If you look at it, *path operation functions* are declared to be used whenever a *path* and *operation* matches, and then **FastAPI** takes care of calling the function with the correct parameters, extracting the data from the request.

Actually, all (or most) of the web frameworks work in this same way.

You never call those functions directly. They are called by your framework (in this case, **FastAPI**).

        with:
          # For discussion, see the first setup-java block.
          # The publish-snapshot workflow doesn't run tests, so we don't have to care which version Maven would select for that step.
          java-version: 25
          distribution: 'temurin'
          cache: 'maven'
          server-id: central
          server-username: CI_DEPLOY_USERNAME

## Mounting a **FastAPI** application { #mounting-a-fastapi-application }

"Mounting" means adding a completely "independent" application in a specific path, that then takes care of handling everything under that path, with the _path operations_ declared in that sub-application.

### Top-level application { #top-level-application }

///

### What is "Mounting" { #what-is-mounting }

"Mounting" means adding a complete "independent" application in a specific path, that then takes care of handling all the sub-paths.

This is different from using an `APIRouter` as a mounted application is completely independent. The OpenAPI and docs from your main application won't include anything from the mounted application, etc.

It brings the same **developer experience** of building apps with FastAPI to **deploying** them to the cloud. 🎉

It will also take care of most of the things you would need when deploying an app, like:

* HTTPS
* Replication, with autoscaling based on requests
* etc.

           *
           * ...when we build with JDK 22 and run under JDK 8.
           */
          || info.getName().contains("MultimapsTest")
      /*
       * Luckily, we don't care about analyzing tests at all. We'd skip them all if we could do so
       * trivially, but it's enough to skip these ones.
       */
      ) {
        continue;
      }
      Class<?> clazz = info.load();
      try {

# Sub-dependencies { #sub-dependencies }

You can create dependencies that have **sub-dependencies**.

They can be as **deep** as you need them to be.

**FastAPI** will take care of solving them.

## First dependency "dependable" { #first-dependency-dependable }

You could create a first dependency ("dependable") like:

{* ../../docs_src/dependencies/tutorial005_an_py310.py hl[8:9] *}

Most of the standard headers are separated by a "hyphen" character, also known as the "minus symbol" (`-`).

But a variable like `user-agent` is invalid in Python.

So, by default, `Header` will convert the parameter names characters from underscore (`_`) to hyphen (`-`) to extract and document the headers.

			}...) {
				return 0, err
			}
		}

		eof := err == io.EOF || err == io.ErrUnexpectedEOF
		if n == 0 && total != 0 {
			// Reached EOF, nothing more to be done.
			break
		}

		// We take care of the situation where if n == 0 and total == 0 by creating empty data and parity files.
		blocks, err = e.EncodeData(ctx, buf[:n])
		if err != nil {
			return 0, err
		}

        if (value instanceof Entity) {
            data.register(key, BeanUtil.copyBeanToNewMap(value));
        } else {
            if (value instanceof final Collection<?> coll && !coll.isEmpty()) {
                // care performance for List that the most frequent pattern
                final Object first = coll instanceof List<?> ? ((List<?>) coll).get(0) : coll.iterator().next();
                if (first instanceof Entity) {