Servlets Tutorial for Beginners

This tutorial will teach you servlets in Java.
In this tutorial you'll learn:

• Desktop and web applications
• Installing and configuring Tomcat
• Http protocol and port numbers
• Servlet basics
• Generic and Http Servlets, form submissions
• Annotations in servlets
• Servlet communication
• Cookies
• Session Tracking

1. Desktop and web applications

You'll need to learn what are web apps before you start developing them.

• Desktop and web applications (including web design vs web development)

2. Installing and configuring Tomcat

To work with servlets, you need a web server. We will use Tomcat here. Download Tomcat 7 

• How to install tomcat in Windows? (includes setting classpath)

For every web application, we create a directory in Tomcat installation directory. So you need to know the typical folder structure for a tomcat web application.

• Folder structure for Tomcat

3. HTTP Protocol and port numbers

You need to learn what is HTTP protocol, static and dynamic pages before you develop any web application.

• Brief view of HTTP protocol (including static vs dynamic pages, HTTPS, hyper-text)
• Understanding port numbers (2-minute guide)

4.  Servlet basics

You'll need to learn the basics of Java servlets that help you ace the web development with Java.

• Basics of Java servlets (with disadvantages of CGI)

5. Generic and Http Servlets

Generic servlets are protocol-independent, it isn't just for http protocol.

Http servlets are strictly for http protocol.

• First servlet hello world app

There are two ways of sending data (aka making request or user input) from client to server. They are GET and POST.

GET transfers data via the address bar as query string. For example,
http://google.com/search?q=amazon

POST transfers data in background and hence not visible in the address bar. This is used for sending usernames and passwords as they must not be visible in the address bar.

• Difference between doGet() and doPost() in servlets
• Simple form submission in servlets using doGet()
• Handling choice in servlets
• Form submission using doPost

6. Annotations in servlets

We can use annotations in servlets. Annotation is data about a class or a member variable or a method that will be useful at run time.

• Servlet web application without web.xml 

7. Servlet communication

Servlets need to communicate with each other to transfer data from one servlet to another.

• Servlet to servlet communication (passing request object)  

8. Cookies

Cookies are key-value pairs that are stored in the web browser. As HTTP is a stateless protocol, there must be some way for the web application to keep track of the previous requests by the user. For example, in amazon.com while shopping, our items are stored in the cart though we move to other pages, we will be displayed the previous items that we have added. This is because, our previous data is stored. Where? In our browser only!

• Cookies in servlets with example

9. Session Tracking

Session tracking is an alternative to cookies. Cookies are stored in client browser, sessions are stored in server. What if cookies are disabled in browser? What if they are manually deleted? For all this, session tracking is the ultimate solution.

• Session tracking example in servlets