# Templates { #templates }

You can use any template engine you want with **FastAPI**.

A common choice is Jinja2, the same one used by Flask and other tools.

There are utilities to configure it easily that you can use directly in your **FastAPI** application (provided by Starlette).

## Install dependencies { #install-dependencies }

This can be very useful for setting up **resources** that you need to use for the whole app, and that are **shared** among requests, and/or that you need to **clean up** afterwards. For example, a database connection pool, or loading a shared machine learning model.

## Use Case { #use-case }

Let's start with an example **use case** and then see how to solve it with this.

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   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

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      "License" shall mean the terms and conditions for use, reproduction,
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      "Licensor" shall mean the copyright owner or entity authorized by

                           Version 2.0, January 2004
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   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

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      "License" shall mean the terms and conditions for use, reproduction,
      and distribution as defined by Sections 1 through 9 of this document.

      "Licensor" shall mean the copyright owner or entity authorized by

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   TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION

   1. Definitions.

      "License" shall mean the terms and conditions for use, reproduction,
      and distribution as defined by Sections 1 through 9 of this document.

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# Response Headers { #response-headers }

## Use a `Response` parameter { #use-a-response-parameter }

You can declare a parameter of type `Response` in your *path operation function* (as you can do for cookies).

And then you can set headers in that *temporal* response object.

{* ../../docs_src/response_headers/tutorial002.py hl[1, 7:8] *}

And then you can return any object you need, as you normally would (a `dict`, a database model, etc).

 *
 * @deprecated since 4.0.0, use {@link org.apache.maven.api.services} instead
 */
@Deprecated(since = "4.0.0")
public class FileSource implements Source {
    private final Path path;

    private final int hashCode;

    /**
     * Creates a new source backed by the specified file.
     *
     * @param file The file, must not be {@code null}.
     * @deprecated Use {@link #FileSource(Path)} instead.
     */