Blog

Servlets play a fundamental role in Java-based web development. Despite the rise of frameworks like Spring Boot and Jakarta EE, understanding servlet interview questions is essential for Java developers, especially when working with backend services, web containers, or legacy systems.

This guide provides a comprehensive collection of commonly asked servlet questions and detailed answers, suitable for both freshers and experienced professionals. We’ll also explore servlet architecture, lifecycle, and real-world scenarios that interviewers love to test.

---

📘 What Is a Servlet?

A Servlet is a Java class that runs in a servlet container (like Apache Tomcat) and responds to client requests, typically HTTP. It’s a core component of Java EE (now Jakarta EE), enabling dynamic web content.

---

✅ Benefits of Using Servlets

Here are some advantages that make servlets foundational in Java web development:

1. Platform Independent – Written in Java, servlets run on any server with a servlet container.
2. Efficient and Scalable – Handles concurrent requests using threads, not processes.
3. Secure – Integrates with Java’s robust security model and supports HTTPS.
4. Extensible – Can be enhanced through filters and listeners.
5. Integrates Well with JSP – Often used alongside JSPs for MVC-based web apps.
6. Portable – Deployable across any servlet-compliant container like Tomcat, Jetty, or GlassFish.
7. Customizable HTTP Handling – Developers can manage requests/responses precisely.

---

🌱 Servlet Interview Questions for Freshers

1. What is a servlet in Java?

A servlet is a Java program that extends the capabilities of servers that host applications accessed via a request-response model, usually HTTP.

2. What are the lifecycle methods of a servlet?

There are three main lifecycle methods:

• init() – Initializes the servlet.
• service() – Processes client requests.
• destroy() – Cleans up resources before shutdown.

3. What is the difference between doGet() and doPost()?

• doGet() is used for retrieving data (idempotent requests).
• doPost() is used for sending data securely (form submissions).

4. What is a servlet container?

A servlet container (like Tomcat) is a part of a web server or application server that provides the runtime environment for Java servlets.

5. How do you configure a servlet?

There are two ways:

• Web.xml (deployment descriptor)
• Annotations like @WebServlet("/path") introduced in Servlet 3.0+

6. What is the role of web.xml?

web.xml is the deployment descriptor that maps servlets, filters, listeners, and other configuration in older servlet-based applications.

7. What are ServletConfig and ServletContext?

• ServletConfig provides configuration for a specific servlet.
• ServletContext shares data across the entire web application.

---

💼 Servlet Interview Questions for Experienced Developers

8. How do servlets handle multithreading?

By default, the servlet container uses a single instance of the servlet class and creates a new thread for each request. Proper synchronization is required for shared resources.

9. What is the use of filters in servlets?

Filters can intercept and modify requests and responses. Common use cases include:

• Logging
• Authentication
• Compression
• Content transformation

@WebFilter("/secure/*")
public class AuthFilter implements Filter {
    public void doFilter(...) {
        // Authentication logic
    }
}

10. What is a listener in Java Servlets?

A listener monitors events in a servlet’s lifecycle (e.g., app context initialization). Examples include Listener, HttpSessionListener.

11. How do you manage sessions in servlets?

Sessions are managed using HttpSession. You can retrieve or create a session using:

HttpSession session = request.getSession();

Session tracking can be done via:

• Cookies
• URL rewriting
• Hidden form fields

12. Explain request dispatching.

The RequestDispatcher interface allows forwarding a request to another resource or including its output in the response.

RequestDispatcher rd = request.getRequestDispatcher("nextPage.jsp");
rd.forward(request, response);

13. What is URL rewriting in servlets?

URL rewriting appends session ID or parameters to a URL to maintain state without cookies.

response.encodeURL("dashboard.jsp");

14. What are common HTTP methods supported by servlets?

• GET
• POST
• PUT
• DELETE
• HEAD
• OPTIONS
  Each maps to a method like doGet() or doPost() in HttpServlet.

15. How do you upload a file using a servlet?

Use @MultipartConfig annotation and parse Part objects from the request.

@MultipartConfig
@WebServlet("/upload")
public class UploadServlet extends HttpServlet {
   protected void doPost(HttpServletRequest req, HttpServletResponse res) {
      Part file = req.getPart("file");
      file.write("/uploads/" + file.getSubmittedFileName());
   }
}

---

🔁 Advanced Servlet Topics

• Asynchronous Servlets: Introduced in Servlet 3.0, allows non-blocking request processing.
• Servlets with JDBC: Frequently tested in real-world interview scenarios.
• Security in Servlets: Using HTTPS, input validation, and deployment descriptor-based authentication.
• Error Handling: Custom error pages via web.xml or @WebServlet error mappings.

---

📌 Servlet Shortcuts and Best Practices

• Use annotations over XML for modern applications.
• Avoid using instance variables to prevent concurrency issues.
• Close resources (JDBC, streams) in finally or use try-with-resources.
• Keep servlet logic thin; delegate business logic to separate classes.
• Cache expensive resources (e.g., DB connections via connection pools).

---

📊 Servlet vs JSP vs Spring MVC

Feature	Servlet	JSP	Spring MVC
Type	Java Class	HTML + Java	Java Framework
Control Flow	Manual	Page-based	Annotation-driven
Reusability	Moderate	Low	High
Separation of Concerns	Low	Low	High
Learning Curve	Moderate	Low	Steep (but modern)

While servlets are powerful and foundational, many modern apps use Spring MVC or RESTful APIs, but servlet knowledge remains crucial for technical interviews.

---

🙋‍♂️ FAQ: Servlet Interview Questions

Q1: Do I need to learn servlets in 2025?

Yes! While frameworks abstract them, servlets are the foundation of most Java web frameworks. Understanding them helps you master technologies like Spring.

Q2: What’s the latest version of the Servlet API?

As of 2025, Servlet 6.0 (Jakarta Servlet) is the most recent major release under Jakarta EE 10, replacing older Java EE-based packages.

Q3: Are servlets used in microservices?

Not directly. Microservices typically use lightweight frameworks like Spring Boot or Micronaut, but under the hood, they often leverage servlet containers like Tomcat.

---

📝 Final Thoughts

Servlets may not be the flashiest technology in the Java ecosystem, but they are the foundation of modern web application development. Whether you’re targeting a legacy enterprise job or simply building solid fundamentals for frameworks like Spring or JSF, mastering servlet interview questions is a must.

Use this guide to refresh your knowledge, practice code snippets, and gain the confidence to ace your Java interview.