并且，可以按需声明任意**深度**的子依赖项嵌套层级。

**FastAPI** 负责处理解析不同深度的子依赖项。

## 第一层依赖项 “dependable” { #first-dependency-dependable }

你可以创建一个第一层依赖项（“dependable”），如下：

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

这段代码声明了类型为 `str` 的可选查询参数 `q`，然后返回这个查询参数。

这个函数很简单（不过也没什么用），但却有助于让我们专注于了解子依赖项的工作方式。

## 第二层依赖项，“dependable”和“dependant” { #second-dependency-dependable-and-dependant }

  <packaging>pom</packaging>

  <name>Simple Unit Test Parent</name>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>ut.simple</groupId>
        <artifactId>dependency</artifactId>
        <version>1.0</version>
      </dependency>
    </dependencies>
  </dependencyManagement>

    /**
     * Creates a new project dependency graph from the specified graph.
     *
     * @param projectDependencyGraph The project dependency graph to create a sub view from, must not be {@code null}.
     * @param whiteList The projects on which the dependency view should focus, must not be {@code null}.
     */
    FilteredProjectDependencyGraph(

### `OAuth2PasswordRequestForm` { #oauth2passwordrequestform }

First, import `OAuth2PasswordRequestForm`, and use it as a dependency with `Depends` in the *path operation* for `/token`:

{* ../../docs_src/security/tutorial003_an_py310.py hl[4,78] *}

`OAuth2PasswordRequestForm` is a class dependency that declares a form body with:

* The `username`.
* The `password`.

- **Maven 3.6+** or **Gradle 7+** for build management
- **Optional**: SLF4J or Commons Logging for logging support

### Maven Dependency
```xml
<dependency>
    <groupId>org.codelibs</groupId>
    <artifactId>corelib</artifactId>
    <version>0.7.0</version>
</dependency>
```

### Gradle Dependency
```gradle
implementation 'org.codelibs:corelib:0.7.0'
```

## 📖 Usage Examples

### Bean Utilities
```java

  <artifactId>maven-api-xml</artifactId>
  <name>Maven 4 API :: XML</name>
  <description>Maven 4 API - Immutable XML.</description>

  <dependencies>
    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-api-annotations</artifactId>
    </dependency>
  </dependencies>

    <artifactId>maven-api</artifactId>
    <version>4.1.0-SNAPSHOT</version>
  </parent>

  <artifactId>maven-api-di</artifactId>
  <name>Maven 4 API :: Dependency Injection</name>
  <description>Maven 4 API - Dependency Injection</description>

  <properties>
    <maven.compiler.proc>none</maven.compiler.proc>
  </properties>

  <version>1.0-SNAPSHOT</version>
  <name>simple-project</name>
  <url>http://maven.apache.org</url>
  <dependencies>
      <dependency>
          <groupId>org.junit.jupiter</groupId>
          <artifactId>junit-jupiter-api</artifactId>
          <version>5.14.0</version>
          <scope>test</scope>
      </dependency>
  </dependencies>
  <properties>
    <environment>development</environment>
  </properties>

    This will test if the module validator recognized that this dependency with classifier
    is not the same as the module itself.
  </description>
  <dependencies>
    <dependency>
      <groupId>com.example.group</groupId>
      <artifactId>testvalidpom</artifactId>
      <version>0.0.1-SNAPSHOT</version>
      <classifier>linux</classifier>
    </dependency>
  </dependencies>

  <description>
    This will test if the module validator recognized that this
    dependency is the same as the module itself.
  </description>
  <dependencies>
    <dependency>
      <groupId>com.example.group</groupId>
      <artifactId>testinvalidpom</artifactId>
      <version>0.0.1-SNAPSHOT</version>
    </dependency>
  </dependencies>