# 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] *}

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

First, create the main, top-level, **FastAPI** application, and its *path operations*:

{* ../../docs_src/sub_applications/tutorial001.py hl[3, 6:8] *}

### Sub-application { #sub-application }

Then, create your sub-application, and its *path operations*.

    new ForwardingWrapperTester()
        .testForwarding(
            Sub.class,
            new Function<Sub, Sub>() {
              @Override
              public Sub apply(Sub sub) {
                return new ForwardingSub(sub);
              }
            });
  }

  interface Base {
    CharSequence getId();
  }

  interface Sub extends Base {
    @Override
    String getId();
  }

    new ForwardingWrapperTester()
        .testForwarding(
            Sub.class,
            new Function<Sub, Sub>() {
              @Override
              public Sub apply(Sub sub) {
                return new ForwardingSub(sub);
              }
            });
  }

  interface Base {
    CharSequence getId();
  }

  interface Sub extends Base {
    @Override
    String getId();
  }

## Details { #details }

The first `"/static"` refers to the sub-path this "sub-application" will be "mounted" on. So, any path that starts with `"/static"` will be handled by it.

The `directory="static"` refers to the name of the directory that contains your static files.

The `name="static"` gives it a name that can be used internally by **FastAPI**.

		}
	}
	return nil
}

// Help - return sub-system level help
type Help struct {
	SubSys          string         `json:"subSys"`
	Description     string         `json:"description"`
	MultipleTargets bool           `json:"multipleTargets"`
	KeysHelp        config.HelpKVS `json:"keysHelp"`
}

// GetHelp - returns help for sub-sys, a key for a sub-system or all the help.

        testBuffer[27] = 0x05;
        SMBUtil.writeInt4(21, testBuffer, 28); // sub-authority 1
        SMBUtil.writeInt4(1000, testBuffer, 32); // sub-authority 2
        SMBUtil.writeInt4(2000, testBuffer, 36); // sub-authority 3

        // Group SID with 2 sub-authorities
        testBuffer[44] = 0x01; // revision
        testBuffer[45] = 0x02; // sub-authority count
        testBuffer[46] = 0x00; // identifier authority

# Including WSGI - Flask, Django, others { #including-wsgi-flask-django-others }

You can mount WSGI applications as you saw with [Sub Applications - Mounts](sub-applications.md){.internal-link target=_blank}, [Behind a Proxy](behind-a-proxy.md){.internal-link target=_blank}.

For that, you can use the `WSGIMiddleware` and use it to wrap your WSGI application, for example, Flask, Django, etc.

## Using `WSGIMiddleware` { #using-wsgimiddleware }

        testBuffer[8] = 0x01; // Revision
        testBuffer[9] = 0x01; // Sub-authority count
        testBuffer[10] = 0x00; // Identifier authority
        testBuffer[11] = 0x00;
        testBuffer[12] = 0x00;
        testBuffer[13] = 0x00;
        testBuffer[14] = 0x00;
        testBuffer[15] = 0x01;
        testBuffer[16] = 0x00; // Sub-authority
        testBuffer[17] = 0x00;
        testBuffer[18] = 0x00;

Deshalb, um ID-Kollisionen zu vermeiden, könnten Sie beim Erstellen des JWT-Tokens für den Benutzer, dem Wert des `sub`-Schlüssels ein Präfix, z. B. `username:` voranstellen. In diesem Beispiel hätte der Wert von `sub` also auch `username:johndoe` sein können.

Der wesentliche Punkt ist, dass der `sub`-Schlüssel in der gesamten Anwendung eine eindeutige Kennung haben sollte, und er sollte ein String sein.

## Es testen