### Injeção de dependência { #dependency-injection }

FastAPI inclui um sistema de <abbr title='também conhecido como "components", "resources", "services", "providers"'><strong>injeção de dependência</strong></abbr> extremamente fácil de usar, mas extremamente poderoso.

* Mesmo dependências podem ter dependências, criando uma hierarquia ou **"grafo" de dependências**.

 * your HTTP calls. This is because each client holds its own connection pool and thread pools.
 * Reusing connections and threads reduces latency and saves memory. Conversely, creating a client
 * for each request wastes resources on idle pools.
 *
 * Use `new OkHttpClient()` to create a shared instance with the default settings:
 *
 * ```java
 * // The singleton HTTP client.
 * public final OkHttpClient client = new OkHttpClient();
 * ```

### Внедрение зависимостей { #dependency-injection }

FastAPI включает в себя чрезвычайно простую в использовании, но чрезвычайно мощную систему <abbr title='известную как: "components", "resources", "services", "providers"'><strong>Внедрения зависимостей</strong></abbr>.

* Даже зависимости могут иметь зависимости, создавая иерархию или **«граф» зависимостей**.
* Всё **автоматически обрабатывается** фреймворком.

  }

  private void doExtensiveTest(String resourceName) throws IOException {
    Splitter splitter = Splitter.on(CharMatcher.whitespace());
    URL url = getClass().getResource(resourceName);
    for (String line : Resources.readLines(url, UTF_8)) {
      Iterator<String> iterator = splitter.split(line).iterator();
      String input = iterator.next();
      String expectedOutput = iterator.next();
      assertFalse(iterator.hasNext());

	if !r.contentHash.Type.IsSet() || !r.contentHash.Valid() {
		return nil
	}
	return &r.contentHash
}

var _ io.Closer = (*Reader)(nil) // compiler check

// Close and release resources.

```
~ mc admin config set alias/ scanner
KEY:

}

/**
 * We have some "shared" host where a Linux build agent and a Windows build agent
 * both run on the same bare metal. Some builds require exclusive access to the
 * hardware resources (e.g. performance test).
 */
fun Requirements.requiresNotSharedHost() {
    doesNotContain("agent.host.type", "shared")
}

/**
 * This is an undocumented location that forbids anonymous access.

    * Cookies, 等等。

加上来自 Starlette（包括 **session cookie**）的所有安全特性。

所有的这些都是可复用的工具和组件，可以轻松与你的系统，数据仓库，关系型以及 NoSQL 数据库等等集成。



### 依赖注入

FastAPI 有一个使用非常简单，但是非常强大的<abbr title='也叫做 "components", "resources", "services", "providers"'><strong>依赖注入</strong></abbr>系统。

* 甚至依赖也可以有依赖，创建一个层级或者**“图”依赖**。
* 所有**自动化处理**都由框架完成。
* 所有的依赖关系都可以从请求中获取数据，并且**增加了路径操作**约束和自动文档生成。
* 即使在依赖项中被定义的*路径操作* 也会**自动验证**。

 *
 * <p>{@link #setDefault} allows subclasses to specify default values for types.
 *
 * <p>This class incurs IO because it scans the classpath and reads classpath resources.
 *
 * @author Ben Yu
 * @since 14.0
 */
// TODO: Switch to JUnit 4 and use @Parameterized and @BeforeClass
// Note: @Test annotations are deliberate, as some subclasses specify @RunWith(JUnit4).

class DefaultModelValidatorTest {

    private ModelValidator validator;

    private Model read(String pom) throws Exception {
        String resource = "/poms/validation/" + pom;
        try (InputStream is = getClass().getResourceAsStream(resource)) {
            assertNotNull(is, "missing resource: " + resource);
            return new Model(new MavenStaxReader().read(is));
        }
    }