# Query-Parameter und String-Validierungen { #query-parameters-and-string-validations }

**FastAPI** ermöglicht es Ihnen, zusätzliche Informationen und Validierungen für Ihre Parameter zu deklarieren.

Nehmen wir diese Anwendung als Beispiel:

{* ../../docs_src/query_params_str_validations/tutorial001_py310.py hl[7] *}

 *   <li>Access to the session context used during processing</li>
 *   <li>Correlation of results with their initiating parameters</li>
 * </ul>
 *
 * @param <REQ> the type of Request that produced this result, ensuring type-safe
 *              access to the original request parameters
 *
 * @see Request
 * @since 4.0.0
 */
@Experimental
@Immutable
public interface Result<REQ extends Request<?>> {

	// E.g. "ldap.minio.io:636"
	ServerAddr string `json:"serverAddr"`

	// User DN search parameters
	UserDNSearchBaseDistName  string   `json:"userDNSearchBaseDN"`
	UserDNSearchBaseDistNames []string `json:"-"` // Generated field
	UserDNSearchFilter        string   `json:"userDNSearchFilter"`

	// Group search parameters
	GroupSearchBaseDistName  string   `json:"groupSearchBaseDN"`

   * {@code lexicographical(Collections.reverseOrder(comparator))} (consider how each would order
   * {@code [1]} and {@code [1, 1]}).
   */
  // Note: 90% of the time we don't add type parameters or wildcards that serve only to "tweak" the
  // desired return type. However, *nested* generics introduce a special class of problems that we
  // think tip it over into being worthwhile.

import org.junit.runners.Parameterized.Parameters;

/** Tests for an undirected {@link StandardMutableGraph}. */
@AndroidIncompatible
@RunWith(Parameterized.class)
@NullUnmarked
public final class StandardImmutableUndirectedGraphTest
    extends AbstractStandardUndirectedGraphTest {

  @Parameters(name = "allowsSelfLoops={0}")
  public static Collection<Object[]> parameters() {

        "paths": {
            "/": {
                "get": {
                    "summary": "Route With Extra Query Parameters",
                    "operationId": "route_with_extra_query_parameters__get",
                    "parameters": [
                        {
                            "required": False,
                            "schema": {

private
class MethodSignatureVisitor(private val asmLevel: Int) : BaseSignatureVisitor(asmLevel) {

    val parameters: MutableList<TypeSignatureVisitor> = ArrayList(1)

    val returnType = TypeSignatureVisitor(asmLevel)

    override fun visitParameterType(): SignatureVisitor =
        TypeSignatureVisitor(asmLevel).also { parameters.add(it) }

    override fun visitReturnType(): SignatureVisitor =
        returnType
}

func (l *List[T]) Len() int  { … }
</pre>

<h3 id="Type_parameter_declarations">Type parameter declarations</h3>

<p>
A type parameter list declares the <i>type parameters</i> of a generic function or type declaration.
The type parameter list looks like an ordinary <a href="#Function_types">function parameter list</a>
except that the type parameter names must all be present and the list is enclosed
in square brackets rather than parentheses

            },
            "/users/{user_id}": {
                "get": {
                    "summary": "Get User",
                    "operationId": "get_user_users__user_id__get",
                    "parameters": [
                        {
                            "required": True,
                            "schema": {"title": "User Id", "type": "string"},
                            "name": "user_id",

    return {"p": p.p}


@pytest.mark.parametrize(
    "path",
    ["/optional-str", "/model-optional-str"],
)
def test_optional_str_schema(path: str):
    assert app.openapi()["paths"][path]["get"]["parameters"] == [
        {
            "required": False,
            "schema": {
                "anyOf": [{"type": "string"}, {"type": "null"}],
                "title": "P",
            },
            "name": "p",