Java Servlets by Example: Lifecycle, Practical Implementations, and Best Practices (2025)

Did you know that Java is still among the top 3 most popular programming languages among developers in 2025? Its widespread use powers scalable enterprise applications, with the servlet program in java remaining a foundational technology for server-side web development.

A servlet program in Java uses a structured lifecycle, init, service, and destroy to manage concurrent HTTP requests with thread safety and efficient resource handling. This guide details lifecycle methods, deployment workflows, and best practices, including input validation and session management. 

You will also examine an example Java servlet showcasing dynamic response generation and error handling. Understanding these core concepts is essential for effective Java backend development in 2025.

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What Are Servlets in Java, and Why Are They Important?

Java servlets are server-side Java programs designed to handle client requests and generate dynamic content efficiently. They operate within a servlet container, managing HTTP protocols and supporting multithreading for high performance. Using Java servlets by example, you can build scalable web applications that integrate seamlessly with technologies like JavaScript and Node.js.

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• Role of Servlets: Java servlets act as intermediaries processing HTTP requests, enabling dynamic web pages and real-time client-server interactions essential for modern web architectures. They ensure smooth communication between front-end interfaces and backend servers.
• Advantages Over CGI: Unlike traditional CGI scripts, servlets support multithreading, reducing overhead and improving response times. This makes Java servlets by example ideal for resource-intensive applications requiring scalability and low latency.
• Types of Servlets: You’ll find generic servlets that handle protocol-independent requests and HTTP servlets optimized for web-specific functions. Knowing when to use each type helps you design flexible and effective applications.
• Building Applications: Servlets enable advanced features like session management, authentication, and integration with JavaScript frameworks or machine learning services for personalized user experiences. They form the backbone of enterprise-grade solutions.
• Enterprise-Level Use: Many enterprise applications rely on Java servlets for their stability and performance, handling thousands of simultaneous connections while ensuring secure and maintainable code.

Example Scenario

Suppose you are developing an e-commerce platform targeting Indian users that requires fast, dynamic product listings and personalized recommendations powered by machine learning. Using Java servlets by example, you can handle user sessions efficiently while integrating with JavaScript frontends and Node.js microservices. This approach ensures responsive performance and a smooth shopping experience.

Now, having a clear understanding of the fundamental aspects of Java servlets, let’s look at the architecture of Java servlets in detail. 

Understanding Java Servlet Architecture

The Java servlet architecture follows a strict request-response model where clients send HTTP requests, and servlets process these requests to generate dynamic responses. This model optimizes communication between clients and servers, making it fundamental for building interactive web applications. 

Using Java servlets, for example, you gain control over request handling with web technologies like HTML and scripting languages such as Bash scripting and PERL.

Here are some of the key components of Java Servlet Architecture:

• Servlet Container: This runtime environment manages servlet lifecycle phases, loading, initialization, request handling, and destruction. It also handles multithreading, ensuring efficient processing of concurrent client requests.
• Web Server: The web server acts as a gateway, forwarding client requests to the servlet container and delivering servlet-generated responses back to the client. It serves static content like HTML while delegating dynamic processing to servlets.
• Client-Server Interaction: Clients send HTTP requests via browsers or applications. Servlets interpret these requests, often parsing HTML forms or headers, and generate tailored responses, sometimes invoking shell scripts like Bash or PERL for backend processing.
• Types of Servlets: Generic servlets provide protocol-independent processing, while HTTP servlets specialize in handling HTTP-specific methods like GET and POST. Choosing the appropriate type enhances application flexibility.
• Servlet Programs in Java: Practical servlet implementations cover session tracking, user authentication, and real-time data management. For instance, you might integrate a Bash script for server maintenance tasks or use PERL scripts to handle data parsing alongside servlets.

Example Scenario

Imagine you’re building a customer support portal that collects input via HTML forms and processes it using servlets. By using Java servlets by example, you handle session management and validate user inputs securely. Meanwhile, you trigger Bash scripts for automated server health checks and utilize PERL scripts to process log files dynamically. This architecture ensures a responsive and maintainable web service tailored to your users’ needs.

