
          pertain to any part of the Derivative Works, in at least one
          of the following places: within a NOTICE text file distributed

          boolean haveBeenCalled;

          @Override
          public Integer computeNext() {
            if (haveBeenCalled) {
              throw new AssertionError("Should not have been called again");
            } else {
              haveBeenCalled = true;
              sneakyThrow(new SomeCheckedException());
              throw new AssertionError(); // unreachable
            }
          }