* thus a motivated caller may be able to expose the reference to another thread that would then
   * call cancel() and be unable to cancel the delegate.
   * There are a number of ways to solve this, none of which are very pretty, and it is currently
   * believed to be a purely theoretical problem (since the other actions should supply sufficient
   * write-barriers).
   */

  @LazyInit private @Nullable ListenableFuture<V> delegateRef;

/*
 * Copyright 2012-2025 CodeLibs Project and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

/*
 * Copyright 2012-2025 CodeLibs Project and the Others.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

## FastAPI Experts

The people that help others the most in GitHub Discussions can become [**FastAPI Experts**](./fastapi-people.md#fastapi-experts){.internal-link target=_blank}.

This is normally the best way to contribute to the project.

## External Contributions

External contributions are very welcome and appreciated, including answering questions, submitting PRs, etc. 🙇‍♂️

$ export MY_NAME="Wade Wilson"

// Then you could use it with other programs, like
$ echo "Hello $MY_NAME"

Hello Wade Wilson
```

</div>

////

//// tab | Windows PowerShell

<div class="termy">

```console
// Create an env var MY_NAME
$ $Env:MY_NAME = "Wade Wilson"

// Use it with other programs, like
$ echo "Hello $Env:MY_NAME"

Hello Wade Wilson
```

</div>

            return false;
        if (getClass() != obj.getClass())
            return false;
        RequestData other = (RequestData) obj;
        return method == other.method && Objects.equals(url, other.url)
                && Float.floatToIntBits(weight) == Float.floatToIntBits(other.weight);
    }

    /**
     * Returns a string representation of this object.
     * @return A string representation.

        assertFalse(crawlerEngineClient.equals(null));
        assertFalse(crawlerEngineClient.equals("string"));

        CrawlerEngineClient other = new CrawlerEngineClient();
        // Different instances should not be equal by default
        assertFalse(crawlerEngineClient.equals(other));
    }

    // Test getClass method
    public void test_getClass() {
        // Test that getClass returns the correct class

It is designed to be very simple to use, and to make it very easy for any developer to integrate other components with **FastAPI**.

## What is "Dependency Injection" { #what-is-dependency-injection }

**"Dependency Injection"** means, in programming, that there is a way for your code (in this case, your *path operation functions*) to declare things that it requires to work and use: "dependencies".

    * String (`str`) fields, defining min and max lengths.
    * Numbers (`int`, `float`) with min and max values, etc.

* Validation for more exotic types, like:
    * URL.
    * Email.
    * UUID.
    * ...and others.

All the validation is handled by the well-established and robust **Pydantic**.

### Security and authentication { #security-and-authentication }

# Custom Response - HTML, Stream, File, others { #custom-response-html-stream-file-others }

By default, **FastAPI** will return the responses using `JSONResponse`.

You can override it by returning a `Response` directly as seen in [Return a Response directly](response-directly.md){.internal-link target=_blank}.