Also read: 15 Essential Java Full Stack Developer Skills in 2025

Now, let’s explore Java's servlet classes and interfaces prominent within enterprise-related operations.

Java Servlet Classes and Interfaces: An Overview

In server-side Java programming, servlets form the backbone of dynamic web applications by processing client requests and generating real-time responses. Java servlets by example utilize core classes and interfaces that streamline development, support HTTP protocols, and enhance integration with front-end frameworks like ReactJS and backend databases like MySQL. 

Understanding these components ensures you can build scalable, maintainable applications with efficient database interactions using SQL queries.

• HttpServlet: Tailored for HTTP protocol handling, this class simplifies web application development by offering methods for GET, POST, PUT, and DELETE requests.
• GenericServlet: A protocol-agnostic class that provides the basic servlet structure, allowing customization beyond HTTP when necessary.
• Servlet Interface: Defines lifecycle methods (init(), service(), destroy()) essential for servlet management and resource handling.
• ServletConfig: Grants access to servlet initialization parameters, allowing you to customize behavior without hardcoding values.
• ServletContext: Offers a shared communication space among servlets within the same web application, enabling resource sharing and centralized configuration.

Code Example:

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

// The WelcomeServlet class extends HttpServlet to handle HTTP-specific requests
public class WelcomeServlet extends HttpServlet {

    // The doGet method handles GET requests from clients
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        // Setting the response content type to HTML
        response.setContentType("text/html");

        // Obtaining the PrintWriter object to write the response
        PrintWriter out = response.getWriter();

        // Writing the HTML response
        out.println("<html><body>"); // Starting the HTML document
        out.println("<h1>Welcome to Java Servlets!</h1>"); // Adding a heading
        out.println("<p>This is an example of a servlet program in Java using HttpServlet.</p>"); // Adding a paragraph
        out.println("</body></html>"); // Ending the HTML document
    }
}

Output:

<html>
  <body>
    <h1>Welcome to Java Servlets!</h1>
    <p>This is an example of a servlet program in Java using HttpServlet.</p>
  </body>
</html>

Output Explanation

When you access this servlet through a browser, it returns a clean HTML page with a heading confirming successful servlet execution. The paragraph briefly describes the servlet example, ensuring the response is clear and structured for further frontend or backend enhancements using ReactJS or MySQL.

Steps to Deploy Your Servlet

1. Compile the Servlet: Use javac to compile your servlet class and place the .class file in the WEB-INF/classes directory of your web application.
2. Configure Deployment Descriptor: Define your servlet and mapping in web.xml or use annotations (@WebServlet) for container-based discovery.
3. Deploy to Servlet Container: Run your application on containers like Apache Tomcat or Jetty, which manage the servlet lifecycle and request dispatching.
4. Access via Browser: Use a URL mapped to your servlet (e.g., http://localhost:8080/app/WelcomeServlet) to trigger the servlet and view the dynamic response.

Expected Output:

When this servlet is accessed via a browser using a GET request, the server responds with an HTML page containing the following:

• Heading: Displays "Welcome to Java Servlets!" as a bold, large-sized heading.
• Paragraph: A brief description, "This is an example of a servlet program in Java using HttpServlet," appears below the heading.
• HTML Structure: The response is formatted as a valid HTML document, rendered in the browser.

This output demonstrates a basic servlet generating dynamic web content.

How This Fits Into Modern Web Applications

When you pair servlets with ReactJS on the frontend, servlets handle backend processing and database communication using SQL with MySQL. For example, servlets can accept REST API calls from ReactJS, process data, query MySQL databases, and respond with JSON. This layered architecture promotes separation of concerns and scalability.

Now that you’ve learned about the key classes and interfaces let’s explore how you can handle HTTP requests and responses dynamically.

Handling HTTP Requests and Responses in Java Servlets

Java servlets are fundamental components in server-side programming that handle HTTP requests and responses for web applications. They efficiently process client data through GET and POST, enabling dynamic content generation and seamless integration with front-end technologies like CSS and backend languages like C++ and C#. By learning Java servlets by example, you can build scalable web services that communicate smoothly with diverse client environments and technologies.

