# 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] *}

Wenn im Request ein Query-Parameter enthalten war, wird dieser in einem Hintergrundtask in das Log geschrieben.

Und dann schreibt ein weiterer Hintergrundtask, der in der *Pfadoperation-Funktion* erstellt wird, eine Nachricht unter Verwendung des Pfad-Parameters `email`.

## Technische Details { #technical-details }

# Body - Multiple Parameters { #body-multiple-parameters }

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters { #mix-path-query-and-body-parameters }

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

# Query Parameter Models { #query-parameter-models }

If you have a group of **query parameters** that are related, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

# Query Parameters and String Validations { #query-parameters-and-string-validations }

**FastAPI** allows you to declare additional information and validation for your parameters.

Let's take this application as example:

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

# Path Parameters and Numeric Validations { #path-parameters-and-numeric-validations }

In the same way that you can declare more validations and metadata for query parameters with `Query`, you can declare the same type of validations and metadata for path parameters with `Path`.

## Import `Path` { #import-path }

First, import `Path` from `fastapi`, and import `Annotated`:

{* ../../docs_src/path_params_numeric_validations/tutorial001_an_py310.py hl[1,3] *}

{* ../../docs_src/body/tutorial002_py310.py *}

## Request body + path parameters { #request-body-path-parameters }

You can declare path parameters and request body at the same time.

**FastAPI** will recognize that the function parameters that match path parameters should be **taken from the path**, and that function parameters that are declared to be Pydantic models should be **taken from the request body**.

import java.util.Arrays;

/**
 * Entity class representing a request parameter with a name and associated values.
 * This class encapsulates HTTP request parameters that can have multiple values,
 * such as query parameters, form parameters, or other request-related data.
 *
 * <p>This class is immutable and thread-safe. Once created, the parameter name
 * and values cannot be modified.</p>
 *
 */
public class RequestParameter {

                "The parameters " + format(parameters) + " for goal " + mojo.getRoleHint() + " are missing or invalid");

        this.mojo = mojo;

        this.parameters = parameters;
    }

    private static String format(List<Parameter> parameters) {
        StringBuilder buffer = new StringBuilder(128);
        if (parameters != null) {
            for (Parameter parameter : parameters) {

    }

    /**
     * Stores a parameter value with the specified key.
     *
     * @param key the parameter key, must not be null
     * @param value the parameter value, may be null
     */
    public void put(final String key, final Object value) {
        params.put(key, value);
    }

    /**
     * Retrieves a parameter value by key.
     *
     * @param key the parameter key to look up