# Background Tasks - `BackgroundTasks`

You can declare a parameter in a *path operation function* or dependency function with the type `BackgroundTasks`, and then you can use it to schedule the execution of background tasks after the response is sent.

You can import it directly from `fastapi`:

```python
from fastapi import BackgroundTasks
```

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

import javax.inject.Named;
import javax.inject.Singleton;

import java.io.IOException;
import java.io.Reader;
import java.io.Writer;
import java.nio.file.Files;
import java.nio.file.Path;

import java.util.Set;

import org.apache.maven.MavenExecutionException;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.project.MavenProject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Utility class to extract {@link MavenProject} from the project graph during the execution phase based on optional or
 * required selectors.
 */
public final class ProjectSelector {

# Exceptions - `HTTPException` and `WebSocketException`

These are the exceptions that you can raise to show errors to the client.

When you raise an exception, as would happen with normal Python, the rest of the execution is aborted. This way you can raise these exceptions from anywhere in the code to abort a request and show the error to the client.

You can use:

* `HTTPException`
* `WebSocketException`

import org.apache.maven.artifact.Artifact;
import org.apache.maven.artifact.repository.ArtifactRepository;
import org.apache.maven.artifact.repository.ArtifactRepositoryFactory;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.plugin.LegacySupport;
import org.apache.maven.repository.MirrorSelector;
import org.apache.maven.settings.Mirror;
import org.apache.maven.settings.Proxy;

* Execution model
* Metadata model
* Metadata tooling
 ** Metadata extractor
 ** Metadata reader
 ** Metadata writer
 ** Metadata adapter (if required for the target system)
* Maven packaging and lifecycle
* Maven test harness for plugin execution model
* Eclipse IDE tooling for plugin execution model and metadata model

- we also seem to have information like the plugin lifecycle model that's buried inside the maven execution model

import org.apache.maven.api.services.VersionParser;
import org.apache.maven.api.services.VersionRangeResolver;
import org.apache.maven.execution.DefaultMavenExecutionResult;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.extension.internal.CoreExports;
import org.apache.maven.extension.internal.CoreExtensionEntry;

#if !defined(IS_MOBILE_PLATFORM)
  // Set up a multi-client distributed execution environment. Must be called on
  // all tasks in the cluster.
  // This call internally coordinates with other tasks to initialize the eager
  // context and TF server for multi-client execution.
  virtual absl::Status EnableCollectiveOps(const ServerDef& server_def) = 0;

import org.apache.maven.artifact.resolver.ArtifactNotFoundException;
import org.apache.maven.artifact.resolver.ArtifactResolutionException;
import org.apache.maven.execution.MavenExecutionRequest;
import org.apache.maven.execution.MavenSession;
import org.apache.maven.model.Repository;
import org.apache.maven.model.building.ModelBuildingException;
import org.apache.maven.model.building.ModelBuildingRequest;

            count = count + 1;

            validPluginCounts.put(pluginArtifactId, count);
        }

        assertNotNull(testPlugin);

        List<PluginExecution> executions = testPlugin.getExecutions();

        assertEquals(1, executions.size());
    }