• GET Requests: Designed to retrieve data from the server, GET requests include parameters in the URL. Servlets extract these query parameters and dynamically generate responses. This method is suitable for idempotent operations like search queries or data retrieval in C#-based web services.
• POST Requests: POST requests are used to submit sensitive or large amounts of data securely. They send parameters in the request body. Servlets validate and process form data or API payloads. This technique supports secure login systems, data uploads, or transactional operations, often interfaced with C++ backend systems.
• Servlet-JSP Communication: Servlets act as controller,s handling logic and forwarding requests to JSPs for presentation. JSPs, using CSS and JavaScript, render dynamic views with data passed via request attributes. This separation aligns with MVC architecture patterns common in enterprise applications combining Java servlets by example with front-end frameworks.
• Parameter Handling: The HttpServletRequest interface provides methods like getParameter() to retrieve client-sent data. Correct parsing of parameters ensures smooth integration with external components or services written in languages like C++ or C#.
• Response Generation: Using HttpServletResponse, servlets set content types (e.g., text/html) and send output via PrintWriter. This mechanism supports generating HTML with embedded CSS or JSON responses consumable by modern frontend frameworks.

Use Case:

Imagine developing a search portal that accepts queries via a ReactJS frontend styled with CSS. The servlet handles GET requests, extracts query parameters, and forwards results to JSP pages. Backend processing utilizes C++ modules for advanced search algorithms, while C# services manage user authentication via POST requests. Applying Java servlets by example, this architecture supports modular, scalable, and efficient communication across languages and technologies.

Let us now have a look at GET and POST one by one:

Processing GET Requests

GET requests are typically used to fetch data. Servlets can retrieve query parameters and generate responses dynamically.
Example: Handling a search request by retrieving user input from query parameters.

Code:

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class SearchServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String query = request.getParameter("query");

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html><body>");
        out.println("<h1>Search Results for: " + query + "</h1>");
        out.println("<p>Displaying results...</p>");
        out.println("</body></html>");
    }
}

Expected Output:

When the SearchServlet is accessed via a GET request with a query parameter (e.g., ?query=Java), the server responds with an HTML page containing:

• Heading: Displays "Search Results for: [query]" where [query] is the value provided in the URL (e.g., "Search Results for: Java").
• Paragraph: A placeholder message, "Displaying results...", indicating where search results would be displayed.
• HTML Structure: The response is formatted as an HTML document rendered in the browser.

This servlet demonstrates handling user input via query parameters and dynamically generating a web page based on the input.

Processing POST Requests

POST requests are used for submitting data securely. Servlets handle form submissions by validating and processing user inputs.
Example: Validating user login details.

Code:

import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");

        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<html><body>");
        if ("admin".equals(username) && "password123".equals(password)) {
            out.println("<h1>Welcome, " + username + "!</h1>");
        } else {
            out.println("<h1>Invalid Credentials</h1>");
        }
        out.println("</body></html>");
    }
}

Explanation of Parameters:

1. HttpServletRequest request:
   • Captures data sent by the client (e.g., form data like "username" and "password").
   • getParameter("name") retrieves specific form field values.
2. HttpServletResponse response:
   • Enables the servlet to send output (HTML in this case) back to the client.
   • setContentType("text/html") ensures the response is interpreted as an HTML page.

After understanding how to handle HTTP requests and responses, let’s see how you can enable seamless communication between servlets and JSPs.

Servlet-JSP Communication

Servlets can forward requests to JSPs using RequestDispatcher and share data with them.
Example: Forwarding user input to a JSP for display.

Code:

import java.io.IOException;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ForwardServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String message = "Hello from Servlet!";
        request.setAttribute("message", message);

        RequestDispatcher dispatcher = request.getRequestDispatcher("display.jsp");
        dispatcher.forward(request, response);
    }
}

JSP Code (display.jsp):
<%@ page language="java" contentType="text/html" pageEncoding="UTF-8"%>
<html>
<body>
    <h1>${message}</h1>
</body>
</html>

Expected Output:

When the ForwardServlet is accessed via a GET request:

1. In the Servlet (ForwardServlet):
   • A message, "Hello from Servlet!", is set as a request attribute (message).
   • The request is forwarded to display.jsp using RequestDispatcher.
2. In the JSP (display.jsp):
   • The JSP retrieves and displays the message attribute dynamically.

