To handle HTML form data with a Java servlet, you can follow these steps:

1. Create a HTML form in your JSP or HTML page with the necessary input fields.

<form action="MyServlet" method="post">
  Name: <input type="text" name="name"><br>
  Email: <input type="email" name="email"><br>
  Message: <textarea name="message"></textarea><br>
  <input type="submit" value="Submit">
</form>

2. In your Java servlet, override the doPost method to handle the form data. This method is called when the form is submitted.

public class MyServlet extends HttpServlet {

  @Override
  protected void doPost(HttpServletRequest request, HttpServletResponse response)
      throws ServletException, IOException {

    // Get the form data from the request
    String name = request.getParameter("name");
    String email = request.getParameter("email");
    String message = request.getParameter("message");

    // Process the form data as needed
    // ...

  }

}

3. Inside the doPost method, use the HttpServletRequest object to get the form data that was submitted. You can use the getParameter method to retrieve the value of each input field.

4. Process the form data as needed. You can use the retrieved values to update a database, send an email, or perform any other action required by your application.

5. Once you have processed the form data, you can use the HttpServletResponse object to send a response back to the user, such as a thank you message or a redirect to another page.

response.sendRedirect("thankyou.html");

That's it! With these steps, you can handle HTML form data with a Java servlet and process it as needed in your application.