MCS024 : Question 3 (b) Servlets and Session Handling in Java Web Applications | June 2023 Paper Solution

What is servlet ? Explain how session handling is performed in servlet programming.

Answer:

Servlet:

In Java, a servlet is a server-side technology used to extend the capabilities of web servers. It allows developers to create dynamic web applications that can handle client requests, process data, and generate dynamic content. Servlets are Java classes that follow the Java Servlet API and are deployed on a web server to handle HTTP requests and responses.

Session Handling in Servlet Programming:
Session handling is crucial in web applications to maintain user-specific data across multiple requests. In servlet programming, session handling is performed using the HttpSession interface provided by the Java Servlet API. HttpSession allows developers to create, manage, and store session data associated with a specific user session.


The process of session handling in servlet programming typically involves the following steps:

1. Creating a Session:
When a user accesses a web application, a session object is created to store user-specific data. The session can be created using the "getSession()" method of the HttpServletRequest object. If a session already exists, it is returned; otherwise, a new session is created.

2. Storing Data in Session:
Once a session is created, data can be stored in the session object using the "setAttribute()" method. This method takes a key-value pair, where the key is a string identifier and the value is the data to be stored. For example, 'session.setAttribute("username", "Lawtantra")' stores the username "Lawtantra" in the session.

3. Retrieving Data from Session:
To retrieve data from the session, the "getAttribute()" method is used. It takes the key as an argument and returns the corresponding value stored in the session. For example, 'String username = (String) session.getAttribute("username")' retrieves the value associated with the "username" key.

4. Updating and Removing Data from Session:
Data stored in the session can be updated by using the "setAttribute()" method again with the same key. To remove data from the session, the "removeAttribute()" method is used, passing the key of the data to be removed.

5. Invalidating a Session:
When a user logs out or the session needs to be terminated, the session can be invalidated using the "invalidate()" method. This removes all data stored in the session and marks it as no longer valid.


Session handling allows web applications to maintain user-specific data and state across multiple requests. It is essential for implementing features like user authentication, shopping carts, and personalized experiences in web applications. Servlets provide the HttpSession interface, which simplifies the process of session handling by providing methods to create, store, retrieve, update, and invalidate session data.