The output in the browser will show:
<h1>Hello from Servlet!</h1>

This servlet demonstrates how to forward requests to a JSP and pass data for dynamic rendering in the response.

With servlet-JSP communication covered, let’s explore how you can integrate servlets into the MVC architecture for cleaner application design.

MVC Architecture in Java

In Java web development, servlets often function as the controller within the Model-View-Controller (MVC) design pattern, managing client requests and coordinating data flow between the model and view. The Model layer contains business logic and data management, often connecting to databases using SQL or services implemented in languages like C++ or C#. 

The View uses JSP to render HTML interfaces styled with CSS. Implementing Java servlets by example in this pattern improves application modularity, scalability, and maintainability.

• Servlet as Controller: The servlet intercepts HTTP requests, processes input, interacts with the model to retrieve or update data, and selects the appropriate JSP for rendering the view.
• Model Layer: Encapsulates business logic, handles data persistence, and may interact with SQL databases such as MySQL or SQL Server, often using JDBC for communication.
• View Layer (JSP): Renders dynamic content using JSP expression language and integrates CSS for styling and JavaScript for interactivity, providing a rich user interface.
• Request Forwarding: Using RequestDispatcher, the servlet forwards request and response objects to JSPs, enabling clean separation between control logic and presentation.
• Integration with Other Technologies: This pattern supports integration with frontend frameworks like ReactJS and backend services written in C++ or C#, promoting flexible and modern web applications.

Code Example:

import javax.servlet.*;
import javax.servlet.http.*;
import java.io.IOException;

public class MVCServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String data = "Data from Model Layer";

        request.setAttribute("data", data);
        RequestDispatcher dispatcher = request.getRequestDispatcher("view.jsp");
        dispatcher.forward(request, response);
    }
}

Output:

<html>
<body>
    <h1>Model Data:</h1>
    <p>${data}</p>
</body>
</html>

Output Explanation

When the MVCServlet processes a GET request, it sets the data attribute and forwards the request to the view.jsp page. The JSP dynamically renders this data within an HTML structure, displaying the message inside the <p> tag. This separation ensures that business logic remains in the servlet, while presentation is handled by JSP, aligning with MVC principles.

The output in the browser will be:
<h1>Model Data:</h1>

<p>Data from Model Layer</p>

This example illustrates the Model-View-Controller (MVC) pattern, where the servlet acts as the controller, forwarding data to the JSP (view) for rendering.

Use Case:

Imagine you’re developing an enterprise dashboard where backend services written in C# and C++ handle complex computations and data aggregation. Using Java servlets by example, your servlet acts as the controller that fetches processed data from these services and forwards it to JSP views. This MVC approach allows your team to update business logic or UI components independently, enhancing scalability and maintainability in multi-technology environments.

Also Read: Java MVC Project [Step-By-Step Process Explained]

Having understood servlet classes and interfaces, let’s explore the types of Java servlets and how they address different application needs.

What Are the Different Types of Java Servlets?

Java servlets offer a flexible and efficient framework for server-side programming tailored to handle diverse web application needs. Servlet in Java are classified into two primary types: GenericServlet and HttpServlet. Each serves unique purposes, empowering developers to create versatile, scalable, and effective web applications that meet specific requirements. 

Let’s explore these servlet types in detail.

GenericServlet

GenericServlet is a protocol-agnostic foundation for developing servlets in Java. It offers unmatched flexibility for handling a wide range of client requests, regardless of the communication protocol.

Let’s have a look at its features and usage.

• Key Features:
  • Implements the Servlet interface for flexibility across protocols.
  • Requires manual implementation of the service() method.
• Use Cases: Ideal for lightweight applications or non-HTTP protocols where protocol-specific handling isn’t required.

