# Dependencies

**FastAPI** has a very powerful but intuitive **<abbr title="also known as components, resources, providers, services, injectables">Dependency Injection</abbr>** system.

It is designed to be very simple to use, and to make it very easy for any developer to integrate other components with **FastAPI**.

## What is "Dependency Injection"

import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * Base class for services that can implement {@link #startUp}, {@link #run} and {@link #shutDown}
 * methods. This class uses a single thread to execute the service; consider {@link AbstractService}
 * if you would like to manage any threading manually.
 *
 * @author Jesse Wilson
 * @since 1.0
 */

     *       module-path, but is also compatible with placement on the class-path. Compatibility can
     *       be achieved, for example, by repeating in the {@code META-INF/services/} directory the services
     *       that are declared in the {@code module-info.class} file. In that case, the path type can be chosen
     *       by the plugin.</li>

 * processing by providing a means to transport information that cannot be (easily) extracted from the model itself.
 *
 * @deprecated use {@link org.apache.maven.api.services.ModelBuilder} instead
 */
@Deprecated(since = "4.0.0")
class ModelData {
    private final Source source;

    private final Model model;

    private String groupId;

    private String artifactId;

 * thrown or a simple string message. In addition, a problem carries a hint about its source, e.g. the settings file
 * that exhibits the problem.
 *
 * @deprecated since 4.0.0, use {@link org.apache.maven.api.services.SettingsBuilder} instead
 */
@Deprecated(since = "4.0.0")
public class DefaultSettingsProblem implements SettingsProblem {

    private final String source;

    private final int lineNumber;

 */
package org.apache.maven.api.cli;

import java.io.IOException;

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;
import org.apache.maven.api.services.MessageBuilderFactory;

/**
 * Defines the contract for parsing Maven command-line arguments and creating an InvokerRequest.
 * This interface is responsible for interpreting the command-line input and constructing

import org.apache.maven.api.annotations.Provider;

/**
 * Represents a dependency node within a Maven project's dependency collector.
 *
 * @since 4.0.0
 * @see org.apache.maven.api.services.DependencyResolverResult#getRoot()
 */
@Experimental
@Immutable
@Provider
public interface Node {

    /**
     * @return artifact for this node
     */
    @Nullable
    Artifact getArtifact();

 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.maven.api.services.xml;

import java.io.OutputStream;
import java.io.Writer;
import java.nio.file.Path;
import java.util.function.Function;

import org.apache.maven.api.annotations.Experimental;

import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * @deprecated use {@link org.apache.maven.api.services.ModelBuilder} instead
 */
@Deprecated(since = "4.0.0")
class Graph {

    final Map<String, Set<String>> graph = new LinkedHashMap<>();

import org.apache.maven.model.profile.ProfileActivationContext;

/**
 * Determines whether a profile should be activated.
 *
 * @deprecated use {@link org.apache.maven.api.services.ModelBuilder} instead
 */
@Deprecated(since = "4.0.0")
public interface ProfileActivator {

    /**
     * Determines whether the specified profile is active in the given activator context.
     *