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Introduction to Java Servlets

Java Servlets are server-side Java programs that handle HTTP requests and generate dynamic web content. They form the foundation of Java web applications and are widely used in enterprise systems across the United States, Europe, and Australia.

What Are Java Servlets?

A Servlet is a Java class that extends the capabilities of servers hosting applications accessed via a request-response programming model. When a user visits a URL, the web container (such as Apache Tomcat) receives the HTTP request and forwards it to the appropriate Servlet, which processes the request and returns a response—typically HTML, JSON, or a redirect.

Why Learn Servlets?

  • Servlets are the core of Java EE/Jakarta EE web stacks used by banks, government, and Fortune 500 companies.
  • Understanding Servlets helps you master Spring MVC, Spring Boot, and Jakarta REST under the hood.
  • Servlet concepts—HTTP methods, sessions, filters—apply directly to modern API development.
  • Strong Servlet knowledge is valued in Java developer interviews in the US, UK, and Australia.

Servlet Architecture Overview

Web Browser

Sends HTTP requests (GET, POST) to the server when users interact with a web application.

Web Container (Tomcat)

Receives requests, manages Servlet lifecycle, and provides servlet API implementations.

Servlet

Java class that handles business logic and generates dynamic responses.

Database / Services

Servlets often connect to JDBC, REST APIs, or message queues for data.

Basic Servlet Example

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

Servlet vs JSP

Servlets contain Java code with embedded HTML, while JSP (JavaServer Pages) embed Java inside HTML. Modern applications often use Servlets as controllers and JSP or template engines for views. Spring Boot abstracts much of this, but the underlying request handling remains Servlet-based.

Frequently Asked Questions

Are Java Servlets still used in 2025?▼

Yes. While Spring Boot is the dominant framework, it runs on an embedded Servlet container. Legacy enterprise apps and many government systems still use Servlets directly. Understanding them is essential for Java web developers.

What do I need to run Servlets locally?▼

Install JDK 17 or later and Apache Tomcat (or use an IDE like IntelliJ IDEA or Eclipse with built-in Tomcat support). Deploy your WAR file or run from your IDE.

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