Interceptors
============

Interceptors are a powerful mechanism that can monitor, rewrite, and retry calls. Here's a simple interceptor that logs the outgoing request and the incoming response.

```java
class LoggingInterceptor implements Interceptor {
  @Override public Response intercept(Interceptor.Chain chain) throws IOException {
    Request request = chain.request();

    long t1 = System.nanoTime();

## Declaring types { #declaring-types }

You just saw the main place to declare type hints. As function parameters.

This is also the main place you would use them with **FastAPI**.

### Simple types { #simple-types }

You can declare all the standard Python types, not only `str`.

You can use, for example:

* `int`
* `float`
* `bool`
* `bytes`

# Primeros Pasos

El archivo FastAPI más simple podría verse así:

{* ../../docs_src/first_steps/tutorial001.py *}

Copia eso en un archivo `main.py`.

Ejecuta el servidor en vivo:

<div class="termy">

```console
$ <font color="#4E9A06">fastapi</font> dev <u style="text-decoration-style:single">main.py</u>
<font color="#3465A4">INFO    </font> Using path <font color="#3465A4">main.py</font>

                <arg>--add-reads=com.google.common.testlib=ALL-UNNAMED</arg>
                <!-- https://errorprone.info/docs/installation#maven -->
                <arg>-XDcompilePolicy=simple</arg>
                <arg>-Xlint:-removal</arg>
                <arg>-Xlint:-options</arg>
              </compilerArgs>
              <multiReleaseOutput>true</multiReleaseOutput>
            </configuration>

                <arg>--add-reads=com.google.common.testlib=ALL-UNNAMED</arg>
                <!-- https://errorprone.info/docs/installation#maven -->
                <arg>-XDcompilePolicy=simple</arg>
                <arg>-Xlint:-removal</arg>
                <arg>-Xlint:-options</arg>
              </compilerArgs>
              <multiReleaseOutput>true</multiReleaseOutput>
            </configuration>

    builder.setSafeRange(' ', '~');
    assertThat(builder.build().escape("The Quick Brown Fox!")).isEqualTo("The_Quick_Brown_Fox_");
  }

  public void testBuilderCreatesIndependentEscapers() {
    // Set up a simple builder and create the first escaper.
    Escapers.Builder builder = Escapers.builder();
    builder.setSafeRange('a', 'z');
    builder.setUnsafeReplacement("X");
    builder.addEscape(' ', "_");

    public void run() {
      run = true;
    }
  }

  private static class TestCallable implements Callable<String> {
    @Override
    public String call() {
      return "foo";
    }
  }

  /** Simple same thread listening executor service that doesn't handle shutdown. */
  private static class TestListeningExecutorService extends AbstractListeningExecutorService {

    @Override
    public void execute(Runnable runnable) {

    public void run() {
      run = true;
    }
  }

  private static class TestCallable implements Callable<String> {
    @Override
    public String call() {
      return "foo";
    }
  }

  /** Simple same thread listening executor service that doesn't handle shutdown. */
  private static class TestListeningExecutorService extends AbstractListeningExecutorService {

    @Override
    public void execute(Runnable runnable) {

 * it delegates to other components that potentially encounter problems. Then, the problem reporter can focus on
 * providing a simple error message, leaving the donkey work of creating a nice model problem to this component.
 *
 */
public interface ModelProblemCollector {

    ProblemCollector<ModelProblem> getProblemCollector();

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import org.jspecify.annotations.Nullable;

/**
 * Implementation of {@link ImmutableList} backed by a simple array.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@SuppressWarnings("serial") // uses writeReplace(), not default serialization
final class RegularImmutableList<E> extends ImmutableList<E> {