Servlet interview questions and answers Answers with example

Most Asking 50  Java Servlet interview questions and answers with example 

Other Technical Interview Questions and Answers

👉 Top 50 most asked interview questions and answers with examples

1. What is a Java Servlet?

A Java Servlet is a server-side component used to extend the capabilities of a web server, enabling the creation of dynamic web applications.

2. How do you create a Servlet?

To create a Servlet, you need to create a Java class that extends the javax.servlet.http.HttpServlet class and override its doGet() or doPost() method.

Example: 

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

public class MyServlet extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {

        // Servlet code here

    }

}

3. What is the difference between doGet() and doPost() methods in a Servlet?

doGet() is used for handling HTTP GET requests, while doPost() is used for handling HTTP POST requests.

4. What is the purpose of the init() method in a Servlet?

The init() method is used to perform one-time initialization tasks when the Servlet is first loaded by the server.

public void init() throws ServletException {

    // Initialization code here

}

5. Explain the purpose of the destroy() method in a Servlet.

The destroy() method is used to perform cleanup tasks when the Servlet is being unloaded by the server.

public void destroy() {

    // Cleanup code here

}

6. How do you configure a Servlet in a web application?

Servlets are typically configured in the web.xml file or using annotations (@WebServlet) in modern Servlet containers like Tomcat.

7. What is the web.xml file used for in a Servlet-based web application?

The web.xml file is a deployment descriptor used to configure Servlets, filters, and other web application components.

8. Explain the difference between Servlet and JSP.

Servlets are Java classes that generate HTML content dynamically on the server-side, whereas JSP (JavaServer Pages) is a technology that allows you to embed Java code within HTML to generate dynamic content more easily.

9. What is a Servlet container?

A Servlet container (also known as a Servlet engine) is a web server or application server that hosts and manages Servlets and provides runtime support for Servlet execution.

10. How can you pass data from a Servlet to a JSP page?

You can use the request attributes or session attributes to pass data from a Servlet to a JSP page.

11. Explain the difference between ServletContext and ServletRequest.

ServletContext represents the entire web application and is shared among all Servlets, while ServletRequest represents an individual HTTP request and is specific to a particular request.

12. What is the purpose of the ServletContext in a Servlet application?

ServletContext is used for sharing resources and information across Servlets in the same web application.

13. How can you retrieve a parameter from a request in a Servlet?

You can use the request.getParameter("parameterName") method to retrieve a parameter from an HTTP request.

String paramName = request.getParameter("paramName");

14. Explain the use of the RequestDispatcher in Servlets.

RequestDispatcher is used to forward or include a request to another Servlet or resource, allowing you to control the flow of the request within the server.

RequestDispatcher dispatcher = request.getRequestDispatcher("anotherServlet");

dispatcher.forward(request, response);

15. What is a Servlet filter, and why is it used?

A Servlet filter is a component that can intercept and manipulate requests and responses. Filters are used for tasks such as authentication, logging, and input validation.

16. How do you declare a filter in the web.xml file?

You can declare a filter in the web.xml file using the <filter> and <filter-mapping> elements.

<filter>

    <filter-name>MyFilter</filter-name>

    <filter-class>com.example.MyFilter</filter-class>

</filter>

<filter-mapping>

    <filter-name>MyFilter</filter-name>

    <url-pattern>/*</url-pattern>

</filter-mapping>

17. Explain the life cycle of a Servlet filter.

A Servlet filter goes through three stages: initialization, request processing, and destruction. The init() method is called during initialization, the doFilter() method processes requests, and the destroy() method is called during cleanup.

18. How can you handle exceptions in a Servlet application?

You can use error pages in the web.xml file to specify how to handle exceptions. For example:

<error-page>

    <exception-type>java.lang.Exception</exception-type>

    <location>/error.jsp</location>

</error-page>

19. What is session tracking in Servlets, and how can you achieve it?

Session tracking is the process of maintaining state information between multiple requests from the same client. You can achieve session tracking in Servlets using cookies, URL rewriting, and HttpSession.

20. Explain the use of the HttpSession interface in Servlets.

HttpSession allows you to store and retrieve session-specific data between multiple requests from the same client.

HttpSession session = request.getSession();

session.setAttribute("username", "John");

21. What are Servlet listeners, and what are their types?

Servlet listeners are interfaces that allow you to respond to events in a Servlet's life cycle. The main types of listeners are ServletContextListener, HttpSessionListener, and ServletRequestListener.

22. How can you create a custom Servlet listener?

To create a custom Servlet listener, you need to implement one of the listener interfaces and override the appropriate methods.

23. Explain the Single Thread Model in Servlets.

The Single Thread Model is an interface in Servlets that ensures that only one thread is executed at a time for a particular instance of a Servlet. However, it's deprecated in modern Servlet specifications.

24. What is the purpose of the @WebServlet annotation in Servlet 3.0 and later versions?

The @WebServlet annotation is used to define a Servlet in a more concise and modern way, eliminating the need for web.xml configuration.

@WebServlet(name = "MyServlet", urlPatterns = {"/myServlet"})

public class MyServlet extends HttpServlet {

    // Servlet code here

}

25. How can you handle file uploads in a Servlet?

You can handle file uploads in a Servlet using libraries like Apache Commons FileUpload or Servlet 3.0's Part interface.

26. Explain the purpose of the setContentType() method in a Servlet response.

The setContentType() method sets the MIME type of the response, indicating the type of content that will be sent to the client.

response.setContentType("text/html");

27. How do you send a redirect response from a Servlet to another URL?

You can send a redirect response using the response.sendRedirect("url") method.

response.sendRedirect("https://example.com");