*
     * @return The model being built, never {@code null}.
     */
    Model getModel();

    /**
     * Gets the model building request being processed.
     *
     * @return The model building request being processed, never {@code null}.
     */
    ModelBuildingRequest getRequest();

    /**
     * Gets the container used to collect problems that were encountered while processing the event.

      sink.flush()
    }
  }

  /**
   * Tell the peer to stop creating streams and that we last processed `lastGoodStreamId`, or zero
   * if no streams were processed.
   *
   * @param lastGoodStreamId the last stream ID processed, or zero if no streams were processed.
   * @param errorCode reason for closing the connection.
   * @param debugData only valid for HTTP/2; opaque debug data to send.
   */

        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // despite all are back, we need to make sure all the events are processed (are async)
        // this one should block until all processed
        listener.transferSucceeded(new TransferEvent.Builder(session, resource)
                .setType(TransferEvent.EventType.SUCCEEDED)
                .build());

@Deprecated(since = "4.0.0")
public interface ModelPathTranslator {

    /**
     * Resolves the well-known paths of the specified model against the given base directory. Paths within plugin
     * configuration are not processed.
     *
     * @param model The model whose paths should be resolved, may be {@code null}.
     * @param basedir The base directory to resolve relative paths against, may be {@code null}.

        listener.transferInitiated(event(session, resource, TransferEvent.EventType.INITIATED));

        Thread.sleep(500); // to make sure queue is processed, cancellation applied

        // subsequent call will cancel
        assertThrows(
                TransferCancelledException.class,

    ModelBuildingRequest setPomPath(Path pomPath);

    /**
     * Gets the level of validation to perform on processed models.
     *
     * @return The level of validation to perform on processed models.
     */
    int getValidationLevel();

    /**
     * Sets the level of validation to perform on processed models. For building of projects,

// Progress message payload is an XML document containing information about the progress of a request.
//   - BytesScanned => Number of bytes that have been processed before being uncompressed (if the file is compressed).
//   - BytesProcessed => Number of bytes that have been processed after being uncompressed (if the file is compressed).
//   - BytesReturned => Current number of bytes of records payload data returned by S3.
//

  optional int64 observedGeneration = 1;

  // DisruptedPods contains information about pods whose eviction was
  // processed by the API server eviction subresource handler but has not
  // yet been observed by the PodDisruptionBudget controller.
  // A pod will be in this map from the time when the API server processed the
  // eviction request to the time when the pod is seen by PDB controller

 */
@Deprecated(since = "4.0.0")
public interface ModelBuildingListener {

    /**
     * Notifies the listener that the model has been constructed to the extent where build extensions can be processed.
     *
     * @param event The details about the event.
     */
    void buildExtensionsAssembled(ModelBuildingEvent event);

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.
* Then it passes the **request** to be processed by the rest of the application (by some *path operation*).