Asynchronous processing reduces thread blocking, allowing the server to handle more requests without waiting for each to complete, thus improving resource utilization.

The AsyncListener plays a role in monitoring asynchronous operations, allowing developers to respond to events such as the start and completion of asynchronous tasks or handling errors in asynchronous processing.

Asynchronous processing can extend the servlet lifecycle, as it allows tasks to continue beyond the usual request-response cycle, providing more flexibility in handling long-running operations.

The startAsync() method is called to initiate asynchronous processing in a servlet.

The dispatch() method of AsyncContext is used to dispatch the request to another servlet during asynchronous processing.

The primary use of RequestDispatcher in servlets is for forwarding requests to another resource (servlet, JSP, or HTML) on the server.

The primary interface used for file upload in servlets is ServletFileUpload. It provides a simple way to parse and process HTTP requests with content type multipart/form-data.

For file download, the Content-Type in the servlet response should be set to application/octet-stream to indicate that the response contains binary data without any specific format.

The HTTP status code 200 OK is typically sent by an HTTP servlet to indicate a successful response. This status code signals that the request has been successfully processed, and the server is returning the requested resource.

To retrieve an AsyncContext object in a servlet, you use the getAsyncContext() method of the HttpServletRequest.