Examples: 

• Email Systems (SMTP Protocol):
  A GenericServlet can process email-related data sent over the SMTP protocol, such as parsing messages or managing email queues.
• File Transfer Applications (FTP Protocol):
  Used in systems requiring FTP support, such as automated file uploads or downloads, without relying on HTTP.
• Custom Protocols for IoT Devices:
  Handles requests from IoT devices communicating over non-HTTP protocols, such as MQTT, ensuring seamless device-server interactions.

While GenericServlet lays the foundation for flexible request handling, many web applications require HTTP-specific capabilities. Let’s explore how HttpServlet fulfills these needs.

HttpServlet

HttpServlet is a specialized extension of GenericServlet designed to simplify HTTP-specific tasks. It provides predefined methods like doGet() and doPost(), enabling developers to focus on application logic without reinventing request-handling mechanisms.

Let’s have a look at its features and usage.

• Key Features:
  • Extends GenericServlet to include methods like doGet(), doPost(), doPut(), and doDelete().
  • Streamlines web application development with built-in HTTP handling.
• Use Cases: Widely used in modern web applications for handling form submissions, dynamic content generation, and session management.

Examples:

E-commerce Applications:

• Example: A servlet handles product searches and filter options on an e-commerce site.
• doGet(): Retrieves product details based on user queries.
• doPost(): Processes user input for orders or feedback.

Banking Portals:

• Example: Servlets power secure login systems and account management.
• doPost(): Handles customer login credentials securely.
• doPut(): Updates account details like phone numbers or addresses.

Content Management Systems (CMS):

• Example: Dynamic page generation based on user roles.
• doGet(): Serves pages like dashboards or reports.
• doDelete(): Deletes outdated articles or content.

Customer Support Systems:

• Example: A servlet processes user queries and escalates tickets.
• doPost(): Logs support tickets submitted via forms.
• doGet(): Retrieves ticket history for the user.

Also Read: Top 22 Open Source Java Projects to Enhance Your Development Skills

After exploring the types of Java servlets, let’s compare servlets with JSP to understand their unique roles and when to use each in web development.

Servlets vs JSP: When to Use Each?

In Java web development, servlets and JSP serve distinct but complementary roles. Servlets excel in handling backend business logic, managing requests, sessions, and database interactions, often running on platforms like AWS Lambda or Azure App Services. 

Conversely, JSP focuses on rendering dynamic web pages with embedded Java, CSS, and JavaScript for a responsive user interface. Combining them in an MVC architecture creates scalable, maintainable applications that integrate seamlessly with cloud services such as AWS and Azure Databricks.

Here’s a comprehensive difference among servlets, JSP, and combined MVC architectures:

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Steps to Write and Deploy Your First Servlet Program in Java: A Complete Execution Guide

Also read: Top 9 Machine Learning APIs for Data Science You Need to Know About

Developing and deploying your first servlet program in java is fundamental to learning server-side web programming. This process involves configuring a Java development environment, writing servlet code following the servlet lifecycle, and deploying it on a servlet container such as Apache Tomcat. Learning these steps equips you with essential skills in session management in servlet and error handling in servlet, enabling scalable web applications.

Step 1: Install and Configure JDK

• Download the latest Java Development Kit (JDK) from Oracle’s official site, ensuring compatibility with your operating system.
• Set environment variables JAVA_HOME and update the system PATH to enable compilation and execution of Java commands via the terminal or command prompt.

Step 2: Set Up an Integrated Development Environment (IDE)

• Install a Java IDE like Eclipse, IntelliJ IDEA, or NetBeans to facilitate code writing, debugging, and project management.
• Add servlet support plugins or modules if your IDE doesn’t include built-in support for Java EE web development.

Step 3: Install and Configure a Servlet Container

• Download Apache Tomcat, a widely used servlet container that implements the Java Servlet API to manage servlet lifecycle events and handle HTTP requests.
• Integrate Tomcat with your IDE by configuring it as a server runtime environment, allowing seamless deployment and debugging of your servlet program in Java.

Step 4: Verify Your Development Setup

• Develop a basic servlet following Java servlet example conventions—overriding doGet() or doPost() to send a simple response like “Hello, World!”
• Deploy the servlet to Tomcat via your IDE or by copying compiled classes to the appropriate web application directory.
• Access the servlet through a web browser using the configured URL pattern to confirm successful deployment and server response.

