try {
                    artifact = artifact.setFile(ProjectClasspathTestType.getFileForClasspathResource(
                            ProjectClasspathTestType.DIR + "transitive-" + scope + "-dep.xml"));
                    result.setArtifact(artifact);
                } catch (FileNotFoundException | URISyntaxException e) {
                    throw new IllegalStateException("Missing test POM for " + artifact, e);

* data validation
* data serialization
* data documentation, etc.

This works the same way as with Pydantic models. And it is actually achieved in the same way underneath, using Pydantic.

/// info

Keep in mind that dataclasses can't do everything Pydantic models can do.

So, you might still need to use Pydantic models.

* Editor ondersteuning, inclusief:
    * Code aanvulling.
    * Type validatie.
* Validatie van data:
    * Automatische en duidelijke foutboodschappen wanneer de data ongeldig is.
    * Validatie zelfs voor diep geneste JSON objecten.
* <abbr title="ook bekend als: serialisatie, parsing, marshalling">Conversie</abbr> van invoergegevens: afkomstig van het netwerk naar Python-data en -types. Zoals:
    * JSON.
    * Pad parameters.

* You can then further modify the `response` before returning it.

{* ../../docs_src/middleware/tutorial001.py hl[8:9,11,14] *}

/// tip

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the 'X-' prefix</a>.

Just use any kind of model, any kind of class, any kind of database that you need for your application. **FastAPI** has you covered with the dependency injection system.

## Code size { #code-size }

This example might seem verbose. Keep in mind that we are mixing security, data models, utility functions and *path operations* in the same file.

But here's the key point.

The security and dependency injection stuff is written once.

Including how to handle lifespan state that can be used in other areas of your code.

///

## Sub Applications { #sub-applications }

In many cases it's not very obvious how environment variables would be useful and applicable right away. But they keep showing up in many different scenarios when you are developing, so it's good to know about them.

 * number of streams, dynamically configured with `SETTINGS_MAX_CONCURRENT_STREAMS`. A connection
 * currently carrying zero streams is an idle stream. We keep it alive because reusing an existing
 * connection is typically faster than establishing a new one.
 *
 * When a single logical call requires multiple streams due to redirects or authorization

  private static void executeListener(Runnable runnable, Executor executor) {
    try {
      executor.execute(runnable);
    } catch (Exception e) { // sneaky checked exception
      // Log it and keep going -- bad runnable and/or executor. Don't punish the other runnables if
      // we're given a bad one. We only catch Exception because we want Errors to propagate up.
      log.get()
          .log(

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keep intact all notices stating that this License and any
non-permissive terms added in accord with section 7 apply to the code;
keep intact all notices of the absence of any warranty; and give all
recipients a copy of this License along with the Program.