{* ../../docs_src/advanced_middleware/tutorial001.py hl[2,6] *}

## `TrustedHostMiddleware`

Enforces that all incoming requests have a correctly set `Host` header, in order to guard against HTTP Host Header attacks.

{* ../../docs_src/advanced_middleware/tutorial002.py hl[2,6:8] *}

The following arguments are supported:

    private Map<Object, MergeableMetadata> relatedMetadata = new ConcurrentHashMap<>();

    /**
     * @deprecated we want to use the artifact method only, and ensure artifact.file is set
     *             correctly.
     */
    @Deprecated
    public void deploy(
            String basedir,
            String finalName,
            Artifact artifact,
            ArtifactRepository deploymentRepository,

    @Inject
    private RepositorySystem repoSystem;

    @Inject
    private LegacySupport legacySupport;

    /** @deprecated we want to use the artifact method only, and ensure artifact.file is set correctly. */
    @Deprecated
    public void install(String basedir, String finalName, Artifact artifact, ArtifactRepository localRepository)
            throws ArtifactInstallationException {

          mapEntry("three", collectionOf(300)),
          mapEntry("four", collectionOf(-40)),
          mapEntry("five", collectionOf(5)));
    }

    // javac7 can't infer the type parameters correctly in samples()
    private static Collection<Integer> collectionOf(int item) {
      return ImmutableSet.of(item);
    }

    @Override
    public Map<String, Collection<Integer>> create(Object... elements) {

    JAVACMD="$JAVA_HOME/jre/sh/java"
  else
    JAVACMD="$JAVA_HOME/bin/java"

    if [ ! -x "$JAVACMD" ] ; then
      echo "The JAVA_HOME environment variable is not defined correctly, so Apache Maven cannot be started." >&2
      echo "JAVA_HOME is set to \"$JAVA_HOME\", but \"\$JAVA_HOME/bin/java\" does not exist." >&2
      exit 1
    fi
  fi
else

Create a function to be run as the background task.

It is just a standard function that can receive parameters.

It can be an `async def` or normal `def` function, **FastAPI** will know how to handle it correctly.

In this case, the task function will write to a file (simulating sending an email).

And as the write operation doesn't use `async` and `await`, we define the function with normal `def`:

public class DefaultProfileInjector implements ProfileInjector {

    private static final Map<Model, Map<List<Profile>, Model>> CACHE = Collections.synchronizedMap(new WeakHashMap<>());

    // In order for the weak hash map to work correctly, we must not hold any reference to
    // the model used as the key.  So we use a dummy model as a placeholder to indicate that
    // we want to store the model used as they key.

    private Properties requestProperties;

    /**
     * @deprecated without passing in the system properties, the SystemPropertiesProfileActivator will not work
     *             correctly in embedded environments.
     */
    @Deprecated
    public DefaultProfileManager(PlexusContainer container) {
        this(container, null);
    }

    /**

            }
            lifecyclesPrinted = true;
        }

        // If people are going to make their own lifecycles then we need to tell people how to namespace them correctly
        // so that they don't interfere with internally defined lifecycles.

        Map<String, Lifecycle> phaseToLifecycleMap = new HashMap<>();

        for (Lifecycle lifecycle : getLifeCycles()) {

for %%i in (java.exe) do set "JAVACMD=%%~$PATH:i"
goto checkJavaCmd

:javaHomeSet
set "JAVACMD=%JAVA_HOME%\bin\java.exe"

if not exist "%JAVACMD%" (
  echo The JAVA_HOME environment variable is not defined correctly, so Apache Maven cannot be started. >&2
  echo JAVA_HOME is set to "%JAVA_HOME%", but "%%JAVA_HOME%%\bin\java.exe" does not exist. >&2
  goto error
)

:checkJavaCmd
if not exist "%JAVACMD%" (