Example Scenario

Suppose you are tasked with building a user authentication module for a web application. Using your first servlet program in Java, you implement the servlet lifecycle methods to initialize resources and manage requests.

You integrate session management in servlet to track logged-in users and incorporate error handling in servlet to gracefully manage invalid login attempts. Deploying this on Apache Tomcat within your IDE allows for iterative testing and debugging, laying the groundwork for more complex enterprise-grade applications.

Writing your First Servlet Program

Creating your first servlet program in java introduces you to the core of server-side Java web development. This simple servlet responds to HTTP GET requests by sending a dynamic HTML response. Understanding this foundational example will help you grasp the servlet lifecycle and the basics of session management in servlet later on.

Here’s a step-by-step manner to write a servlet program in Java

1. Create a Java class extending HttpServlet.
2. Override the doGet() method to handle GET requests.
3. Set response content type to text/html.
4. Write HTML content to the response output stream.

Code Example:

import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloWorldServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        response.getWriter().println("<html><body><h1>Hello, World!</h1></body></html>");
    }
}

Output:

<html>
  <body>
    <h1>Hello, World!</h1>
  </body>
</html>

Output Explanation:

When you access this servlet via a web browser, it returns a well-formed HTML page displaying “Hello, World!” inside an <h1> tag. This confirms that the servlet successfully processed the GET request and sent dynamic content, demonstrating the essential behavior of a java servlet example.

Example Scenario:

Imagine you are beginning your journey in Java web development and want to verify your environment setup. Writing and deploying this servlet program in java helps you confirm that your server correctly handles HTTP requests. This foundational knowledge prepares you to implement more advanced features like session management in servlet and error handling in servlet.

Deploying your Program

Deploying your servlet program in java requires placing compiled classes correctly and configuring the deployment descriptor (web.xml). This configuration instructs the servlet container (e.g., Apache Tomcat) how to map URLs to your servlet, ensuring it’s accessible for HTTP requests.

Steps to Deploy

1. Place the compiled .class file into the WEB-INF/classes directory of your web application.
2. Configure web.xml to register the servlet and map its URL pattern.
3. Start the servlet container (Apache Tomcat) to host your application.
4. Access the servlet URL via a browser or API testing tool.

Code Example:

<web-app>
    <servlet>
        <servlet-name>HelloWorld</servlet-name>
        <servlet-class>HelloWorldServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>HelloWorld</servlet-name>
        <url-pattern>/hello</url-pattern>
    </servlet-mapping>
</web-app>

Output:

http://localhost:8080/YourAppName/hello

Output Explanation

Upon deployment, navigating to the URL mapped to /hello triggers the servlet’s doGet() method. The browser displays the “Hello, World!” message confirming that Tomcat correctly routes requests to your servlet, showcasing the servlet lifecycle from initialization to request handling.

Example Scenario

Consider deploying your first servlet program in java as part of a training exercise to understand deployment mechanics. Successfully configuring web.xml and accessing your servlet demonstrates proficiency in servlet configuration and lays the foundation for handling real-world tasks like integrating with AWS Lambda or Azure App Services.

Testing 

Testing your servlet program in java ensures it responds correctly to HTTP requests. You can verify functionality through standard web browsers or API testing tools like Postman, simulating GET requests and inspecting the responses.

1. Open a web browser, enter the servlet URL (/hello), and observe the output.
2. Use Postman or curl to send a GET request to the servlet URL and examine the raw response.
3. Check for correct content-type headers and valid HTML content in the response.

Code Example:

GET http://localhost:8080/YourAppName/hello

Output:

curl -X GET http://localhost:8080/YourAppName/hello

Output Explanation:

This GET request targets the URL pattern /hello mapped to your servlet in web.xml. When the servlet container (like Tomcat) receives this request, it invokes the doGet() method of your servlet program in java, which returns the dynamic HTML response "Hello, World!".

