/**
   * Returns a value from this adapter.
   *
   * This must always return a value, though it doesn't necessarily need to consume data from
   * [reader]. For example, if the reader's peeked tag isn't readable by this adapter, it may return
   * a default value.
   *
   * If this does read a value, it starts with the tag and length, and reads an entire value,
   * including any potential composed values.
   *

# Classes as Dependencies { #classes-as-dependencies }

Before diving deeper into the **Dependency Injection** system, let's upgrade the previous example.

## A `dict` from the previous example { #a-dict-from-the-previous-example }

In the previous example, we were returning a `dict` from our dependency ("dependable"):

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

     * Gets the length of the first message in the pipe
     * @return the messageLength
     */
    public int getMessageLength() {
        return this.messageLength;
    }

    /**
     * Gets the data peeked from the pipe
     * @return the data
     */
    public byte[] getData() {
        return this.data;
    }

    /**
     * {@inheritDoc}
     *
     * @see Decodable#decode(byte[], int, int)
     */

</div>

That would work for most of the cases. 😎

You could use that command for example to start your **FastAPI** app in a container, in a server, etc.

## ASGI Servers { #asgi-servers }

Let's go a little deeper into the details.

FastAPI uses a standard for building Python web frameworks and servers called <abbr title="Asynchronous Server Gateway Interface">ASGI</abbr>. FastAPI is an ASGI web framework.

 * methods use {@link URL} parameters, they are usually not appropriate for HTTP or other
 * non-classpath resources.
 *
 * @author Chris Nokleberg
 * @author Ben Yu
 * @author Colin Decker
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
public final class Resources {
  private Resources() {}

  /**
   * Returns a {@link ByteSource} that reads from the given URL.
   *

import java.io.ByteArrayOutputStream;
import java.util.Random;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests for AbstractByteHasher.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class AbstractByteHasherTest extends TestCase {

  public void testBytes() {
    TestHasher hasher = new TestHasher(); // byte order insignificant here

import java.io.OutputStream;
import java.util.EnumSet;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests for the default implementations of {@code ByteSink} methods.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class ByteSinkTest extends IoTestCase {

  private final byte[] bytes = newPreFilledByteArray(10000);

  private TestByteSink sink;

  @Override

import java.io.OutputStream;
import java.util.EnumSet;
import org.jspecify.annotations.NullUnmarked;

/**
 * Tests for the default implementations of {@code ByteSink} methods.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class ByteSinkTest extends IoTestCase {

  private final byte[] bytes = newPreFilledByteArray(10000);

  private TestByteSink sink;

  @Override

import java.util.Objects;
import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;
import org.jspecify.annotations.Nullable;

/**
 * Tests for {@link Closer}.
 *
 * @author Colin Decker
 */
@NullUnmarked
public class CloserTest extends TestCase {

  private TestSuppressor suppressor;

  @Override
  protected void setUp() throws Exception {
    suppressor = new TestSuppressor();
  }

import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.CopyOnWriteArraySet;
import org.jspecify.annotations.Nullable;

/**
 * Registry of subscribers to a single event bus.
 *
 * @author Colin Decker
 */
final class SubscriberRegistry {

  /**
   * All registered subscribers, indexed by event type.
   *
   * <p>The {@link CopyOnWriteArraySet} values make it easy and relatively lightweight to get an