Java.Servlet.What is a “servlet”?

A servlet is a Java program that runs on a Java-enabled web server (like Apache Tomcat) and handles HTTP requests and responses. Servlets are part of the Java EE (Jakarta EE) platform and are used to create dynamic web content, such as web pages or data responses.

In simple terms:

A servlet is like a middleman between a web browser (client) and the server-side Java application logic.

🔧 How It Works (Simplified Flow):

1. Client sends an HTTP request (like clicking a button or submitting a form).
2. Web server receives the request and passes it to the servlet.
3. Servlet processes the request (e.g., fetches data from DB, does logic).
4. Servlet generates a response (often HTML or JSON).
5. Web server sends the response back to the browser.

📦 Servlet Lifecycle:

Managed by the Servlet container (like Tomcat):

1. init() – Initializes the servlet (called once).
2. service() – Called for each client request.
3. destroy() – Called before the servlet is removed from memory.

@WebServlet("/hello")
public class HelloServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
            throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("<h1>Hello, Stanley!</h1>");
    }
}

🧠 When a user visits http://yourserver/hello, this servlet is triggered and returns an HTML page with “Hello, Stanley!”