For production you would use `fastapi run` instead. 🚀

Internally, **FastAPI CLI** uses <a href="https://www.uvicorn.org" class="external-link" target="_blank">Uvicorn</a>, a high-performance, production-ready, ASGI server. 😎

## `fastapi dev` { #fastapi-dev }

Running `fastapi dev` initiates development mode.

 *
 * <p>The tested methods and constructors are invoked -- each time with one parameter being null and
 * the rest not null -- and the test fails if no expected exception is thrown. {@code
 * NullPointerTester} uses best effort to pick non-null default values for many common JDK and Guava
 * types, and also for interfaces and public classes that have public parameter-less constructors.

import okhttp3.internal.okHttpName
import okhttp3.internal.threadFactory

/**
 * A set of worker threads that are shared among a set of task queues.
 *
 * Use [INSTANCE] for a task runner that uses daemon threads. There is not currently a shared
 * instance for non-daemon threads.
 *
 * The task runner is also responsible for releasing held threads when the library is unloaded.

import static java.lang.Math.min;

import com.google.common.annotations.GwtCompatible;
import java.util.Map;
import org.jspecify.annotations.Nullable;

/**
 * A {@link UnicodeEscaper} that uses an array to quickly look up replacement characters for a given
 * code point. An additional safe range is provided that determines whether code points without

@Deprecated
@Beta
@GwtCompatible
public abstract class TreeTraverser<T> {
  /** Constructor for use by subclasses. */
  public TreeTraverser() {}

  /**
   * Returns a tree traverser that uses the given function to navigate from a node to its children.
   * This is useful if the function instance already exists, or so that you can supply a lambda

   * href="https://docs.oracle.com/javase/tutorial/java/generics/genTypeInference.html#type-inference-instantiation">"diamond"
   * syntax</a>. One caveat to this is that the {@code TreeSet} constructor uses a null {@code
   * Comparator} to mean "natural ordering," whereas this factory rejects null. Clean your code
   * accordingly.
   *
   * @param comparator the comparator to use to sort the set

        // Test clearing a flag that is not set
        message.setFlags(0b1000);
        message.setFlag(0b0001, false);
        assertEquals(0b1000, message.getFlags(), "Clearing an unset flag should not change other flags.");
    }

    @Test
    void testReadULong() {
        // Test readULong with various values
        byte[] data = new byte[8];

Webargs is a tool that was made to provide that on top of several frameworks, including Flask.

It uses Marshmallow underneath to do the data validation. And it was created by the same developers.

It's a great tool and I have used it a lot too, before having **FastAPI**.

/// info

import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * Base class for services that can implement {@link #startUp}, {@link #run} and {@link #shutDown}
 * methods. This class uses a single thread to execute the service; consider {@link AbstractService}
 * if you would like to manage any threading manually.
 *
 * @author Jesse Wilson
 * @since 1.0
 */
@GwtIncompatible
@J2ktIncompatible

 *       complicate debugging, lead to unintentional reentrant calls, and force apps to eagerly
 *       initialize all possible subscribers at startup time.
 *   <li>It uses reflection in ways that break when code is processed by optimizers/minimizers like
 *       <a href="https://developer.android.com/studio/build/shrink-code">R8 and Proguard</a>.