Java Servlets are a powerful technology for developing web applications in Java. Servlets are server-side components that receive and respond to requests from clients, typically web browsers. They can be used to dynamically generate web pages, process data submitted by users, and more. Here are some resources for learning about Java Servlets:

1. The Oracle Java Servlets tutorial: This tutorial provides an overview of Servlets, explains how to set up a development environment, and walks through building a simple Servlet-based web application. It also covers advanced topics such as filters and session management. You can find the tutorial at: https://docs.oracle.com/javaee/7/tutorial/servlets.htm

2. The Java Tutorials: This is a comprehensive set of tutorials covering a wide range of Java topics, including Servlets. The Servlets tutorial covers everything from the basics of creating a Servlet to more advanced topics such as handling multipart/form-data requests. You can find the tutorial at: https://docs.oracle.com/javase/tutorial/servlets/index.html

3. The Javatpoint Servlet tutorial: This tutorial provides a step-by-step guide to building Servlet-based web applications. It covers everything from the basics of Servlets to more advanced topics such as database connectivity and security. You can find the tutorial at: https://www.javatpoint.com/servlet-tutorial

4. Baeldung Servlet tutorial: Baeldung provides a number of tutorials covering various aspects of Java development, including Servlets. Their Servlet tutorial covers the basics of creating and deploying a Servlet, handling GET and POST requests, and working with cookies and sessions. You can find the tutorial at: https://www.baeldung.com/intro-to-servlets

5. Udemy Servlets and JSP tutorial: Udemy provides a comprehensive Servlet and JSP tutorial course that covers everything from the basics of Servlets and JSPs to more advanced topics such as building a complete web application. The course is designed for beginners to intermediate developers and includes hands-on coding exercises. You can find the course at: https://www.udemy.com/course/servlets-jsp-tutorial/