## 掛載一個 **FastAPI** 應用程式 { #mounting-a-fastapi-application }

「掛載」是指在某個特定路徑下加入一個完全「獨立」的應用程式，之後該應用程式會負責處理該路徑底下的一切，使用該子應用程式中宣告的*路徑操作（path operation）*。

### 頂層應用程式 { #top-level-application }

先建立主（頂層）**FastAPI** 應用程式以及它的*路徑操作*：

{* ../../docs_src/sub_applications/tutorial001_py310.py hl[3, 6:8] *}

### 子應用程式 { #sub-application }

接著，建立你的子應用程式及其*路徑操作*。

這個子應用程式就是另一個標準的 FastAPI 應用，但這個會被「掛載」：

    private static final String FESS_OVERRIDE_CONF_PATH = "FESS_OVERRIDE_CONF_PATH";

    /** Environment variable name for specifying the application type */
    private static final String FESS_APP_TYPE = "FESS_APP_TYPE";

    /** Constant value representing Docker application type */
    private static final String FESS_APP_DOCKER = "docker";

    /**
     * Protected constructor to prevent instantiation of this utility class.

In many cases your application could need some external settings or configurations, for example secret keys, database credentials, credentials for email services, etc.

Most of these settings are variable (can change), like database URLs. And many could be sensitive, like secrets.

For this reason it's common to provide them in environment variables that are read by the application.

/// tip

///

## Separating tests { #separating-tests }

In a real application, you probably would have your tests in a different file.

And your **FastAPI** application might also be composed of several files/modules, etc.

                                "content": {"application/json": {"schema": {}}},
                            },
                            "422": {
                                "description": "Validation Error",
                                "content": {
                                    "application/json": {
                                        "schema": {

That's what would happen to a third party application that tried to access one of these *path operations* with a token provided by a user, depending on how many permissions the user gave the application.

## About third party integrations { #about-third-party-integrations }

In this example we are using the OAuth2 "password" flow.

This is appropriate when we are logging in to our own application, probably with our own frontend.

        return request(Method.GET, path).header("Content-Type", "application/json");
    }

    /**
     * Creates a POST request for the specified path.
     * @param path the request path
     * @return the configured CurlRequest
     */
    public CurlRequest post(final String path) {
        return request(Method.POST, path).header("Content-Type", "application/json");
    }

    /**

post() {
    local endpoint="$1"
    local data="$2"

    local response=$(curl -X POST \
        -H "Authorization: token $GITHUB_TOKEN" \
        -H "Accept: application/vnd.github.v3+json" \
        -H "Content-Type: application/json" \
        "https://api.github.com/repos/gradle/gradle$endpoint" \
        -d "$data" \
        -w "\n%{http_code}" \
        2>/dev/null)

    assertThat(MediaType.parse("text/plain").type()).isEqualTo("text");
    assertThat(MediaType.parse("application/atom+xml; charset=utf-8").type())
        .isEqualTo("application");
  }

  public void testGetSubtype() {
    assertThat(MediaType.parse("text/plain").subtype()).isEqualTo("plain");
    assertThat(MediaType.parse("application/atom+xml; charset=utf-8").subtype())
        .isEqualTo("atom+xml");
  }

                                "content": {"application/json": {"schema": {}}},
                            },
                            "422": {
                                "description": "Validation Error",
                                "content": {
                                    "application/json": {
                                        "schema": {