Deploying on Cloud Environment

Deploying your servlet program in Java to cloud platforms ensures scalability, high availability, and global accessibility. Cloud providers like AWS and Google Cloud Platform (GCP) offer managed infrastructure and services to efficiently host and run servlet-based applications. Using containerization with Docker, orchestration with Kubernetes, and streaming with Apache Kafka can further enhance deployment flexibility, resilience, and real-time data processing capabilities.

Here are the steps for deploying servlets to a cloud environment:

• Prepare the WAR File: Package your servlet application into a WAR file using IDEs like Eclipse or IntelliJ IDEA, ensuring all dependencies and configurations are included.
• Create an Application in Elastic Beanstalk: Log into the AWS Management Console, navigate to Elastic Beanstalk, and create a new Java application environment.
• Upload the WAR File: Select the Java platform and upload your WAR file. Elastic Beanstalk automates provisioning of resources, deployment, and load balancing.
• Access Your Application: Once deployed, Elastic Beanstalk provides a public URL to access your servlet application globally.

Code Example:

import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class HelloWorldServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        response.getWriter().println("<html><body><h1>Hello, World from Cloud Deployment!</h1></body></html>");
    }
}

Output:

<html>
  <body>
    <h1>Hello, World from Cloud Deployment!</h1>
  </body>
</html>

Output Explanation

Accessing the servlet URL hosted on AWS Elastic Beanstalk or GCP App Engine triggers the servlet's doGet() method, returning a dynamic HTML page confirming deployment. This response demonstrates proper handling of the servlet lifecycle within a cloud-managed servlet container, with opportunities to incorporate session management in servlet. 

Example Scenario

Suppose you develop a real-time analytics dashboard where servlets process incoming data streams, and Apache Kafka manages event-driven data flow. You containerize the application with Docker and orchestrate deployments using Kubernetes on AWS EKS. For example, you use Java servlets to deploy the servlet WAR to Elastic Beanstalk for global availability while integrating it with Kafka for asynchronous processing.

If you want to learn more about JavaScript, check out upGrad’s JavaScript Basics from Scratch. The 19-hour free certification will provide you with expertise on conditionals, variables, and more for organizational applications. 

Understanding the Lifecycle of a Java Servlet: From Initialization to Destruction

The servlet lifecycle in Java is designed to efficiently manage the creation, execution, and destruction of servlets, ensuring optimal use of server resources. This lifecycle has three primary stages: Initialization, Request Handling, and Destruction. Each stage plays a critical role in maintaining application stability and performance in various types of servlet.

Let’s dive into each stage in detail.

The Servlet Lifecycle Stages

The servlet lifecycle defines how your servlet program in java initializes, handles client requests, and cleans up resources. Learning these stages, Initialization, Request Handling, and Destruction is critical for efficient resource use, effective session management in servlet, and proper error handling in servlet. Understanding this lifecycle improves application performance and reliability.

Initialization (init() Method)

• Purpose: Called once when the servlet loads, used for resource allocation and setup.
• What Happens:
  • Servlet container calls init() before servicing requests.
  • Commonly initializes database connections or reads configuration.

Code Example:

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;

public class InitExampleServlet extends HttpServlet {
    @Override
    public void init(ServletConfig config) throws ServletException {
        super.init(config);
        System.out.println("Servlet initialized and ready to handle requests!");
    }
}

Output:

Servlet initialized and ready to handle requests!

Output Explanation:

When the servlet is loaded, the server logs the initialization message once, confirming the servlet setup phase completed successfully.

Request Handling (service() Method)

• Purpose: Processes each HTTP request, routing to methods like doGet() or doPost().
• What Happens:
  • Handles concurrent requests using multithreading.
  • Interacts with HttpServletRequest and HttpServletResponse to process input and generate output.

Code Example:

import java.io.IOException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServiceExampleServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
        response.setContentType("text/html");
        response.getWriter().write("<h1>Request Handled: GET Method</h1>");
    }
}

Output:

<h1>Request Handled: GET Method</h1>

Output Explanation:

When accessed via a browser or HTTP client, the servlet dynamically returns an HTML response indicating that the GET request was processed, demonstrating active request handling in the servlet lifecycle.

Destruction (destroy() Method)

• Purpose: Releases resources before servlet removal or server shutdown.
• What Happens:
  • Called once to clean up connections, threads, or cached data.

Code Example:

import javax.servlet.http.HttpServlet;

public class DestroyExampleServlet extends HttpServlet {
    @Override
    public void destroy() {
        System.out.println("Servlet is being destroyed. Cleaning up resources...");
    }
}

Output:

Servlet is being destroyed. Cleaning up resources...

Output Explanation:

This message logs when the servlet is unloaded, confirming resource cleanup aligned with proper error handling in servlet and lifecycle management.

Also read: Top 20 DevOps Practice Projects for Beginners with Source Code in 2025

Best Practices for Developing Java Servlets

Developing efficient and secure servlet programs in java demands adherence to best practices that enhance code maintainability, performance, and security. Proper project organization, input validation, and optimized resource management ensure your servlets handle requests reliably within the constraints of the servlet lifecycle. 

Using modern features like annotations and session management in servlet mechanisms strengthens your application’s resilience and user experience.

• Maintain an Organized Project Structure: Separate your source code, configuration files, and external dependencies into distinct directories. This modularization facilitates easier debugging, deployment, and collaboration in multi-developer environments.
• Ensure Input Validation and Sanitization:
  Validate all user inputs rigorously to guard against SQL injection, cross-site scripting (XSS), and other injection attacks. Use whitelist validation techniques and encode outputs to maintain security.
• Optimize Performance: Avoid heavy computations or blocking operations within servlets. Minimize synchronized blocks to prevent thread contention. Delegate intensive tasks to backend services or asynchronous processing frameworks when possible.
• Use Annotations Over XML Configuration:
  Adopt @WebServlet and other Java EE annotations to define servlets, reducing XML complexity and enhancing readability and maintainability.
• Implement Strong Session Management: Utilize HTTP sessions or secure cookies to maintain user state and context across multiple requests, ensuring seamless interaction and data integrity.
• Configure Logging and Monitoring: Integrate logging frameworks like Log4j or SLF4J to capture detailed runtime information. Effective logging aids in troubleshooting, performance tuning, and auditing.

Example Scenario

Consider you’re developing an e-commerce platform using a servlet program in java. By organizing your codebase clearly, you streamline feature updates and bug fixes. You validate all user inputs to protect against malicious payloads, apply @WebServlet annotations for cleaner deployment, and manage user sessions securely to personalize shopping experiences. Logging provides insights into user behavior and system health, aligning with production-grade application standards and supporting the servlet lifecycle effectively.

Also read: 50 Java Projects With Source Code in 2025: From Beginner to Advanced

How upGrad Can Help You Master Java Servlets and More?

Servlets in Java implement HTTP request handling through distinct servlet types and a precise lifecycle to enable scalable, efficient server-side web processing. Understanding servlet lifecycle stages, initialization, request handling, and destruction ensures efficient resource management and reliable performance. To optimize your servlet programs, implement effective session management, validate inputs rigorously, and use annotations for streamlined configuration.

If you want to gather expertise in Java and other programming tools. These are some of the additional courses of upGrad  that can help understand Java for software development and product deployment purposes. .

• Professional Certificate Program in Data Science and AI
• Data Structures & Algorithms
• Master the Cloud and Lead as an Expert Cloud Engineer

Curious which courses can help you gain expertise Java? Contact upGrad for personalized counseling and valuable insights. For more details, you can also visit your nearest upGrad offline center. 

How upGrad Can Help You Master Java Servlets and More?

upGrad offers tailored learning programs designed to help Java professionals deepen their knowledge and advance their careers. These programs focus on core concepts like servlets, JSP, and practical implementation, ensuring a hands-on approach to mastering Java development.

Here are a few programs to get you started:

• Professional Certificate Program in UI/UX Design & Design Thinking
• Job-Ready Full Stack Developer
• Executive Program in Generative AI for Leaders
• Post Graduate Certificate in Data Science & AI (Executive)

Program Benefits:

• Industry Mentorship: Learn from experienced professionals.
• Flexible Schedules: Study at your convenience.
• Real-World Projects: Build practical skills and a strong portfolio.

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References:
https://softjourn.com/insights/is-java-still-used